Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Keiji Tanaka Last modified date:2021.06.23

Professor / Applied Fine Chemistry / Department of Applied Chemistry / Faculty of Engineering


Papers
1. Yihao Wu, Atsuomi Shundo, Yuji Yasukochi, Keiji Tanaka, Time-dependent Heterogeneity in Polyacrylic Pressure Sensitive Adhesive, European Polymer Journal, 10.1016/j.eurpolymj.2020.109812, 134, 2020.06.
2. Yukari Oda, Daisuke Kawaguchi, Yuma Morimitsu, Satoru Yamamoto, Keiji Tanaka, Direct Observation of Morphological Transition for an Adsorbed Single Polymer Chain, Scientific Reports, 10.1038/s41598-020-77761-0, 10, 20914, 2020.12, A better understanding of the structure of polymers at solid interfaces is crucial for designing various polymer nano-composite materials from structural materials to nanomaterials for use in industry. To this end, the first step is to obtain information on how synthetic polymer chains adsorb onto a solid surface. We closely followed the trajectory of a single polymer chain on the surface as a function of temperature using atomic force microscopy. Combining the results with a full-atomistic molecular dynamics simulation revealed that the chain became more rigid on the way to reaching a pseudo-equilibrium state, accompanied by a change in its local conformation from mainly loops to trains. This information will be useful for regulating the physical properties of polymers at the interface..
3. Satoru Yamamoto, Keiji Tanaka, Molecular Size Effect on Curing Process for Epoxy and Amine Mixture, Nihon Reoroji Gakkaishi, 10.1678/rheology.49.55. , 49, 2, 55-60, 2021.04.
4. Tatsuki Abe, Daisuke Kawaguchi, Motonori Watanabe, Taiki Hoshino, Tatsumi Ishihara, Keiji Tanaka, An Effect of Crystallographic Distortion on Carrier Mobility in Poly(3-​hexylthiophene) Thin Films, Applied Physics Letters, 10.1063/5.0041881, 118, 18, 181601-1-181601-5, 2021.05.
5. Fengliang Wang, Zhenwei Jiang, Xuanyu Lin, Cuiyun Zhang, Keiji Tanaka, Biao Zuo, Wei Zhang, Xinping Wang, Suppressed Chain Entanglement Induced by Thickness of Ultrathin Polystyrene Films, Macromolecules, 10.1021/acs.macromol.1c00224, 54, 8, 3735-3743, 2021.04, The thickness effect on the relaxation behavior and chain entanglements was investigated for thin polystyrene films. By following the time evolution of the wetting ridge at the surface induced by a droplet of ionic liquid, the characteristic time (tau*) at which the ridge height started to change was obtained. Here, we demonstrated experimentally that the characteristic time was associated with the disentanglement time tau(d), tau* similar to tau(d) similar to M-w(3.4)/M-e(1.4), where M-e denotes the entanglement molecular weight. The critical thickness (h(c)) at which tau* started to decrease was approximately 3.3R(g). That is, the M-e increased, or the interchain entanglement density decreased, as the film became thinner than the h(c). This might be explained in terms of the conformational change from "spherical" to "ellipsoidal", leading to a reduction in the pervaded volume (V-p) of chains in the ultrathin films..
6. Seungjae Lee, Wooseop Lee, Norifumi L. Yamada, Keiji Tanaka, Jong Hak Kim, Hoyeon Lee, Du Yeol Ryu, Instability of Polystyrene Film and Thermal Behaviors Mediated by Unfavorable Silicon Oxide Interlayer, Macromolecules, 10.1021/acs.macromol.9b01284, 52, 19, 7524-7530, 2019.10, Instability, glass transition temperature (T-g), and thermal expansion of polystyrene (PS) films are evaluated with respect to the thickness of a silicon oxide (SiOx) interlayer that mediates favorable long-range interaction from the non-oxide Si substrate. Taking into account that a SiOx interlayer is less favorable with an overlying PS film, we designed a systematic set of H-passivated (H-Si), native SiOx (N-Si), and non-native SiOx interlayer (P-Si) substrates. Here, P-Si denotes a substrate prepared by a plasma surface activation with oxygen to create an effective minimum SiOx thickness (similar to 9 nm) that is sufficient for the instability of PS films. The wetting-dewetting behavior differs in 100 and 43 kg/mol PS films supported on the three different substrates. Reflected in T-g and thermal expansion coefficient at the rubbery state for the overlying PS films, P-Si is found to be enough to promote the nontrivial instability of the films, leading to a marked decrease in T-g and increase in alpha(r) with decreasing film thickness (more than those on N-Si). Our results demonstrate the ability to use P-Si to effectively modulate favorable long-range interaction from the Si substrate better than a typical N-Si does..
7. Yuji Matsumoto, Atsuomi Shundo, Hisato Hayashi, Nobutomo Tsuruzoe, Keiji Tanaka, Effect of the Heterogeneous Structure on Mechanical Properties for a Nanocellulose-Reinforced Polymer Composite, Macromolecules, 10.1021/acs.macromol.9b01866, 52, 21, 8266-8274, 2019.11, Nanocellulose (NC), which consists of a bundled structure of cellulose chains, is a class of shape-anisotropic materials with a diameter of several tens of nanometers and a length of over several hundreds of nanometers. Because the production of NC is based on the extraction process from natural resources in water, NC is generally obtained in an aqueous dispersion state. Thus, an aqueous dispersion of NC can be regarded as a precursor for NC-reinforced polymer composites. The objective of this study is to gain a better understanding of (1) local rheological properties of the NC aqueous dispersion at various length scales using a particle tracking measurement and (2) how they affect the mechanical properties of the resultant NC-reinforced polymer composite. The observation of individual particles at different positions revealed that the NC aqueous dispersion was spatially heterogeneous at the characteristic length of a few tens of micrometers. When the NC aqueous dispersion was sonicated and subsequently left undisturbed at room temperature, the length scale of the heterogeneity decreased. From the NC aqueous dispersion with and without the sonication treatment, having smaller and larger length scale of heterogeneity, respectively, poly(vinyl alcohol) (PVA) films containing NC were fabricated. The dispersion state of NC in the PVA matrix was improved by the prior sonication treatment. The addition of NC remarkably enhanced the ductility of the PVA film. However, this was the case only after the sonication treatment. The knowledge here obtained should provide a novel concept for polymer composites with tunable mechanical properties, based on the precursor-based design..
8. Makoto Ouchi, Christine K. Luscombe, Junpo He, Keiji Tanaka, Special issue: Precision Polymer Synthesis, Polymer Journal, 10.1038/s41428-019-0276-2, 52, 1, 1-1, 2020.01.
9. Yuma Morimitsu, Hisao Matsuno, Noboru Ohta, Hiroshi Sekiguchi, Atsushi Takahara, Keiji Tanaka, Mechanical Stabilization of Deoxyribonucleic Acid Solid Films Based on Hydrated Ionic Liquid, Bio Macro Molecules, 10.1021/acs.biomac.9b01207, 21, 2, 464-471, 2020.02.
10. Satoru Yamamoto, Riichi Kuwahara, Mika Aoki, Atsuomi Shundo, Keiji Tanaka, Molecular Events for an Epoxy-Amine System at a Copper Interface, ACS Applied Polymer Materials, 10.1021/acsapm.9b01154, 2, 4, 1474-1481, 2020.04.
11. Tsukasa Miyazaki, Noboru Miyata, Tessei Yoshida, Hiroshi Arima, Yoshihiro Tsumura, Naoya Torikai, Hiroyuki Aoki, Katsuhiro Yamamoto, Toshiji Kanaya, Daisuke Kawaguchi, Keiji Tanaka, Detailed Structural Study on the Poly(vinyl alcohol) Adsorption Layers on a Si Substrate with Solvent Vapor-Induced Swelling, Langmuir, 10.1021/acs.langmuir.9b03964, 36, 13, 3415-3424, 2020.04.
12. Yukari Oda, Manabu Inutsuka, Ryo Awane, Masayasu Totani, Norifumi L. Yamada, Masayuki Haraguchi, Masaaki Ozawa, Hisao Matsuno, Keiji Tanaka, A Dynamic Interface Based on Segregation of an Amphiphilic Hyperbranched Polymer Containing Fluoroalkyl and Oligo(ethylene oxide) Moieties, Macro Molecules, 10.1021/acs.macromol.9b02064, 53, 7, 2380-2387, 2020.04.
13. Keiji Tanaka, PJ ZEON Award for outstanding papers in Polymer Journal 2019, Polymer Journal, 10.1038/s41428-020-0329-6, 52, 6, 551-553, 2020.06.
14. Masato Ikeda, Akinori Kuzuya, Michiya Matsusaki, Keiji Tanaka, Special issue: Biofunctional gels, Polymer Journal, 10.1038/s41428-020-0360-7, 52, 8, 821-821, 2020.08.
15. Kiminori Uchida, Kazuki Mita, Satoru Yamamoto, Keiji Tanaka, Local Orientation of Polystyrene at the Interface with Poly(methyl methacrylate) in Block Copolymer, ACS Macro Letters, 10.1021/acsmacrolett.0c00638, 9, 11, 1576-1581, 2020.11, The local conformation of polystyrene (PS) at the phase-separated lamellar interface with poly(methyl methacrylate) (PMMA) in their diblock copolymer (BCP) was examined by sum-frequency generation spectroscopy in conjunction with a full-atomistic molecular dynamics simulation. While PS phenyl groups of BCP were oriented in the interfacial region, they were random in the bulk. Such an interfacial orientation of phenyl groups was not clear for the corresponding blend of PS and PMMA. The PS backbone of BCP was in-plane oriented and folded near to the chemical junction point located in the interfacial region and the orientation became random at several nanometers distant. No evidence for the chain folding at the interface was found for the blend system..
16. Jin-Hyeok Hong, Masayasu Totani, Daisuke Kawaguchi, Norifumi L. Yamada, Hisao Matsuno and Keiji Tanaka , Poly[oligo(2-ethyl-2-oxazoline) methacrylate] as a Surface Modifier for Bioinertness, Polymer Journal, 10.1038/s41428-020-00459-7, 53, 5, 643-653, 2021.01.
17. Satoru Yamamoto, Keiji Tanaka, Entropy-Driven Segregation in Epoxy-Amine Systems at a Copper Interface, Soft Matter, 10.1039/D0SM01600D, 17, 5, 1359-1367, 2020.12.
18. J.-H. Hong, M. Totani, D. Kawaguchi, H. Masunaga, N. L. Yamada, H. Matsuno, and K. Tanaka, Design of a Bioinert Interface Using an Amphiphilic Block Copolymer Containing a Bottlebrush Unit of Oligo(oxazoline), ACS Applied Bio Materials, 10.1021/acsabm.0c01118, 3, 11, 7363-7368, 2020.12.
19. Takuro Kogo, Atsuomi Shundo, Chi Wang and Keiji Tanaka, Spatial Heterogeneity Accompanying Gel Formation of Poly(N-isopropylacrylamide) Aqueous Solution at a Temperature below Cloud Point, Macromolecules, 10.1021/acs.macromol.0c02292, 53, 24, 10964-20971, 2020.11.
20. Shinichiro Shimomura, Hisao Matsuno, Yohei Kinoshita, Satoshi Fujimura, Keiji Tanaka, Cellular behaviors on polymeric scaffolds with 2D-patterned mechanical properties, Polymer Journal, 10.1038/s41428-018-0043-9, 50, 8, 737-743, 2018.08, We propose a novel concept for cellular scaffolds with 2D-patterned mechanical properties. Thin films of glassy polystyrene (PS) with thicknesses ranging from 100 nm to 1 mu m were prepared on epoxy resin-based line and space (L&S) patterned substrates. Although the outermost surface of PS on the L- and S-regions was sufficiently flat at the same level, the mechanical responses differed depending on the presence of the underlying resin foundation. The initial cell adhesion and spreading and the proliferation on the scaffolds were affected by the 2D-patterned mechanical properties, that is, cellular behavior was suppressed on mechanically unstable S-regions..
21. Hidenobu Taneda, Atsuomi Shundo, Hisao Matsuno, Keiji Tanaka, Design of a Well-Defined Polyrotaxane Structure on a Glassy Polymer Surface, Langmuir, 10.1021/acs.langmuir.7b03130, 34, 2, 709-714, 2018.01, The polymer dynamics at the water interface play a crucial role in the manifestation of biorelated functions. One of the strategies for this is to form inclusion complexes of polymer chains with cyclic compounds. However, such an idea has been limited to bulk materials so far. Here we propose a preparation pathway for a polyrotaxane structure composed of poly(ethylene oxide) (PEO) and a-cyclodextrin (CD) at the outermost surface of a glassy poly(methyl methacrylate) film on the basis of the combination of a click reaction and the Langmuir-Blodgett method. The chain motion of PEO at the water interface could be regulated by threading of CD molecules on PEO and thereby the biological responses such as protein adsorption and platelet adhesion altered depending on the extent of complexation..
22. Hisao Matsuno, Shunya Irie, Toyoaki Hirata, Ruriko Matsuyama, Yukari Oda, Hiroyasu Masunaga, Yukiko Seki, Sadahito Aoshima, Keiji Tanaka, Heterogeneous adhesion of cells on polymer surfaces with underlying amorphous/crystalline phases, Journal of Materials Chemistry B, 10.1039/c7tb03250a, 6, 6, 903-907, 2018.02, Fibroblastic adhesion behaviour on films of a poly[(2-methoxyethyl vinyl ether) (PMOVE)-block-(L-lactic acid) (PLLA)], in which the surface was covered with PMOVE, was studied. Fibroblasts were sufficiently sensitive to identify crystalline/non-crystalline regions existing beneath the surface PMOVE layer..
23. Yuji Matsumoto, Atsuomi Shundo, Masashi Ohno, Nobutomo Tsuruzoe, Masahiro Goto, Keiji Tanaka, Mesoscopic Heterogeneity in Pore Size of Supramolecular Networks, LANGMUIR, 10.1021/acs.langmuir.8b00641, 34, 25, 7503-7508, 2018.06, There has been a considerable interest in developing new types of gels based on a network of fibrous aggregate composed of low molecular weight gelators, also known as supramolecular gels (SMGs). Unlike conventional polymer gels with chemical cross-linking, the network formation in SMGs does not involve any covalent bonds. Thus, the network in SMGs has been often regarded as homogenous or less heterogeneous in comparison with that in chemically cross-linked polymer gels. In this study, we have experimentally verified the existence of the network heterogeneity even in SMGs. The thermal motion of probe particles in SMGs, which were prepared from aqueous dispersions of gelators having a different number of peptide residues, PalGH, PalG(2)H, and PalG(3)H, was tracked. The gels were spatially heterogeneous in terms of the network pore size, as evidenced by the variation in the particle motion depending on the location, at which a particle existed. With varying particle size, it was found that the characteristic length scale of the heterogeneity was in the order of (sub)micrometers and was smaller in the order of the PalG(2)H, PalG(3)H, and PalGH gels..
24. Shinichiro Shimomura, Hisao Matsuno, Kazuaki Sanadac, Keiji Tanaka, Cell adhesion on glassy scaffolds with a different mechanical response, JOURNAL OF MATERIALS CHEMISTRY B, 10.1039/c6tb02617f, 5, 4, 714-719, 2017.01, L929 mouse fibroblast cells were cultured on bilayer films composed of a glassy poly(methyl methacrylate) (PMMA) on a rubbery polyisoprene. When the thickness of the upper PMMA film fell short of a threshold value of 50 nm, the adhesion of fibroblasts on it was remarkably suppressed. A possible explanation is that the surface of a bilayer with an ultrathin PMMA layer apparently becomes softer due to the manifestation of a mechanical response from the rubbery layer underneath. Finite element analysis shows that the shear stress at the bilayer surface induced by traction force of the attached cells is dependent on the PMMA thickness, similar to the cell adhesion behavior. These results make it clear that fibroblasts can sense the surface stiffness of polymers with a modulus even on the order of MPa..
25. Hung Kim Nguyen, Manabu Inutsuka, Daisuke Kawaguchi, Keiji Tanaka, Depth-resolved local conformation and thermal relaxation of polystyrene near substrate interface, JOURNAL OF CHEMICAL PHYSICS, 10.1063/1.4976523, 146, 20, 2017.05, By means of sum-frequency generation spectroscopy, we report a depth-resolved measurement of the local conformation and chain relaxation of polystyrene (hPS) located at different distances from the quartz interface. To control the distance from the quartz interface, deuterated polystyrene (dPS) layers with thicknesses of 3.4, 7.5, and 20 nm were coated on the quartz substrates. The hPS chains in direct contact with the substrate surface predominantly orient their phenyl rings in a direction normal to the substrate. This conformation was found to be barely relaxed when the film was annealed for 24 h at 423 K, higher than the bulk glass transition temperature. In contrast, for the hPS chains supported on the dPS layer, the orientation of phenyl rings of hPS became weaker with the annealing and this trend was more significant with increasing distance from the quartz substrate. In particular, the orientation of phenyl rings of hPS after annealing vanished at a distance of 20 nm. These results might provide an important evidence of the difference in the relaxation dynamics of the PS chains located at different distances from the quartz interface. Published by AIP Publishing..
26. Yuji Matsumoto, Atsuomi Shundo, Masashi Ohno, Nobutomo Tsuruzoe, Masahiro Goto, Keiji Tanaka, Evolution of heterogeneity accompanying sol-gel transitions in a supramolecular hydrogel, SOFT MATTER, 10.1039/c7sm01612c, 13, 40, 7433-7440, 2017.10, When a peptide amphiphile is dispersed in water, it self-assembles into a fibrous network, leading to a supramolecular hydrogel. When the gel is physically disrupted by shaking, it transforms into a sol state. After aging at room temperature for a while, it spontaneously returns to the gel state, called sol-gel transition. However, repeating the sol-gel transition often causes a change in the rheological properties of the gel. To gain a better understanding of the sol-gel transition and its reversibility, we herein examined the thermal motion of probe particles at different locations in a supramolecular hydrogel. The sol obtained by shaking the gel was heterogeneous in terms of the rheological properties and the extent decreased with increasing aging time. This time course of heterogeneity, or homogeneity, which corresponded to the sol-to-gel transition, was observed for the 1st cycle. However, this was not the case for the 2nd and 3rd cycles; the heterogeneity was preserved even after aging. Fourier-transform infrared spectroscopy, small-angle X-ray scattering, and atomic force and confocal laser scanning microscopies revealed that, although the molecular aggregation states of amphiphiles both in the gel and sol remained unchanged with the cycles, the fibril density diversified to high and low density regions even after aging. The tracking of particles with different sizes indicated that the partial mesh size in the high density region and the characteristic length scale of the density fluctuation were smaller than 50 nm and 6 mm, respectively..
27. Hisao Matsuno, Ryota Tsukamoto, Yukari Oda, Keiji Tanaka, Platelet adhesion on the surface of a simple poly(vinyl ether), POLYMER, 10.1016/j.polymer.2017.01.036, 116, 479-486, 2017.05, A better understanding of controlling factors in the control of bio-events on polymer surfaces is the first benchmark toward realization of life innovation. Although it has been accepted that a family of poly(vinyl ether) (PVE) with various side chain structures is a good candidate for a blood compatible material, the reasons are not fully understood. In this study, poly(vinyl ether) with a simple side chain structure, poly(ethyl vinyl ether) (PEVE), was studied. Since the glass transition temperature of PEVE is lower than room temperature, its thin films can be difficult to prepare. Thus, PEVE was mixed with a glassy polymer of poly(p-vinylphenol) (PVPh). The aggregation states of polymer chains and water molecules at the interface were characterized by the interfacial sensitive spectroscopy. The relationship between the structural information and the platelet adhesion behavior is discussed. This leads to a hypothesis that the states of water molecules affect platelet adhesion and activation behaviors on PVE. (C) 2017 Elsevier Ltd. All rights reserved..
28. Shin Sugimoto, Yukari Oda, Toyoaki Hirata, Ruriko Matsuyama, Hisao Matsuno, Keiji Tanaka, Surface segregation of a branched polymer with hydrophilic poly[2-(2-ethoxy)ethoxyethyl vinyl ether] side chains, POLYMER CHEMISTRY, 10.1039/c6py01984f, 8, 3, 505-510, 2017.01, A poly[2-(2-ethoxy) ethoxyethyl vinyl ether] macromonomer with a terminal vinyl group synthesized by living cationic polymerization was successively copolymerized with methyl methacrylate by atom transfer radical polymerization. The branched polymer mixed into poly(methyl methacrylate) was preferentially segregated at the film surface, leading to an anti-biofouling polymer surface..
29. Tomonori Ono, Kaoru Kawasaki, Keiji Tanaka, Toshihiko Nagamura, Ultrafast photoresponsive materials for all-optical light modulation by polymer thin films, POLYMER, 10.1016/j.polymer.2017.02.051, 116, 523-533, 2017.05, Ultrafast and single exponential responsive materials were achieved by encapsulating donor-acceptor linked molecules into cucurbitunitl[8], CB[8], as nanocavity hosts. Various aromatic groups were linked with various types of 4,4'-bipyridinium groups through propyloxy linker. They showed characteristic charge-transfer (CT) absorption with specific colors in aqueous solutions. Upon addition of CB[8], they showed remarkably different colors due to intramolecular CT complex formation in CB[8]. Upon femtosecond laser excitation of CT band extremely fast electron transfer occurred from a donor to an acceptor unit accompanying new absorption in the visible to near-infrared region due mainly to photoreduced bipyridinium derivatives. Thermal back electron transfer reactions in CB[8] were found to follow a single exponential decay with rate constants ranging more than two orders depending on the combination of a donor and an acceptor unit. Their rate constants vs. free energy changes for oxidized donors and reduced acceptors in linked molecules were expressed by the Marcus theory. (C) 2017 Elsevier Ltd. All rights reserved..
30. Yukari Oda, Cui Zhang, Daisuke Kawaguchi, Hisao Matsuno, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Design of Blood-Compatible Interfaces with Poly(vinyl ether)s, ADVANCED MATERIALS INTERFACES, 10.1002/admi.201600034, 3, 12, 2016.06.
31. Mani Sen, Naisheng Jiang, Justin Cheung, Maya K. Endoh, Tadanori Koge, Daisuke Kawaguchi, Keiji Tanaka, Flattening Process of Polymer Chains Irreversibly Adsorbed on a Solid, ACS MACRO LETTERS, 10.1021/acsmacrolett.6b00169, 5, 4, 504-508, 2016.04, We report the structural relaxation process of irreversibly adsorbed polymer chains via thermal annealing that lie flat on a solid ("flattened chains"). Amorphous polystyrene and quartz, which together constitute a weakly attractive system, was used as a model where the local chain conformations of the flattened chains were investigated by sum frequency generation spectroscopy (SFG). Two different film preparation processes (i.e., spin coating and dip coating methods) were utilized to create different initial chain conformations. The spin-coated and dip-coated PS thin films were annealed at a temperature far above the bulk glass transition temperature to reach the "quasiequilibrium" state and subsequently rinsed with chloroform to uncover the buried flattened chains. The SFG results revealed that the backbone chains (constituted of CH and CH2 groups) of the flattened PS chains preferentially orient to the weakly interactive substrate surface via thermal annealing regardless of the initial chain conformations, while the orientation of the phenyl rings becomes randomized. We postulate that increasing the number of surface-segmental contacts (i.e., enthalpic gain) is the driving force for the flattening process of the polymer chains, even onto a weakly interactive solid to overcome the conformational entropy loss in the total free energy..
32. Yukari Oda, Daisuke Kawaguchi, Toyoaki Hirata, Norifumi L. Yamada, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Density Profiles of Well-Defined Poly(methyl 2-propenyl ether) (PMPE) Near Water Interface, MACROMOLECULAR SYMPOSIA, 10.1002/masy.201400031, 350, 1, 99-104, 2015.04, Poly(methyl 2-propenyl ether) (PMPE) is structually different in terms of the presence of an alpha-methyl group on the main chain from poly(vinyl methyl ether) (PVME), the phase behaviors of which have been widely characterized with polystyrene (PS) and water. Due to the incorporation of the alpha-methyl group, PMPE is immiscible with both PS and water. These results encouraged us to investigate a PMPE/water interface more closely. Thus, the density profiles of PMPE in the vicinity of the water interface were probed by neutron reflectivity (NR) measurement. Even in the presence of the alpha-methyl group on the main chain, PMPE slightly swelled near the water interface. The obtained results will give us an insight into a better design and construction of the polymers for several bioapplications..
33. Cui Zhang, Yukari Oda, Daisuke Kawaguchi, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Dynamic-driven Surface Segregation of a Hydrophilic Component in Diblock Copolymer Films, CHEMISTRY LETTERS, 10.1246/cl.140924, 44, 2, 166-168, 2015.02, We here show how a hydrophilic component can be stably partitioned to the film surface of multicomponent polymer systems using well-designed diblock copolymers..
34. Hisao Matsuno, Ruriko Matsuyama, Arisa Yamamoto, Keiji Tanaka, Enhanced cellular affinity for poly(lactic acid) surfaces modified with titanium oxide, POLYMER JOURNAL, 10.1038/pj.2015.30, 47, 7, 505-512, 2015.07, A surface modification method of biocompatible poly(lactic acid) (PLA) with titanium oxide (TiOx) is proposed. Tetraethoxytitanium(IV) (TEOT) was used to construct a TiOx network with a few residual ethyl groups via an acid-catalyzed sol-gel reaction exploiting surface segregation. The surface of the resulting PLA-TiOx composite films was flat and homogeneous when the TEOT loading was <5 wt%. The properties of the PLA-TiOx composite films were examined by microscopy to explore the fibroblast affinity for the scaffold surface. The number of cells attached to the PLA-TiOx composite films increased with increasing surface TiOx content. Cell morphology was also dependent upon the surface TiOx content, and the attached cells on the composite film were better spread than those on the pristine PLA film. These results clearly show that our proposed method is a useful technique to improve the affinity of cells for PLA surfaces..
35. Hoyeon Lee, Seongjun Jo, Toyoaki Hirata, Norifumi L. Yamada, Keiji Tanaka, Eunkyoung Kim, Du Yeol Ryu, Interpenetration of chemically identical polymer onto grafted substrates, POLYMER, 10.1016/j.polymer.2015.07.054, 74, 70-75, 2015.09, Interpenetrating interfaces between a deuterated polystyrene (dPS) and the grafted substrates with the same chemical identity were characterized using neutron reflectivity (NR) measurements, where the PSgrafted substrates were prepared using a grafting-to approach with hydroxyl end-functionalized polystyrene (PSOH) in a dry brush regime. The characteristic brush thickness (h(d)) and grafting density (sigma) of PS-grafted layers were determined based on the chain length (or molecular weight, M-n) of PSOHs. The experimental interpenetration length (zeta) was measured at the interfaces, and the limiting plateau in x above which the value was independent of film thickness shifted toward higher values as the M-n of PSOH increased. Normalization by the deformed brush thickness (h(d)) of PS-grafted layer after interpenetration revealed that the experimental value of zeta/h(d) in a short and dense PS-grafted substrate, prepared with a low-molecular-weight PSOH, deviated markedly from the theoretical value, indicating significant additional stretching of the grafted chains to accommodate inter-mixing with the dPS chains. (C) 2015 Elsevier Ltd. All rights reserved..
36. Tisato Kajiyama, Hirohiko Yakabe, Daisuke Kawaguchi, Atsushi Takahara, Keiji Tanaka, Melting behavior of thin polyethylene films, JOURNAL OF PLASTIC FILM & SHEETING, 10.1177/8756087915594418, 31, 4, 401-413, 2015.10, Melting behavior in thin films of linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) was studied by local thermal analysis (mu TA). Even in the films thinner than 100nm, the melting temperature (T-m) was successfully observed by mu TA. For LLDPE, T-m decreased as the thickness became thinner than 150nm. For HDPE, T-m increased with decreasing thickness. Polarized infrared spectroscopy revealed that an edge-on lamellar structure formed in both cases, meaning that the crystallite orientation may not be a reason why the thickness dependence of T-m was not the same for both resins. A possible explanation is that for LLDPE the segmental mobility in the amorphous region predominates with decreasing thickness, and for HDPE the chain orientation in the region predominates with decreasing thickness..
37. Yukari Oda, Ayanobu Horinouchi, Daisuke Kawaguchi, Hisao Matsuno, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Effect of Side-Chain Carbonyl Groups on the Interface of Vinyl Polymers with Water, LANGMUIR, 10.1021/la404802j, 30, 5, 1215-1219, 2014.02, The nature of the polymer-water interface in the poly(methyl 2-propenyl ether) (PMPE)-water model system is investigated by sum-frequency generation spectroscopy, which at the moment gives the best depth resolution among available techniques. PMPE, synthesized via living cationic polymerization, is structurally similar to poly(methyl methacrylate) (PMMA) except for lacking a carbonyl group. We here probe the polymer local conformation as well as the aggregation states of water at the interface. Comparing the results of our measurements to the PMMA-water system, the effect of a carbonyl group on the water structure at the interface is discussed. This knowledge should be crucial to the design and construction of highly functionalized polymer interfaces for bioapplications..
38. Jie Zhan, Hisao Matsuno, Hiroyasu Masunaga, Hiroki Ogawa, Keiji Tanaka, Green solid films with tunable mechanical properties made from deoxyribonucleic acid, NPG ASIA MATERIALS, 10.1038/am.2014.4, 6, 2014.03, Promoting green innovation to establish a worldwide low-carbon society is an urgent priority. Effective utilization of natural resources excluding fossil fuels is one of the efforts that will contribute to the resolution of this issue. Here, we show that solid-state films made from deoxyribonucleic acid (DNA) can be used as a structural material. The great advantage of the DNA films over the ones made from synthetic polymers is that the mechanical properties are controllable, from glassy to rubbery, via semicrystalline by simply regulating the water content in the film. Why and how such unique mechanical properties can be manifested by the DNA films is determined from detail structural analyses using Fourier-transform infrared spectroscopy and wide-angle X-ray diffraction measurements. With an increasing water content, the conformation of double-stranded DNA (dsDNA) was changed from the A-form in an amorphous state to the B-form in a partially packed one. dsDNA in the B-form became densely packed as the film was stretched..
39. Hirofumi Tsuruta, Yukari Ikinaga, Yoshihisa Fujii, Keiji Tanaka, A simple approach for surface hardening of polystyrene, APPLIED SURFACE SCIENCE, 10.1016/j.apsusc.2012.10.070, 264, 589-592, 2013.01, One strategy in prolonging the lifetime of polymer materials is to improve their surface mechanical properties. A simple and easy method to modify the polymer surface based on the preferential segregation of inorganic materials is applied to a glassy polymer. We clearly show that the polystyrene film with a few nm-thick hybrid surface layer with hydrolyzed tetraethoxysilane exhibits excellent wear resistance and anti-oxidant properties. (C) 2012 Elsevier B.V. All rights reserved..
40. Atsuomi Shundo, Koichiro Hori, Takuya Ikeda, Nobuo Kimizuka, Keiji Tanaka, Design of a Dynamic Polymer Interface for Chiral Discrimination, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 10.1021/ja404701s, 135, 28, 10282-10285, 2013.07, Enantioselective wetting of a chiral polymer film was demonstrated. The contact angle of chiral liquids on the film was strongly dependent on their chirality although their physical properties including surface tension were identical. Such wetting behavior resulted from the enantioselective surface reorganization involving local conformational change of the polymer chains at the liquid interface. The concept of "dynamic interface for chiral discrimination" has possible potential for the development of materials capable of chiral sensing, optical resolution, and asymmetric synthesis..
41. Atsuomi Shundo, David P. Penaloza, Keiji Tanaka, Microscopic heterogeneity in viscoelastic properties of molecular assembled systems, CHINESE JOURNAL OF POLYMER SCIENCE, 10.1007/s10118-013-1193-z, 31, 1, 1-11, 2013.01, An important step in understanding molecular assembled systems is to examine the structure and physical properties at various length scales and clarify the correlation between them. However, while the structures of these systems have been extensively studied from nanoscopic to macroscopic scales, their viscoelastic properties have been often limited to bulk rheological measurements. By using optical tweezers and particle tracking, we here show the local viscoelastic properties and their spatial distributions for the following systems: worm-like micelle solution, supramolecular hydrogel and lyotropic liquid crystal, which are formed by self-assembly of amphiphilic molecules in water. We found that all systems studied possessed a spatial heterogeneity in their viscoelastic properties and this was originated from the heterogeneous structures. It is interesting to note that there is the heterogeneity with the characteristic length scale of sub-micrometer or micrometer scale, thereby structures, although the systems are formed by molecules with nanometer size. The findings of these studies should lead to a better understanding of the dynamics of such systems..
42. Cui Zhang, Yoshihisa Fujii, Keiji Tanaka, Effect of Long Range Interactions on the Glass Transition Temperature of Thin Polystyrene Films, ACS MACRO LETTERS, 10.1021/mz300391g, 1, 11, 1317-1320, 2012.11, The glass transition temperature (T-g) of thin polystyrene (PS) films supported on silicon wafers with oxide layers of varying thickness was characterized by the temperature dependence of the film thickness using ellipsometry. This allowed us to uncover how a long-range interaction affects the T-g of polymer films. As previously reported using a variety of methods, the T-g decreased with decreasing film thickness. However, the extent was not the same among the reports. In this study, we found that the T-g attenuation of a PS film of a given thickness was dependent on the oxide layer thickness of the silicon wafer via the long-range interaction..
43. Atsuomi Shundo, Yohei Okada, Fuyuki Ito, Keiji Tanaka, Fluorescence Behavior of Dyes in Thin Films of Various Polymers, MACROMOLECULES, 10.1021/ma201901x, 45, 1, 329-335, 2012.01, We have studied the fluorescence behavior of a dye, 6-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoic acid (NBD), in thin films of polymers with various polarities, such as poly(methyl rnethacrylyate) (PMMA), Arton, poly(styrene) (PS), hydrogenated polystyrene (H-PS), and Zeonex. In the case of well-dispersed systems,.the fluorescence behavior of NBD could - be explained in terms of the mobility of the polymer matrix. This was the case for PMMA, Arton, and PS. On the other hand, when H-PS or Zeonex was.used, NBD aggregated in the films, leading to unusual fluorescence behavior: the fluorescence lifetime and maximum wavelength increased with a decrease in the film thickness. Time- and space-resolved fluorescence spectroscopy using an evanescent wave excitation revealed that the aggregation states of NBD near the interface varied with the film thickness, While NBD molecules near the interface aggregated in a thick film, such was not the case in a thin film. Angular dependent X-ray photoelectron spectroscopy (ADXPS) structurally confirmed the above observations; that is, the film thickness greatly influenced the depth profile of the NBD composition in the polymer films..
44. Hirofumi Tsuruta, Yoshihisa Fujii, Naoki Kai, Hiroshi Kataoka, Takashi Ishizone, Masao Doi, Hiroshi Morita, Keiji Tanaka, Local Conformation and Relaxation of Polystyrene at Substrate Interface, MACROMOLECULES, 10.1021/ma3007202, 45, 11, 4643-4649, 2012.06, The local conformation of polymer chains in a film at a substrate interface was examined by sum-frequency generation spectroscopy. When a polystyrene (PS) film was prepared on a quartz substrate by a spin-coating method, the chains were aligned in the interfacial plane of the substrate. A dissipative particle dynamics simulation revealed that a spinning torque induced the chain orientation during the film preparation process and the extent of the orientation was a function of the distance from the interface. This interfacial orientation of chains was not observed for a PS film prepared by a solvent-casting method. Interestingly, the local conformation of chains at the substrate interface was unchanged even at a temperature that was 80 K higher than the bulk glass transition temperature (T-g). This observation means that polymer chains at the substrate interface can be only partially relaxed under conditions where the bulk chains are fully relaxed. On the other hand, interfacial chains could be easily relaxed by solvent annealing..
45. Akihiro Matsubayashi, Kenji Fukunaga, Tetsuro Tsuji, Kikuo Ataka, Hisashi Ohsaki, Keiji Tanaka, Band-selective Mirror Characteristics of Polymer/Metal Multilayer Films, CHEMISTRY LETTERS, 10.1246/cl.2011.1138, 40, 10, 1138-1139, 2011.10, The optical characteristics of polymer/metal composite films having metal nanoparticles periodically aligned in rows were explored. They were prepared by irradiating ultraviolet light on the polymer films containing metal complex spin-coated on a reflective surface. The films were found to exhibit band-selective mirror characteristics. The wavelength of maximum reflection can be controlled by changing the incident angle of the irradiating light..
46. Hisao Matsuno, Jun-ichi Nakahara, Keiji Tanaka, Dynamic Mechanical Properties of Solid Films of Deoxyribonucleic Acid, BIOMACROMOLECULES, 10.1021/bm1010933, 12, 1, 173-178, 2011.01, Solid films of deoxyribonucleic acid (DNA) from salmon testes were prepared by a solvent-casting method. The thermal molecular motion of the DNA film was examined by dynamic mechanical analysis (DMA). Four absorption peaks and one shoulder of the loss modulus were observed in the temperature domain from approximately 150 to 490 K. To assign these, thermal analysis employing thermogravimetry (TG) and differential thermal analysis (DTA) was used in cc junction with ultraviolet (UV)-visible and Fourier-transform infrared (FT-IR) spectroscopy. It seems most likely that, in order of increasing temperature, they are a B-I -> B-II, conformational transition, a relatively large-scale movement associated with water molecules, water evaporation, thermal denaturation of DNA, and a glass transition..
47. Satoshi Miwa, Takako Kikuchi, Yoshito Ohtake, Keiji Tanaka, Surface degradation of poly(ethylene-co-propylene-co-5-ethylidene-2-norbornene) terpolymer by ozone in water, POLYMER DEGRADATION AND STABILITY, 10.1016/j.polymdegradstab.2011.05.001, 96, 8, 1503-1507, 2011.08, Saturated olefinic rubbers have been widely used as materials for not only municipal waterworks, but also for household uses. As a sanitizing agent for water, chlorine will be replaced by ozone in the near future from an environmental point of view. However, the ozone treatment in water seriously damages saturated olefinic rubbers, which are necessary for the infrastructure of daily life. Here, we report the surface degradation of cross-linked poly(ethylene-co-propylene-co-5-ethylidene-2-norbornene) terpolymer (EPDM) by ozone treatment, both in water and air. We also discuss how the presence of water impacts the ozone oxidation of EPDM, resulting in macroscopic damage to EPDM. (C) 2011 Elsevier Ltd. All rights reserved..
48. Daisuke Kawaguchi, Keisuke Masuoka, Atsushi Takano, Keiji Tanaka, Toshihiko Nagamura, Naoya Torikai, Robert M. Dalgliesh, Sean Langridge, Yushu Matsushita, Comparison of interdiffusion behavior between cyclic and linear polystyrenes with high molecular weights, MACROMOLECULES, 10.1021/ma060652t, 39, 16, 5180-5182, 2006.08.
49. Structures and Physical Properties at Surfaces and Interfaces of Polymers.
50. Molecular Aggregation Structure of Polymer Materials at the Water Interface and Its Biocompatibility.
51. Yongming Hong, Yawei Li, Fengliang Wang, Biao Zuo, Xinping Wang, Li Zhang, Daisuke Kawaguchi, Keiji Tanaka, Enhanced Thermal Stability of Polystyrene by Interfacial Noncovalent Interactions, MACROMOLECULES, 10.1021/acs.macromol.8b01012, 51, 15, 5620-5627, 2018.08, The local conformation of polystyrene (PS) and deuterated PS at the interface with quartz substrates, which were covered with phenyl groups using phenyltrimethoxysilane (PTS) under various conditions, was examined by sum frequency generation spectroscopy. As evidenced by the red-shift of the wavenumber of the v(2) vibration mode for phenyl groups, it was claimed that PTS phenyl groups standing vertically from the quartz surface induced the perpendicular orientation of PS phenyl rings by energetically favorable parallel-displaced pi-pi interactions at the interface. The local conformation of PS chains strongly anchored onto the substrate by the pi-pi interactions remained almost unchanged for 48 h even at a temperature 60 K higher than the bulk glass transition temperature. That is, the interfacial pi-pi interactions facilitated the adsorption of PS chains on the substrate to attain a large enthalpic gain, resulting in significantly slower dynamics of PS chains at the interface. Our results illustrate the importance of the interfacial noncovalent interactions in controlling the structure and dynamics of macromolecular chains at the interface as well as in the thin film geometry..
52. Load-induced frictional transition for well-defined cyclic self-Assembled monolayers
© 2018 Japanese Society of Tribologists. All rights reserved. Self-Assembled monolayer (SAM) with amphiphilic linear molecules has been studied as a surface modifier. In general, the surface properties of a SAM are dependent on the chain end chemistry of the molecules. Thus, a SAM composed of alkane loops from cyclic alkanedisulfide on a gold substrate, in which both sulfurs arc bound to gold, may possess unique surface properties due to the chain folding as well as a lack of chain ends. We here focus on the frictional properties of the linear and cyclic SAMs. For the cyclic SAM, the load dependence of the frictional force became more striking beyond a threshold. Such a frictional transition was not observed for the corresponding linear SAM. The load-induced transition in the frictional response from the alkane loops could be related to the conformational change of the alkane loops, which collapsed along the direction normal to the SAM surface..
53. Keiji Tanaka, Koichi Shimakawa, Mechanisms of photoinduced fluidity in chalcogenide glasses: Molecular orbital analyses, JOURNAL OF NON-CRYSTALLINE SOLIDS, 10.1016/j.jnoncrysol.2017.12.005, 481, 579-584, 2018.02, Atomic processes giving rise to the photoinduced fluidity have been studied for amorphous selenium. Ab initio molecular orbital calculations of Se clusters suggest that distorted atomic structures such as curled and intersecting chains have smaller optical gaps. Those atomic sites are likely to be excited by subgap (Urbach-edge) light, which undergo structural relaxation including bond breakages and interchanges. Such photo-electro-structural transformations could originate the macroscopic fluidity. Possibility of electronic glass-transition is also discussed..
54. Keiji Tanaka, A Polaronic View of Impact Ionization in Amorphous Se Films, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 10.1002/pssr.201700254, 11, 10, 2017.10, In this letter, it is proposed that the impact ionization in amorphous Se films, which triggers avalanche carrier multiplications, occurs through transformations of electron and hole motions from polaronic to supersonic states, the situation resembling those envisaged for semiconducting one-dimensional organic polymers. However, reflecting unique origins of the conduction and the valence band in Se, the electron-lattice interaction appears stronger than the hole-lattice interaction, which seems to be responsible for characteristic properties such as less efficient electron multiplication. The idea is consistent with the fact that a-Si:H having three-dimensional structures exhibits no corresponding phenomena..
55. Deborah A. Barkley, Naisheng Jiang, Mani Sen, Maya K. Endoh, Jonathan G. Rudick, Tadanori Koga, Yugang Zhang, Oleg Gang, Guangcui Yuan, Sushil K. Satija, Daisuke Kawaguchi, Keiji Tanaka, Alamgir Karim, Chain Conformation near the Buried Interface in Nanoparticle-Stabilized Polymer Thin Films, MACROMOLECULES, 10.1021/acs.macromol.7b01187, 50, 19, 7657-7665, 2017.10, It is known that when nanoparticles are added to polymer thin films, they often migrate to the film-substrate interface and form an "immobile interfacial layer", which is believed to be the mechanism behind dewetting suppression. We here report a new mechanism of dewetting suppression from the structural aspect of polymer chains accommodated at the film substrate interface. Dodecanethiol-functionalized gold (Au) nano-particles embedded in relatively low molecular weight PS thin films prepared on silicon (Si) substrates were used as a model. We mimicked the previously reported conditions, where the nano particles preferentially migrate to the substrate, and successfully stabilized the PS thin films via thermal annealing. A suite of, surface-sensitive techniques including atomic force microscopy, grazing incidence small-angle X-ray scattering, X-ray/neutron reflectivity, and sum frequency generation spectroscopy in conjunction with the established solvent leaching process enabled us to unveil the polymer chain conformation and the dispersion structure of the nanoparticles at the film substrate interface. The results evidenced that thermal annealing promotes irreversible polymer adsorption onto the substrate surface along with the migration of the nanoparticles. In addition, we found that the migration of the nanoparticles causes the changes in the conformations and interfacial orientations of the adsorbed polymer chains compared to those of the adsorbed polymer chains formed in the nanoparticle-free PS thin film. The resultant interfacial polymer structure allows for the interpenetration between free chains and the adsorbed chains, thereby stabilizing the thin film..
56. Toyoaki Hirata, Hisao Matsuno, Daisuke Kawaguchi, Manabu Inutsuka, Tomoyasu Hirai, Masaru Tanaka, Keiji Tanaka, Dynamics of a bioinert polymer in hydrated states by dielectric relaxation spectroscopy, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10.1039/c6cp07322k, 19, 2, 1389-1394, 2017.01, The chain dynamics of well-defined poly(2-methoxyethyl acrylate) (PMEA), which has been used in practice as a bioinert coating for heart-lung machines, was examined as a function of water content by dielectric relaxation spectroscopy (DRS). Two relaxation processes observed in both dried and hydrated films were assigned to the segmental motion (alpha-process) and the relatively smaller scale motion such as the hindered rotation of side chains (beta-process). Water molecules adsorbed on PMEA made the alpha-process faster, meaning that water molecules in PMEA played the role of a plasticizer. Combining the above knowledge with the depth dependence of water content in the PMEA film previously obtained by neutron reflectivity, the segmental dynamics of PMEA at the water interface, which should be crucial to bio-inertness, is discussed. We found that the segmental motion was markedly faster than that in the bulk and almost comparable to the side chain motion..
57. Atsuomi Shundo, Koichiro Hori, Yasuyuki Tezuka, Takuya Yamamoto, Keiji Tanaka, Load-Induced Frictional Transition at a Well-Defined Alkane Loop Surface, LANGMUIR, 10.1021/acs.langmuir.6b04042, 33, 9, 2396-2401, 2017.03, Self-assembled monolayers (SAMs) have attracted considerable attention as a tool to confer desirable properties on material surfaces. So far, molecules used for the SAM formation are generally limited to linear ones and thus chain ends dominate the surface properties. In this study, we have successfully demonstrated unique frictional properties of a SAM composed of alkane loops from cyclic alkanedisulfide on a gold substrate, where both sulfurs are bound to gold. The frictional response was proportional to the load. However, once the load went beyond a threshold value, the frictional response became more dominant. Such a frictional transition was reversible and repeatable and was not discerned for a corresponding SAM composed of n-alkyl chains. The load-induced change in the frictional response from the alkane loops could be associated with the conformational change of the alkane loops. The present results differ from most studies, in which the surface properties are designed on the basis of functional chain end groups..
58. Yukari Oda, Cui Zhang, Daisuke Kawaguchi, Hisao Matsuno, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Design of Blood-Compatible Interfaces with Poly(vinyl ether)s, ADVANCED MATERIALS INTERFACES, 10.1002/admi.201600034, 3, 12, 2016.06.
59. Yuma Morimitsu, Hisao Matsuno, Noboru Ohta, Hiroshi Sekiguchi, Keiji Tanaka, Direct Correlation between Molecular Cross-linking and Macroscopic Mechanical Properties for Green Solids of Deoxyribonucleic Acids, CHEMNANOMAT, 10.1002/cnma.201600222, 2, 11, 1023-1027, 2016.11, Double-stranded deoxyribonucleic acids (DNAs) were intermolecularly cross-linked using 2,5-hexanedione under reductive amination conditions in aqueous phase. Cross-linking points between DNAs were directly observed by atomic force microscopy in conjunction with a conventional gel electrophoresis analysis. While DNA chains near cross-linking points were denatured, DNA chains not near cross-linking points maintained B-form double strands. A transparent and self-supported film of cross-linked DNA (DNA-c) was obtained by a simple solvent-casting method. The tensile properties of DNA-c films were much better than those of non-cross-linked DNA (DNA-n) films due to the presence of the cross-linking portions. Structural analyses based on wide-angle X-ray diffraction measurements revealed that the reorientation of DNA-c was remarkably restricted by the introduction of cross-linking points..
60. Atsuomi Shundo, Koichiro Hori, David P. Penaloza, Yuji Matsumoto, Yasushi Okumura, Hirotsugu Kikuchi, Kyung Eun Lee, Sang Ouk Kim, Keiji Tanaka, Hierarchical spatial heterogeneity in liquid crystals composed of graphene oxides, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10.1039/c6cp03614g, 18, 32, 22399-22406, 2016.08, Graphene oxide (GO) is a class of two-dimensional materials with a thickness of about 1 nm and a broad distribution of lateral dimension commonly approaching several micrometers. A dispersion of GOs in water often forms a liquid crystal, which is expected to be a promising precursor for the fabrication of carbon-based materials with well-ordered structures. To accelerate the application of GO-based liquid crystals, their structures and physical properties at various sizes must be well understood. To that end, we examined the local rheological properties of GO-based liquid crystals in the nematic phase using a particle tracking technique, where local properties can be accessed by observing the thermal motion of embedded probe particles. Particle diffusion was spatially heterogeneous, and depended on the size of the particles. Such a size-dependent heterogeneity can be associated with a hierarchical local environment, which is time-dependent for this system. The anisotropic particle diffusion originated from particles trapped in between the GO layers and in isotropic-like regions. The aggregation states of the GO dispersion composed of nematic and isotropic-like regions were observed using confocal laser scanning microscopy..
61. Shinichiro Shimomura, Hisao Matsuno, Toshiyuki Ohta, Seiichi Kawahara, Keiji Tanaka, Initial Adhesion of Fibroblasts on Thin Rubber Scaffolds, CHEMISTRY LETTERS, 10.1246/cl.160061, 45, 4, 475-477, 2016.04, Cell adhesion behaviors on thin synthetic and natural rubbers supported on solid substrates were examined. When the film was thinner than 60 nm, the adhesion of L929 fibroblasts was clearly promoted. This can be explained in terms of the manifestation of mechanical response from the hard solid substrate. Protein-free natural rubber exhibited better performance than polyisoprene as a scaffold..
62. F. Chen, D. Peng, Y. Ogata, K. Tanaka, Z. Yang, Y. Fujii, N. L. Yamada, C. -H. Lam, O. K. C. Tsui, Confinement Effect on the Effective Viscosity of Plasticized Polymer Films, MACROMOLECULES, 10.1021/acs.macromol.5b01780, 48, 20, 7719-7726, 2015.10, We have measured the effective viscosity of polystyrene films with a small (4 wt %) added amount of dioctyl phthalate (DOP) deposited on silica. A broad range of molecular weights, M-w, from 13.7 to 2100 kg/mol was investigated. Our result shows that for the thin films with M-w < similar to 400 kg/mol the addition of DOP causes the effective viscosity to decrease by a factor of similar to 4, independent of M-w. But for the higher M-w, films, the effective viscosity of the DOP added films creeps toward that of the neat films with increasing M-w. A model assuming the effective viscosity to be dominated by enhanced surface mobility for the lower M-w films but surface-promoted interfacial slippage for the higher M-w films is able to account for the experimental observations..
63. Toyoaki Hirata, Hisao Matsuno, Daisuke Kawaguchi, Tomoyasu Hirai, Norifumi L. Yamada, Masaru Tanaka, Keiji Tanaka, Effect of Local Chain Dynamics on a Bioinert Interface, LANGMUIR, 10.1021/acs.langmuir.5b00258, 31, 12, 3661-3667, 2015.03, Although many kinds of synthetic polymers have been investigated to construct blood-compatible materials, only a few have achieved success. To establish molecular designs for blood-compatible polymers, the chain structure and dynamics at the water interface must be understood using solid evidence as the first bench mark. Here we show that polymer dynamics at the water interface impacts on structure of the interfacial water, resulting in a change in protein adsorption and of platelet adhesion. As a particular material, a blend composed of poly(2-methoxyethyl acrylate) (PMEA) and poly(methyl methacrylate) was used. PMEA was segregated to the water interface. While the local conformation of PMEA at the water interface was insensitive to its molecular weight, the local dynamics became faster with decreasing molecular weight, resulting in a disturbance of the network structure of waters at the interface. This leads to the extreme suppression of protein adsorption and platelet adhesion..
64. Ayanobu Horinouchi, Norifumi L. Yamada, Keiji Tanaka, Aggregation States of Polystyrene at Nonsolvent Interfaces, LANGMUIR, 10.1021/la500829p, 30, 22, 6565-6570, 2014.06, The aggregation states of polystyrene (PS) thin films at interfaces with nonsolvents such as water, methanol, and hexane were examined by specular neutron reflectivity and sum-frequency generation vibrational spectroscopy. The density profiles of the PS thin films along the direction normal to the interface with water and methanol were comparable to that in air. However, this was not the case for the film in hexane exhibiting a diffuse interfacial layer due to swelling. Also, the local conformation of PS in the outermost region of the films was quite sensitive to the surrounding environment and consequently responded to a change in its environment. This was the case for typical nonsolvents such as water and methanol. The extent of the conformational change might be explained in terms of the interfacial energy..
65. Takaaki Date, Yuko Ueda, Hironori Atarashi, Toshiki Sawada, Hideyo Matsuzawa, Keiji Tanaka, Takeshi Serizawa, Difference in Protein Adsorption Onto Polymer Films With or Without Thermal Annealing, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 10.1166/jnn.2014.8580, 14, 4, 3106-3111, 2014.04, Protein adsorptions onto non-annealed (NA) and thermally annealed (TA) polyetherimide films were examined by surface plasmon resonance measurements. Proteins adsorbed onto the NA films with smaller adsorption constants in comparison with the TA films. Neutron reflectivity measurements of the two films suggested that the outermost region of the NA films swelled with larger amounts of water molecules than the TA films. It is plausible that the aforementioned difference in the protein adsorption properties is derived from the difference in the interfacial aggregation structures of the two films..
66. Masayuki Haraguchi, Tomoyasu Hirai, Masaaki Ozawa, Katsuaki Miyaji, Keiji Tanaka, Hydrophobic acrylic hard coating by surface segregation of hyper-branched polymers, APPLIED SURFACE SCIENCE, 10.1016/j.apsusc.2012.11.160, 266, 235-238, 2013.02, The ability of hyperbranched polymers (HBPs) to preferentially segregate to the surface of its matrix owing to its unique structure makes it a good candidate as a surface modifier. One particular challenge in its application as an efficient surface modifier, however, is its possible elimination from the surface due to the lack of attachments between a HBP (modifier) and its host material (polymer matrix). Here, we present a novel approach to efficiently prevent the removal of HBPs from the surface of its host material by directly reacting a HBP containing fluoroalkyl segments (F-HBP) to a multi-functional acrylate monomer prior to curing. We also have characterized surface structure and wettability of the acrylic hard coating material by X-ray photoelectron spectroscopic and contact angle measurements, respectively. The results show that since F-HBP was segregated at the surface, the surface became hydrophobic and more stable. Thus, we claim that our approach results in the formation of a water-repellent acrylic hard coating material. (C) 2012 Elsevier B.V. All rights reserved..
67. Atsuomi Shundo, Koichiro Hori, David P. Penaloza Jr., Keiji Tanaka, Optical tweezers with fluorescence detection for temperature-dependent microrheological measurements, Review of Scientific Instruments, 10.1063/1.4789429, 84, 1, 2013.01, We introduce a setup of optical tweezers, capable of carrying out temperature-dependent rheological measurements of soft materials. In our setup, the particle displacement is detected by imaging a bright spot due to fluorescence emitted from a dye-labeled particle against a dark background onto a quadrant photodiode. This setup has a relatively wide space around the sample that allows us to further accessorize the optical tweezers by a temperature control unit. The applicability of the setup was examined on the basis of the rheological measurements using a typical viscoelastic system, namely a worm-like micelle solution. The temperature and frequency dependences of the local viscoelastic functions of the worm-like micelle solution obtained by this setup were in good accordance with those obtained by a conventional oscillatory rheometer, confirming the capability of the optical tweezers as a tool for the local rheological measurements of soft materials. Since the optical tweezers measurements only require a tiny amount of sample (∼40 μL), the rheological measurements using our setup should be useful for soft materials of which the available amount is limited. © 2013 American Institute of Physics..
68. Ayanobu Horinouchi, Hironori Atarashi, Yoshihisa Fujii, Keiji Tanaka, Dynamics of Water-Induced Surface Reorganization in Poly(methyl methacrylate) Films, MACROMOLECULES, 10.1021/ma3002559, 45, 11, 4638-4642, 2012.06, At the outermost surface, aggregation states of polymers generally tend to alter to their most stable ones in response to their surrounding environment. We here apply a time-resolved contact angle measurement to study the rate of the surface reorganization of poly(methyl methacrylate) (PMMA) in water. By doing these measurements at various temperatures, it is possible to determine the apparent activation energy of the surface dynamics based on the relation of the surface relaxation time and temperature. Also, the sum-frequency generation spectroscopy revealed that the surface reorganization involves the conformational changes in the main chain part as well as the side chains. Hence, the dynamics observed here may reflect the segmental motion at the outermost region of the PMMA film, in which water plays as a plasticizer..
69. Masayuki Haraguchi, Tomoyasu Hirai, Masahiro Ozawa, Misao Miyamoto, Keiji Tanaka, One-step Synthesis of Hyper-branched Polymer with Perfluoroalkyl Segments, KGK-KAUTSCHUK GUMMI KUNSTSTOFFE, 65, 7-8, 34-38, 2012.07, Initiator-fragment incorporation radical polymerization (IFIRP) of commercially available fluorinated monomers was performed in the presence of cross-linking agents, resulting in a hyperbranched polymer with perfluoroalkyl groups (F-HBP). In our one-step method, a F-HBP was successfully prepared without gelation within 1 h. The F-HBP exhibited interesting properties based on both the hyperbranched architecture and the perfluoroalkyl groups, such as good solubility in common organic solvents, high thermal stability, and low surface free energy..
70. Tomoyasu Hirai, Liu Huan, Yoshihiro Ohta, Tsutomu Yokozawa, Keiji Tanaka, Surface Segregation of Well-defied N-Substituted Hyperbranched Polyamides in Linear Polymer Matrix, CHEMISTRY LETTERS, 10.1246/cl.2011.366, 40, 4, 366-367, 2011.04, Surface segregation of well-defined N-substituted hyperbranched polyamides (HBPA) with various side chain lengths in linear polystyrene matrix was studied. To what extent HBPA was segregated at the surface was dependent on the side chain length, which regulated intermolecular interactions among HBPA molecules via steric hindrance..
71. Naokazu Idota, Kenichi Nagase, Keiji Tanaka, Teruo Okano, Masahiko Annaka, Stereoregulation of Thermoresponsive Polymer Brushes by Surface-Initiated Living Radical Polymerization and the Effect of Tacticity on Surface Wettability, LANGMUIR, 10.1021/la1024229, 26, 23, 17781-17784, 2010.12, In this study, stereocontrolled poly(N-isopropylacrylamide) (PIPAAm) brushes were grafted from surfaces by atom transfer radical polymerization (ATRP) in the presence of a Lewis acid, and the effect of PIPAAm brash tacticity on the thermoresponsive wettabiliy was investigated. PIPAAm grafted by ATRP in the presence of Y(OTf)(3) showed high isotacticity, while the control brush polymerized in the absence of Y(OTf)(3) was clearly atactic. The isotacticity and molecular weight of PIPAAm brushes were controlled by polymerization conditions. The wettability of isotactic PIPAAm-grafted surfaces decreased slightly below 10 degrees C, although the phase transition temperature of atactic surface was 30 degrees C, and the bulk isotactic polymer was water-insoluble between 5 and 45 degrees C..
72. Ayanobu Horinouchi, Yoshihisa Fujii, Norifumi L. Yamada, Keiji Tanaka, Surface Reorganization of Thin Poly(methyl methacrylate) Films Induced by Water, CHEMISTRY LETTERS, 10.1246/cl.2010.810, 39, 8, 810-811, 2010.08, Neutron reflectivity revealed that the surface aggregation states of poly(methyl methacrylate) film can be altered by water, which is a typical nonsolvent, in a relatively large scale..
73. Yoshihisa Fujii, Hironori Atarashi, Masahiro Hino, Toshihiko Nagamura, Keiji Tanaka, Interfacial Width in Polymer Bilayer Films Prepared by Double-Spin-Coating and Flotation Methods, ACS APPLIED MATERIALS & INTERFACES, 10.1021/am9004336, 1, 9, 1856-1859, 2009.09, A spin-coating method with the aid of selective solvents has been used to construct m,u. Itilayer struct ures for organic devices under the assumption that the solvents do not invade, a preformed structure. To confirm the assumption, we examined the interfacial width (lambda(i)) of model polymer bilayers, composed of polystyrene and perdeuterated poly(methyl methacrylate), prepared by spin-coating and notation methods. Neutron reflectivity measurements revealed that the lambda(i) value was,larger for the spin-coating method than for the flotation method. These results cast doubt on the validity of the assumption. This knowledge should be kept in mind when this method is applied to construct multilayer structures..
74. Naoki Sato, Yamamoto Takeshi, Iwasaki Yuki, Kato Koji, Yoshikawa Masatomo, Hirasawa Yasuhiro, Kamiya Masataka, Murai Koji, Takano Teruo, Tanaka Keiji, Important factors for the prevention of renal function under the inhibition of rennin-angiotensin-aldosterone system in acute heart failure, JOURNAL OF CARDIAC FAILURE, 10.1016/j.cardfail.2006.08.171, 12, 8, S179-S179, 2006.10.
75. Keiji Tanaka, Photo-induced phenomena in chalcogenide glass: Comparison with those in oxide glass and polymer, JOURNAL OF NON-CRYSTALLINE SOLIDS, 10.1016/j.jnoncrysol.2006.02.070, 352, 23-25, 2580-2584, 2006.07, Two topics, the both being related with localized states in non-crystalline solids, are studied. One is a comparison of photo-induced phenomena in oxide, chalcogenide, and organic materials. Despite of different inorganic and organic structures, there exist many similarities in photo-induced phenomena, which can be ascribed to excitation of localized electronic states. The other topic concerns photo-induced phenomena induced by linear and non-linear excitation. A result on As2S3 demonstrates that band-gap excitation by one- and two-photon processes provides different changes. It is suggested that the two-photon process occurs resonantly at around localized states in amorphous materials, and the process plays important roles in the structural change. (c) 2006 Elsevier B.V. All rights reserved..
76. H Yakabe, K Tanaka, T Nagamura, S Sasaki, O Sakata, A Takahara, T Kajiyama, Grazing incidence X-ray diffraction study on surface crystal structure of polyethylene thin films, POLYMER BULLETIN, 10.1007/s00289-004-0329-2, 53, 3, 213-222, 2005.01, Crystal structure in thin films of melt-crystallized and annealed polyethylene (PE) was examined by grazing incidence X-ray diffraction measurements. Choosing appropriate incident angles of X-rays to the films, surface and bulk molecular aggregation states were successfully extracted. Consequently, it was found that chain packing structure in the surface region was different from that in the bulk one. Based on paracrystalline analysis for the (110) reflection and its higher-order ones of PE orthorhombic crystal, it was clarified that the ordering for the crystalline lattice was lower in the surface region. Also, apparent crystallinity in the surface was lower than the bulk one. These results indicate that disordered crystallites were preferentially formed in the surface region..
77. Keiji Tanaka, Shiyu Dai, Tisato Kajiyama, Keigo Aoi, Masahiko Okada, Aggregation states and molecular motion in amphiphilic poly(amido amine) dendrimer monolayers on solid substrates, Langmuir, 10.1021/la0261592, 19, 4, 1196-1202, 2003.02, Monolayers of third-generation amphiphilic poly(amido amine) (PAMAM) dendrimer were prepared at the air/water interface and then were successfully transferred onto silicon wafers by a horizontal lifting method. A comprehensive characterization of the PAMAM monolayers was made, structurally and dynamically, by scanning force microscopy in conjunction with X-ray reflectivity and X-ray photoelectron spectroscopy. The PAMAM molecules sit on the substrate with an oblate shape, in which hydrophilic core and hydrophobic alkyl end groups were toward substrate and air sides, respectively. In the PAMAM monolayers, distinct three, αa-, αH(2)O- and δ-, relaxation processes were observed on lateral force-temperature curves. They were assigned to segmental motion, plasticized segmental motion by residual water molecules, and a local mode relaxation, respectively..
78. K. Tanaka, M. Tanaka, Simulation of an aperture in the thick metallic screen that gives high intensity and small spot size using surface plasmon polariton, Journal of Microscopy, 10.1046/j.1365-2818.2003.01155.x, 210, 3, 294-300, 2003.06, The optical wave behaviour around a subwavelength aperture in a thick metallic screen is examined through three-dimensional computer simulation. Treating the metallic screen as a dielectric slab with complex-valued permittivity, it is possible to design an aperture that simultaneously provides high intensity and small spot size through the excitation of surface plasmon polaritons on the side walls of the aperture..
79. T Kajiyama, D Kawaguchi, K Tanaka, Surface mobility in monodisperse polystyrene films, MACROMOLECULAR SYMPOSIA, 10.1002/masy.200351111, 201, 95-102, 2003.09, Surface dynamics in monodisperse polystyrene films was examined by lateral force microscopy in conjunction with dynamic secondary ion mass spectroscopy. Glass transition temperature, T-g, at the surface was markedly lower than the corresponding bulk T-g. Also, it was shown that polymer chains present at the surface could diffuse even at a temperature below the bulk T-g. The surface depth, in which molecular motion was activated, was of the order of 5 nm..
80. FC Xie, HF Zhang, FK Lee, BY Du, OKC Tsui, Y Yokoe, K Tanaka, A Takahara, T Kajiyama, TB He, Effect of low surface energy chain ends on the glass transition temperature of polymer thin films, MACROMOLECULES, 10.1021/ma011689a, 35, 5, 1491-1492, 2002.02.
81. HQ Xiang, K Tanaka, T Kajiyama, Gas-sensing properties of dilithium octacyanophthalocyanine Langmuir-Blodgett films, LANGMUIR, 10.1021/la026161t, 18, 23, 9102-9105, 2002.11.
82. Keiji Tanaka, Hyuk Yu, Lipase activity on lipid/polymer binary monolayers: Lateral diffusion-controlled enzyme kinetics, Langmuir, 10.1021/la010965b, 18, 3, 797-804, 2002.02, This is a follow-up study to our recent reports of lipase catalysis on uniphasic binary monolayers of L-α-dilauroylphosphatidylcholine (DLPC) and cholesterol. The earlier studies were undertaken to show that the reaction kinetics on monolayers of ester hydrolysis catalyzed by an interface active enzyme, lipase, is closely correlated to the lateral dynamics, i.e., the hydrolysis of a lipase substrate is a diffusion-controlled process, whereby the rates were quantitatively analyzed in terms of a theory of purely two-dimensional diffusion-controlled reactions. In so establishing, cholesterol was used as the second component to retard the lateral diffusion coefficient of DLPC to different extents. On the other hand, phospholipids and cholesterol are being found to form "condensed complexes" even in homogeneous monolayers, hence the finding of the diffusion-controlled processes might well be construed to be unique to the phospholipid-cholesterol system. To show that the diffusion-controlled reaction kinetics on monolayers is of more general validity, i.e., not system-specific, we chose a completely different second component to constitute a binary homogeneous monolayer system by which we can vary the lipid diffusion coefficient. The second component is a synthetic polymer, poly(tert-butyl methacrylate) (PtBMA), well-known for its surface activity on the air/water interface, and is demonstrated to form uniphasic monolayers with DLPC at the air/aqueous buffer (pH 7) interface. Upon completing the entire set of measurements for the diffusion coefficients and the hydrolysis rates with the same substrate, umbelliferone stearate, we reached the conclusions that what we found with DLPC/ cholesterol are not unique to the system but equally applicable to DLPC/PtBMA, whereas the polymer is not likely to exert the same sort of retardation effect on monolayer dynamics by specific interactions that result in condensed complexes of phospholipid and cholesterol..
83. XQ Jiang, K Tanaka, A Sakai, A Takahara, T Kajiyama, Surface relaxation behavior of proton- and perfluoroalkyl-terminated poly(2-vinylpyridine) films, POLYMER, 42, 21, 8959-8964, 2001.10, Proton- and perfluoroalkyl-terminated poly(2-vinylpyridine) (P2VP-H and P2VP-C2C8F) were anionically synthesized. Surface molecular motions of P2VP-H and P2VP-C2C8F films prepared on hydrophilic silicon wafers were examined by lateral force microscopy (LFM). Surface glass transition temperature, T-g(s), of P2VP-C2C8F was lower than that of P2VP-H probably due to the difference of the surface concentration of chain ends. Also, both T-g(s) values were lower than each corresponding bulk glass transition temperature, T-g(s). Surface molecular motion in an ultrathin film was less activated than that of the thick film, although Tin the ultrathin film remained lower than T-g(b). In the case of ultrathin films, the surface/interface area to volume ratio becomes larger, and thus the thermal molecular motion at the surface is affected by that at the polymer/substrate interface. Since molecular mobility on the substrate might be restricted owing to the polar attractive interaction between polymer segments and the hydrophilic substrate, the activation of surface molecular motion apparently turns weak for such an ultrathin film. (C) 2001 Elsevier Science Ltd. All rights reserved..
84. T Kajiyama, K Tanaka, N Satomi, A Takahara, Surface rheology of polymeric solids, CHINESE JOURNAL OF POLYMER SCIENCE, 18, 3, 239-248, 2000.05, Surface molecular motions of amorphous polymeric solids have been directly measured on the basis of scanning viscoelasticity microscopic (SVM) and lateral force microscopic (LFM) measurements. SVM and LFM measurements were carried out fur films of conventional monodisperse polystyrene (PS) with sec-butyl] and proton-terminated end groups at room temperature, In the case of the number-average molecular weight, M-n, less than ca. 4.0 x 10(4), the surface was in a glass-rubber transition state even though the bulk glass transition temperature, T-g was far above room temperature, meaning that the surface molecular motion was fairly active compared with that in the bulk. LFM measurements of the monodisperse PS films at various scanning rates and temperatures revealed that the time-temperature superposition was applicable to the surface mechanical relaxation behavior and also that the surface glass transition temperature, T-g(sigma) was depressed in comparison with the bulk one even though the magnitude of M-n was fairly high at 1.40 x 10(5). The surface molecular motion of monodisperse PS with various chain end groups was investigated on the basis of temperature-dependent scanning viscoelasticity microscopy (TDSVM). The T(g)(sigma)s for the PS films with M-n of 4.9 x 10(3) to 1.45 x 10(6) measured by TDSVM were smaller than those for the bulk one, with corresponding M(n)s, and the T(g)(sigma)s for M(n)s smaller than ca. 4.0 x 104 were lower than room temperature (293 K), The active thermal molecular motion at the polymeric solid surface can be interpreted in terms of an excess free volume near the surface region induced by the surface localization of chain end groups. In the case of M-n = ca. 5.0 x 10(4), the T(g)(sigma)s for the alpha,omega-diamino-terminated PS (alpha,omega-PS(NH2)(2)) and alpha,omega-dicarboxy-terminated PS (alpha,omega-PS(COOH)(2)) films were higher than that of the PS film. The change of T(g)(sigma)s for the PS film with various chain end groups can be explained in terms of the depth distribution of chain end groups at the surface region depending on the relative hydrophobicity..
85. M. Tanaka, K. Tanaka, On a new boundary element solution scheme for elastoplasticity, Ingenieur-Archiv, 10.1007/BF00778424, 50, 5, 289-295, 1981.09, A new boundary element discretization scheme is proposed for three-dimensional elastoplasticity. The governing equation of the problem is transformed into a set of integral equations in the domain and on the boundary. The resulting integral equations are discretized by means of boundary elements as well as volume elements. The system of linear equations thus obtained is solved simultaneously. The formulation is made in terms of increments and also Green's functions available in the literature for elastostatics. Since the domain is also discretized into volume elements in the proposed solution scheme, the incremental solutions at every loading step can be obtained without any iterative procedure. © 1981 Springer-Verlag..
86. Kentaro Yamamoto, Daisuke Kawaguchi, Tatsuki Abe, Takeshi Komino, Masashi Mamada, Taizo Kabe, Chihaya Adachi, Kensuke Naka, and Keiji Tanaka, Surface Segregation of a Star-Shaped Polyhedral Oligomeric Silsesquioxane in a Polymer Matrix, Langmuir, doi.org/10.1021/acs.langmuir.0c01785, 36, 33, 9960-9966, 2020.07.
87. Mika Aoki, Atsuomi Shundo, Satoru Yamamoto, Keiji Tanaka, Effect of a Heterogeneous Network on Glass Transition Dynamics and Solvent Crack Behavior of Epoxy Resins, Soft Matter, 10.1039/d0sm00625d, 16, 32, 7470-7478, 2020.07.
88. Shin Sugimoto, Manabu Inutsuka, Daisuke Kawaguchi, Keiji Tanaka, The Effect of Interfacial Dynamics on the Bulk Mechanical Properties of Rubber Composites, Polymer Journal, 10.1038/s41428-019-0254-8, 52, 217-223, 2019.08.
89. Hisao Matsuno, Masayasu Totani, Arisa Yamamoto, Masayuki Haraguchi, Masaaki Ozawa, Keiji Tanaka, Water-Induced Surface Reorganization of Bioscaffolds Composed of an Amphiphilic Hyperbranched Polymer, Polymer Journal, 10.1038/s41428-019-0212-5, 51, 10, 1045-1053, 2019.10, The ability to freely control the surface of bioscaffolds in a water environment is desirable to regulate cellular behaviors in vitro. Herein, we study the surface aggregation states of scaffold films composed of a multifunctional hyperbranched polymer (HBP) with perfluorohexylethyl, carboxy, and cyano groups that was prepared using a spin-coating method. Static contact angle measurements in conjunction with X-ray photoelectron spectroscopy revealed that perfluorohexylethyl groups were segregated at the surface of the HBP film in air, and these findings were more remarkable for the film treated with thermal annealing. Once the HBP film contacted water, HBP chains reorganized at the surface to minimize the free energy, resulting in the formation of a relatively hydrophilic surface. This surface reorganization was discernably faster and more remarkable for the non-annealed HBP film than for the annealed film. As fundamental characteristics of a cellular scaffold, protein adsorption, in addition to the initial adhesion and proliferation of fibroblasts, was examined using microscopy. The amount of fibronectin adsorbed depended on the presence of thermal annealing during the scaffold preparation process. A relatively larger amount of fibronectin adsorbed to the non-annealed HBP film promoted the initial adhesion and subsequent proliferation of fibroblasts..
90. Atsuomi Shundo,Yuji Matsumoto,Hisato Hayashi,Nobutomo Tsuruzoe,Hisao Matsuno,Keiji Tanaka , Mesoscopic Heterogeneity in a Nanocellulose-Containing Cell Storage Medium, Journal of Materials Chemistry B, 10.1039/d0tb00219d, 2020.04.
91. Hung K. Nguyen, Daisuke Kawaguchi, Keiji Tanaka, Effect of Molecular Architecture on Conformational Relaxation of Polymer Chains at Interfaces, Macromolcular Rapid Communication, 10.1002/marc.202000096, 2020.05.
92. Kazuo Sakurai, Mikihito Takenaka, Keiji Tanaka, Special issue
Cutting Edge of Scattering from Softmaterials, Polymer Journal, 10.1038/s41428-018-0154-3, 51, 2, 2019.02.
93. Keiji Tanaka, PJ ZEON award for outstanding papers in Polymer Journal 2018, Polymer Journal, 10.1038/s41428-019-0188-1, 51, 6, 531-533, 2019.01.
94. Yuma Morimitsu, Daniel Salatto, Naisheng Jiang, Mani Sen, Shotaro Nishitsuji, Benjamin M. Yavitt, Maya K. Endoh, Ashwanth Subramanian, Chang Yong Nam, Ruipeng Li, Masafumi Fukuto, Yugang Zhang, Lutz Wiegart, Andrei Fluerasu, Keiji Tanaka, Tadanori Koga, "Structurally Neutral" Densely Packed Homopolymer-Adsorbed Chains for Directed Self-Assembly of Block Copolymer Thin Films, Macromolecules, 10.1021/acs.macromol.9b00597, 52, 14, 5157-5167, 2019.07, We here report that adsorbed chains composed of one of the constituent blocks can be used as a new surface modification approach to induce perpendicularly oriented lamellar microdomains in block copolymer thin films. A nearly symmetric polystyrene-block-poly(methyl methacrylate) (PS-block-PMMA) diblock copolymer was used as a model. Densely packed PS- or PMMA-adsorbed chains of about 2-3 nm in thickness ("polymer nanocoatings") were deposited on silicon (Si) substrates using a solvent-rinsing approach. Spin-cast films of 40 or 60 nm-thick PS-block-PMMA (equivalent to two or three interdomain spacings) were subsequently deposited onto the PS or PMMA nanocoatings. Grazing incidence small-angle X-ray scattering experiments revealed the formation of perpendicularly oriented lamellar microdomains within the entire films at 200 °C, where balanced interfacial interactions at the polymer-air interface were achieved. Additionally, X-ray photon correlation spectroscopy studies demonstrated the dynamics of the fully standing lamellar microdomains in the melt, which are coupled to cooperative interdomain movement. We demonstrate that the "neutrality" of the nanocoating is attributed to its noninteractive property against both blocks. This "structurally neutral" property prevents adsorption of the PS-block-PMMA chains on the bare Si substrate that causes the undesirable substrate field effect..
95. Hung K. Nguyen, Shin Sugimoto, Asuka Konomi, Manabu Inutsuka, Daisuke Kawaguchi, Keiji Tanaka, Dynamics Gradient of Polymer Chains near a Solid Interface, ACS Macro Letters, 10.1021/acsmacrolett.9b00351, 8, 8, 1006-1011, 2019.08, 石英界面におけるポリイソプレン鎖およびニトリルゴム鎖の緩和ダイナミクスをエバネッセント波励起蛍光偏光解消法、誘電緩和測定および和周波発生分光測定に基づき、界面からの距離の関数として評価した。その結果、界面層には分子鎖ダイナミクスの勾配が存在することを明らかにし、それが弱く吸着した鎖と強く吸着した鎖によるものと説明した。強く吸着した鎖の緩和はバルクのそれと比較して10桁以上遅くなることを示している。.
96. Aggregation state and thermal molecular motion of a bio-inert polymer at the water interface.
97. Biao Zuo, Quanyin Xu, Tiancheng Jin, Huimin Xing, Jiacheng Shi, Zhiwei Hao, Li Zhang, Keiji Tanaka, Xinping Wang, Suppressed Surface Reorganization in a High-Density Poly(methyl methacrylate) Brush, Langmuir, 10.1021/acs.langmuir.9b02581, 35, 46, 14890-14895, 2019.11, A high-density poly(methyl methacrylate) (PMMA) brush (σ = 0.77 chain/nm2) with a lower molecular weight distribution was prepared onto a silicon wafer by surface-initiated atom transfer radical polymerization. The surface of the PMMA brush chains was characterized upon the process of the environmental change, from air to water, using contact angle measurements in conjunction with sum-frequency generation spectroscopy. The surface structure and properties altered less with the changing environment from air to water for the PMMA brush than for a spin-coated film; that is, the extent of surface reorganization could be suppressed by grafting densely-packed chains onto a substrate. Also, the water penetration into the brush surface was inhibited because of the densely packed chain structure..
98. Maya K. Endoh, Yuma Morimitsu, Daniel Salatto, Zhixing Huang, Mani Sen, Weiyi Li, Yizhi Meng, David G. Thanassi, Jan Michael Y. Carrillo, Bobby G. Sumpter, Daisuke Kawaguchi, Keiji Tanaka, Tadanori Koga, Protein Resistance Driven by Polymer Nanoarchitecture, ACS Macro Letters, 10.1021/acsmacrolett.9b00518, 8, 9, 1153-1159, 2019.09, We report that the nanometer-scale architecture of polymer chains plays a crucial role in its protein resistant property over surface chemistry. Protein-repellent (noncharged), few nanometer thick polymer layers were designed with homopolymer chains physisorbed on solids. We evaluated the antifouling property of the hydrophilic or hydrophobic adsorbed homopolymer chains against bovine serum albumin in water. Molecular dynamics simulations along with sum frequency generation spectroscopy data revealed the self-organized nanoarchitecture of the adsorbed chains composed of inner nematic-like ordered segments and outer brush-like segments across homopolymer systems with different interactions among a polymer, substrate, and interfacial water. We propose that this structure acts as a dual barrier against protein adsorption..
99. Tsukasa Miyazaki, Noboru Miyata, Mitsunori Asada, Yoshihiro Tsumura, Naoya Torikai, Hiroyuki Aoki, Katsuhiro Yamamoto, Toshiji Kanaya, Daisuke Kawaguchi, Keiji Tanaka, Elucidation of a Heterogeneous Layered Structure in the Thickness Direction of Poly(vinyl alcohol) Films with Solvent Vapor-Induced Swelling, Langmuir, 10.1021/acs.langmuir.9b01665, 35, 34, 11099-11107, 2019.08, We investigated the swelling behaviors of poly(vinyl alcohol) (PVA) films deposited on Si wafers with water vapor, which is a good solvent for PVA for elucidating structural and dynamical heterogeneities in the film thickness direction. Using deuterated water vapor, structural and dynamical differences in the thickness direction can be detected easily as different degrees of swelling in the thickness direction by neutron reflectivity. Consequently, the PVA film with a degree of saponification exceeding 98 mol % exhibits a three-layered structure in the thickness direction. It is considered that an adsorption layer consisting of molecular chains that are strongly adsorbed onto the solid substrate is formed at the interface with the substrate, which is not swollen with water vapor compared with the bulk-like layer above it. The adsorption layer is considered to exhibit significantly slower dynamics than the bulk. Furthermore, a surface layer that swells excessively compared with the underneath bulk-like layer is found. This excess swelling of the surface layer may be related to a higher mobility of the molecular chains or lower crystallinity at the surface region compared to the underneath bulk-like layer. Meanwhile, for the PVA film with a much lower degree of saponification, a thin layer with a slightly lower degree of swelling than the bulk-like layer above it can be detected at the interface between the film and substrate only under a high humidity condition. This layer is considered to be the adsorption layer composed of molecular chains loosely adsorbed onto the Si substrate..
100. Yuji Matsumoto, Atsuomi Shundo, Hisato Hayashi, Nobutomo Tsuruzoe, Keiji Tanaka, Effect of the Heterogeneous Structure on Mechanical Properties for a Nanocellulose-Reinforced Polymer Composite, Macromolecules, 10.1021/acs.macromol.9b01866, 2019.01, Nanocellulose (NC), which consists of a bundled structure of cellulose chains, is a class of shape-anisotropic materials with a diameter of several tens of nanometers and a length of over several hundreds of nanometers. Because the production of NC is based on the extraction process from natural resources in water, NC is generally obtained in an aqueous dispersion state. Thus, an aqueous dispersion of NC can be regarded as a precursor for NC-reinforced polymer composites. The objective of this study is to gain a better understanding of (1) local rheological properties of the NC aqueous dispersion at various length scales using a particle tracking measurement and (2) how they affect the mechanical properties of the resultant NC-reinforced polymer composite. The observation of individual particles at different positions revealed that the NC aqueous dispersion was spatially heterogeneous at the characteristic length of a few tens of micrometers. When the NC aqueous dispersion was sonicated and subsequently left undisturbed at room temperature, the length scale of the heterogeneity decreased. From the NC aqueous dispersion with and without the sonication treatment, having smaller and larger length scale of heterogeneity, respectively, poly(vinyl alcohol) (PVA) films containing NC were fabricated. The dispersion state of NC in the PVA matrix was improved by the prior sonication treatment. The addition of NC remarkably enhanced the ductility of the PVA film. However, this was the case only after the sonication treatment. The knowledge here obtained should provide a novel concept for polymer composites with tunable mechanical properties, based on the precursor-based design..
101. Nozomi Itagaki, Daisuke Kawaguchi, Yukari Oda, Fumiya Nemoto, Norifumi L. Yamada, Tetsuo Yamaguchi, Keiji Tanaka, Surface Effect on Frictional Properties for Thin Hydrogel Films of Poly(vinyl ether), Macromolecules, 10.1021/acs.macromol.9b01786, 2019.01, Frictional properties play a key role in the performance of hydrogels in applications such as soft contact lenses, cell sheets, artificial articular cartilage, etc. Here we characterize the swollen state and frictional properties of thin hydrogel films composed of poly(2-methoxyethyl vinyl ether) on a nanometer scale using neutron reflectivity (NR) in conjunction with lateral force microscopy, leading to the discussion about the extent to which surface chains impact the frictional properties of gels. NR measurement revealed that the density profile for the hydrogel films in the interfacial region with water along the direction normal to the interface was well described by a parabolic function, which was generally used for swollen polymer brushes in a liquid. Lateral, or frictional, force (FL) first increased with increasing normal force (FN) and then reached a region where the dependence of FL on FN was extremely subtle. That is, there exist two regimes, I and II, for the relationship between FN and FL. The thickness of the interfacial layer composed of dangling chains, which should behave like brush chains, as determined by NR measurement, was in good accordance with the depth at which the regime transited from region I to II. The frictional properties of the thin hydrogel films could be better understood by considering the two contributions from the interfacial layer and the internal bulk region..
102. Mika Aoki, Atsuomi Shundo, Kenji Okamoto, Tatsuya Ganbe, Keiji Tanaka, Segregation of an Amine Component in a Model Epoxy Resin at a Copper Interface, Polymer Journal, 10.1038/s41428-018-0129-4, 51, 3, 359-363, 2019.03, Epoxy resins, which are obtained by the curing reaction of epoxy- and amine-compounds mixture, have been often utilized in contact with metals. We herein report on the chemical composition of the epoxy resin in close proximity to the copper interface on the basis of a non-destructive method. The concentration of the amine component in the interfacial region was 2-fold higher than that in the bulk, and the interfacial enrichment extended over at least 10 nm. [Figure not available: see fulltext.]..
103. Masayasu Totani, Ling Liu, Hisao Matsuno, Keiji Tanaka, Design of a Star-like Hyperbranched Polymer Having Hydrophilic Arms for Anti-biofouling Coating, Journal of Materials Chemistry B, 10.1039/c8tb03104e, 7, 7, 1045-1049, 2019.01, A star-like hyperbranched polymer having hydrophilic poly(ethyleneoxide acrylate) arms (HB-PEO9A) was prepared by a core-first method based on atom transfer radical polymerization. The PEO9A layer coated on a solid substrate was dissolved by water, and effectively inhibited protein adsorption and cell adhesion..
104. Shinichiro Shimomura, Hisao Matsuno, Yohei Kinoshita, Satoshi Fujimura, Keiji Tanaka, Cellular Behaviors on Polymeric Scaffolds with 2D-patterned Mechanical Properties, Polymer Journal, 10.1038/s41428-018-0043-9, 50, 8, 737-743, 2018.08, We propose a novel concept for cellular scaffolds with 2D-patterned mechanical properties. Thin films of glassy polystyrene (PS) with thicknesses ranging from 100 nm to 1 μm were prepared on epoxy resin-based line and space (L&S) patterned substrates. Although the outermost surface of PS on the L- and S-regions was sufficiently flat at the same level, the mechanical responses differed depending on the presence of the underlying resin foundation. The initial cell adhesion and spreading and the proliferation on the scaffolds were affected by the 2D-patterned mechanical properties, that is, cellular behavior was suppressed on mechanically unstable S-regions..
105. Keiji Tanaka, Hyitk Yu, Polymer modulated, diffusion-controlled enzyme kinetics on monolayers, Quaternary International, 41, 2, 1809-1810, 2000.08, A study was carried out to examine the monolayer dynamics and the hydrolysis kinetics of umbelliferone stearate (UMB-C18) on binary monolayers composed of dilauroylphosphatidylcholine (DLPC) and another viscosifier, PtBMA. Results of this study were compared to previous results using a different viscosifier, cholesterol, of the lipid monolayer..
106. Keiji Tanaka, Steven P. Mecca, Hyuk Yu, Lipase catalysis on monolayers at the air/water interface. 2. Diffusion-controlled kinetics on quasi-two-dimension, Langmuir, 10.1021/la990925w, 16, 6, 2672-2676, 2000.03, Homogeneous exoplasmic leaflets of biomembrane are mimicked by lipid monolayers at the air/water interface. The reaction rates of lipase (Pseudomonas cepacia) catalyzed hydrolysis of a substrate (umbelliferone stearate) on L-α-dilauroylphosphatidylcholine/cholesterol mixed monolayers at the air/water interface are examined as a function of cholesterol composition, which is to vary the dynamics of the system. Lateral mobility as a measure of dynamics of phospholipids and adsorbed lipase molecules are probed with the technique of fluorescence recovery after photobleaching. Upon correlating the lateral diffusion coefficients of a probe lipid and lipase with the interfacial hydrolysis kinetics, we show for the first time that the catalytic reactions on the monolayers are diffusion-controlled. Moreover, our results are in a quantitative agreement with the two-dimensional reaction dynamics theory of Torney and McConnell..
107. Keiji Tanaka, Patricia A. Manning, Hyuk Yu, Lipase catalysis on monolayers at the air/water interface. 1. Kinetic rate constants on quasi-two-dimension, Langmuir, 10.1021/la9909244, 16, 6, 2665-2671, 2000.03, Chemical reactions on a cell membrane surface are of pivotal importance for cellular functions such as intracellular signal transduction. Of the variety of membrane proteins, those imbedded in hemi-leaflets of bilayer membranes can be mimicked structurally and dynamically on monomolecular layers of phospholipids at the air/water interface. This is to report the kinetics of lipase (Pseudomonas cepacia) catalyzed hydrolysis of a substrate (umbelliferone stearate) on uniphasic L-α-dilauroylphosphatidylcholine monolayers at the air/water interface. A novel experimental protocol of the interfacial reaction is employed to probe the enzymatic kinetics. The kinetic rate constants on the monolayers are extracted from the substrate and the enzyme concentration dependences of the initial hydrolysis rate. The lipase on monolayers at the air/water interface is highly activated over that in bulk solution, and the turnover number of the lipase catalysis is strongly dependent on the surface pressure of monolayers..
108. T. Kajiyama, Keiji Tanaka, N. Satomi, Atsushi Takahara, Surface glass transition temperatures of monodisperse polystyrene films by scanning force microscopy, Science and Technology of Advanced Materials, 10.1016/S1468-6996(99)00005-4, 1, 1, 31-35, 2000.03, Surface molecular motion of monodisperse polystyrene (PS) films was examined by scanning viscoelasticity microscopy (SVM) in conjunction with lateral force microscopy (LFM). The dynamic storage modulus, E1, and loss tangent, tan δ, at a PS film surface with a smaller number-average molecular weight, Mn, than 40k were found to be smaller and larger than those for the bulk sample even at room temperature, meaning that the PS surface is in a glass-rubber transition state or a fully rubbery one at this temperature if the Mn, is small. In order to elucidate quantitatively how vigorous the molecular motion at the PS surface is, SVM and LFM measurements were made at various temperatures. The glass transition temperature, Tg, at the surface was discerned to be markedly lower than its bulk Tg, and the discrepancy of Tg between surface and bulk becomes larger with the decreasing Mn. Such an intensive activation of thermal molecular motion at the PS surfaces can be explained in terms of an excess free volume in the vicinity of the film surface induced by the preferential segregation of chain end groups..
109. Tisato Kajiyama, Daisuke Kawaguchi, Noriaki Satomi, Keiji Tanaka, Atsushi Takahara, Surface glass transition behaviors of glassy polymers, Reports on Progress in Polymer Physics in Japan, 43, 311-330, 2000, Recent studies of thermal molecular motions at polymer surfaces are reviewed. Although many arguments have been still going on, many results support a consistent notion that surface molecular motion is much more vigorous than that in its interior bulk region. Finally, surface dynamics at temperature below its bulk glass transition is also reviewed..
110. Xiqun Jiang, Keiji Tanaka, Atsushi Takahara, Seiichi Nakahama, Tisato Kajiyama, Chain end group-induced surface ordering in poly(styrene-b-4-vinylpyridine) symmetric diblock copolymer films, Polymer Journal, 31, 11 pt 2, 1015-1020, 1999.12, The proton-terminated and fluoroalkyl-terminated poly(styrene-b-4-vinylpyridine) [P(St-b-4VP)] symmetric diblock copolymers were synthesized by a sequential anionic polymerization. The surface chemical composition, surface morphology and surface mechanical properties of the diblock copolymer thin films were investigated on the basis of the angular-dependent X-ray photoelectron spectroscopic (ADXPS) measurement and transmission electron microscopic (TEM) observations. The XPS results revealed that in the case of the proton-terminated P(St-b-4VP) film, the surface weight fraction of poly(4-vinyl pyridine)(P4VP) decreased dramatically after annealing above the glass transition temperature, Tg of P(St-b-4VP), resulting in the formation of polystyrene (PS) surface layer in order to minimize the interfacial free energy at air-polymer interface. Whereas, in the cases of the fluoroalkyl-terminated P(St-b-4VP) films [P(St-b-4VP)-C
2
C
F
X
where -C
2
C
F
X
shows fluoroalkyl end group], the surface weight fraction of P4VP decreased slightly and still was more than 30% even after the annealing treatment. TEM observation revealed that the lamellar structure was formed in all P(St-b-4VP). The surface order and orientation of lamellar structure were strongly influenced by the chain end group species. That is, in the case of the proton-terminated P(St-b-4VP) film, the lamellar structure was oriented parallel to the film surface and the outermost layer was composed of PS. On the other hand, in the case of P(St-b-4VP)-C
2
C
F
X
, the well-developed lamellae was tilted ca. 45 deg to the film surface and the alternating PS and P4VP layers were exposed to the air interface. These results indicate that the surface order and orientation of microphase-separated lamellar structure strongly depend on the chemical structure of the chain end group..
111. Tisato Kajiyama, Noriaki Satomi, Keiji Tanaka, Atsushi Takahara, Surface, thermal and mechanical characteristics of polymeric solids, Macromolecular Symposia, 10.1002/masy.19991430114, 143, 171-183, 1999.01, Surface molecular motions of amorphous polymeric solids have been directly measured on the basis of lateral force microscopic (LFM) and scanning viscoelasticity microscopic (SVM) measurements. SVM measurement revealed that the molecular motion at the surface of the monodisperse polystyrene (PS) film with Mn less than ca.30k was fairly activated compared with that in a bulk region, mainly due to the surface segregation of chain end groups. Tempereature dependent LFM and SVM measurement revealed that the surface glass transition temperature, Tg of the monodisperse PS film was lower than the bulk one, even though Mn was fairly large as 140k and also, that the time-temperature superposition was applicable to the surface relaxation process. The chain end group segregation at the air/PS interface was verified from the dynamic secondary ion mass spectroscopic (DSIM S) depth profiling of the proton and deuterium ion for the end-labeled deutrated-PS (dPS) film. These results suggest that the surface Tg is depressed due to an increase in free volume near surface region, being induced by the preferential surface localization of chain end groups..
112. Keiji Tanaka, Patricia A. Manning, Victor K. Lau, Hyuk Yu, Lipid Lateral Diffusion in Dilauroylphosphatidylcholine/Cholesterol Mixed Monolavers at the Air/Water Interface, Langmuir, 15, 2, 600-606, 1999, Binary monolayers of L-α-dilauroylphosphatidylcholine (DLPC) and cholesterol were formed at the air/water interface by the successive addition method with chloroform as the spreading solvent at 296 K. Translational diffusion of a probe lipid in the monolayers as a function of cholesterol fraction was examined by the technique of fluorescence recovery after photobleaching in conjunction with epifluorescence microscopy and the Wilhelmy plate method. A transition from biphasic morphology to a visually homogeneous uniphasic monolayer occurred at surface pressures between 13 and 20 mN·m -1, depending on the cholesterol fraction in the monolayer. The lateral diffusion coefficient was found to decrease when surface pressure and/or cholesterol fraction were/was increased. The diffusion coefficients of the probe lipid in the homogeneous monolayers were analyzed on the basis of the free area model. The observed retardation of the diffusion is ascribed to an increase in the in-plane surface viscosity of monolayers. In the case of biphasic binary monolayers, the retardation with increasing cholesterol fraction is attributed to the obstacle mediated diffusion as in the effective medium analysis as well as to increasing surface viscosity..
113. Atsushi Takahara, X. Jiang, N. Satomi, Keiji Tanaka, T. Kajiyama, Analysis of surface mechanical properties of polymer blend ultrathin films by scanning force microscopy, Key Engineering Materials, 137, 79-86, 1998.12, Scanning viscoelasticity microscopy (SVM) is used in studies of the surface mechanical properties of polymeric solids. It was revealed that the surface molecular motion is fairly different from bulk one due to the surface segregation of chain end groups. The two-dimensional mapping of the surface mechanical properties for the polymer blend ultrathin films was carried out on nanometer scale..
114. Won Ki Lee, Jeong Sik Yoon, Keiji Tanaka, Noriaki Satomi, Xiqun Jiang, Atsushi Takahara, Chang Sik Ha, Tisato Kajiyama, Relationships between lateral force and viscoelastic properties for amorphous polymer films based on lateral force microscopy, Polymer Bulletin, 10.1007/s002890050161, 39, 3, 369-376, 1997.01, The relationships between lateral force and viscoelastic properties of amorphous polymer surfaces with Tg's lower and higher than room temperature (295 K, RT) and their blend systems have been studied on the basis of lateral force microscopic (LFM) measurement. Under the conditions of scanning rate of 10
2
-10
5
nm sec
-1
, normal load of 5 nN and RT, the lateral forces of poly(methyl methacrylate) (PMMA) and polyisoprene (PI) homopolymers with Tg's fairly higher and lower than RT, respectively, did not depend on the scanning rate. Whereas, the lateral force of poly(methyl acrylate) (PMA) with Tg≤RT decreased with an increase in the scanning rate. Also, poly(vinyl acetate) (PVAc) with Tg≥RT showed slight dependence on the scanning rate. The scanning rate dependence of lateral force was similar to the frequency dependence of mechanical loss modulus. The results indicate that the magnitude of lateral force strongly depends on the state of thermal molecular motion. The lateral force-viscoelastic properties of miscible polymer blends was also investigated by LFM..
115. Tisato Kajiyama, Keiji Tanaka, Atsushi Takahara, Surface thermomechanical and glass transition temperature measurements of polymeric solids, Macromolecular Symposia, 10.1002/masy.19971180187, 118, 677-682, 1997.01, The surface molecular motion of polymeric solids was investigated on the basis of scanning force microscopic and temperature-dependent X-ray photoelectron spectroscopic measurements. The surface of the monodisperse polystyrene films was in a glass-rubber transition state even at 293 K in the case of number-average molecular weight less than ca. 30k. The surface glass transition temperature, Tgs for the symmetric poly(styrene-block-methyl methacrylate) diblock copolymer films were much lower than those for the bulk samples. A remarkable depression of Tg at the air-polymer interface was explained by the surface localization of chain end groups..
116. Atsushi Takahara, Keiji Tanaka, Shou Ren Ge, Tisato Kajiyama, Scanning force microscopic study of morphology and properties of multiphase polymer surface, Unknown Journal, 37, 2, 589-590, 1996.08.
117. T. Kajiyama, Keiji Tanaka, S. R. Ge, Atsushi Takahara, Morphology and mechanical properties of polymer surfaces via scanning force microscopy, Progress in Surface Science, 10.1016/0079-6816(96)00006-8, 52, 1, 1-52, 1996.01, Scanning force microscopy is used in studies of the surface morphology and surface mechanical properties of polymeric solids. Several examples are presented to illustrate that SFM is a powerful and promising tool for investigations, such as, polyethylene single crystal, polymer blend thin films and polymerized organosilane monolayers. The imaging of nano-mechanical properties, such as, lateral force and elastic modulus of phase-separated polymer surfaces by SFM is presented. The application of SFM to the quantitative evaluation of surface viscoelasticity is also summarized..
118. Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Surface molecular motion of polymeric solid films, KOBUNSHI RONBUNSHU, 10.1295/koron.53.582, 53, 10, 582-591, 1996.01, Surface dynamic storage modulus, E′, and surface loss tangent, tan δ, of monodisperse polystyrene (PS) films with various molecular weights were evaluated at 293 K on the basis of scanning viscoelasticity microscope (SVM) which was designed by the authors. In the case of the PS film with a number-average molecular weight, Mn, lower than ca. 30 k, the magnitudes of surface E′ and surface tan δ were smaller and larger than the magnitudes showing a glassy state, respectively. Thus, it seems reasonable to conclude that the PS film surface with Mn less than ca. 30 k is in a glass-rubber transition state even at 293 K. The scanning rate dependence of lateral force for the monodisperse PS films was investigated at 293 K by lateral force microscopy (LFM). Since the magnitude of lateral force was apparently dependent on the scanning rate, especially in the case of Mn lower than ca. 40 k, it seems reasonable to conclude that the PS film surface with Mn less than ca. 40 k is in a glass-rubber transition state at 293 K. The LFM results agreed well with the SVM results if the scanning rate of cantilever tip for LFM measurements corresponded to the measuring frequency for SVM measurements. The depth dependence of surface glass transition temperature, Tg, of the poly-(styrene-block-methyl methacrylate) diblock copolymer film was also investigated on the basis of the combination of temperature-dependent and angular-dependent X-ray photoelectron spectroscopic (TDXPS and ADXPS) measurements. It was revealed that Tg at the film surface was much lower than that of the bulk sample and its magnitude increased with the depth from the free surface. The remarkable depression of Tg at the polymeric surface was explained by the excess free volume induced due to the surface localization of chain end groups. The surface enrichment of chain end groups was confirmed by dynamic secondary ion mass spectroscopic measurement..
119. Keiji Tanaka, Toshiyuki Shikata, A special issue for rheology in surfaces, interfaces and thin films, Nihon Reoroji Gakkaishi, 36, 2, 2008.
120. Yoshihisa Fujii, Hironori Atarashi, Norifumi Yamada, Naoya Torikai, Toshihiko Nagamura, Keiji Tanaka, Gas sorption into surface of poly(methyl methacrylate) films at atmospheric Pressure, Polymer Journal, 10.1295/polymj.PJ2007070, 39, 12, 1290-1294, 2007.12, Interfacial structure of deuterated poly(methyl methacrylate) (dPMMA) and polystyrene (dPS) films with gases such as carbon dioxide (CO2) and nitrogen (Ni) under a pressure of 0.1 MPa was examined by neutron reflectivity (NR). The interface was analyzed using a model that the density of the outermost region of the films was lower than that of the interior region. The density profile was expressed by a single exponential equation with a decay length (ζ). The &zeta. values for the dPMMA films under CO2 and N2 were larger than that under vacuum at a given temperature, and the extent was more remarkable under CO2 than under N2. On the other hand, such a gas sorption was not clearly discerned for the dPS films. Finally, the surface relaxation in the dPMMA and dPS films under CO2 and N2 was discussed on the basis of lateral force measurements..
121. Yoshihisa Fujii, Kei Ichi Akabori, Keiji Tanaka, Toshihiko Nagamura, Chain conformation effects on molecular motions at the surface of poly(methyl methacrylate) films, Polymer Journal, 10.1295/polymj.PJ2006270, 39, 9, 928-934, 2007.11, Surface relaxation in syndiotactic (st-) and isotactic (it-) poly(methyl methacrylate) (PMMA) films was studied by lateral force microscopy. The αa- and β-relaxation processes were clearly observed even at the surface, permitting us to deduce the form of the dispersion map for the surface relaxation processes. Both relaxation temperatures at the surface were lower than the corresponding ones in the bulk. In addition, the extent to which the peak temperature for the surface relaxation processes fell below that of the bulk strongly depended on the stereoregularity of the films. The differences in the chain conformations between the surface and the bulk, which were more remarkable in the st-PMMA, produced this variation in surface mobility..
122. Kei Ichi Akabori, Keiji Tanaka, Noriaki Satomi, Toshihiko Nagamura, Atsushi Takahara, Tisato Kajiyama, Effects of static and dynamic forces on surface viscoelastic response of polymer films in scanning viscoelasticity microscopy, Polymer Journal, 10.1295/polymj.PJ2006230, 39, 7, 684-689, 2007.09, Scanning force microscopy with force-modulation mode enables one to gain direct insights into local viscoelastic properties at polymer surfaces. Changing modulation condition such as dynamic amplitude and frequency in addition to static normal force, surface viscoelastic response of polystyrene (PS) film was studied. If dynamic and/or static forces were/was ill-chosen, non-linearity of viscoelastic response became dominant, resulting in hole formation at the surface. On the contrary, if they were appropriately adjusted, linear viscoelastic measurement could be realized in the frequency range from 10 Hz to 4 kHz. This leads to traditional rheological analysis even at the surface..
123. Keiji Tanaka, Tawa Keiko, Study on Nano-physical Properties of Polymer Solids for the Near Future, Kobunshi, 10.1295/kobunshi.56.38, 56, 1, 2007.09.
124. Keiji Tanaka, Tawa Keiko, The Direction of My Future Research in the Field of Polymer Science, Kobunshi, 10.1295/kobunshi.56.38a, 56, 1, 2007.09.
125. Yohei Tateishi, Keiichi Akabori, Keiji Tanaka, Toshihiko Nagamura, Hierarchical thermal molecular motion in thin polymer films, KOBUNSHI RONBUNSHU, 10.1295/koron.64.429, 64, 7, 429-436, 2007.07, Hierarchical thermal molecular motion was studied in thin films of polystyrene (PS). The segmental motion in the thin films was examined by dynamic mechanical analysis. Molecular motions with a relatively small scale in the thin films were discussed on the basis of the kinetics of photoinduced trans to cis isomerization for azobenzene probes tagged to PS. Apparent glass transition temperatures generally decreased with decreasing film thickness. Although relaxation temperatures of β and γ processes in the thin films would be comparable to those in the bulk, the photoisomerization reaction of azobenzene probes became faster with decreasing thickness. Finally, a model for hierarchical thermal molecular motions in thin films was proposed on the basis of the above-mentioned results..
126. Yohei Tateishi, Keiji Tanaka, Toshihiko Nagamura, Kinetics of photoinduced E to Z isomerization of azobenzene in polystyrene films
Thickness, molecular weight and temperature effects, Journal of Physical Chemistry B, 10.1021/jp0705065, 111, 27, 7761-7766, 2007.07, E to Z (trans → cis) photoisomerization of azobenzene (Az) chromophores tagged to polystyrene (PS) in thin films was studied as functions of thickness, PS molecular weight, and temperature, using the change in absorption at 336 nm arising from the Az E isomer remaining upon ultraviolet light irradiation at 350 ± 5 nm. The photoisomerization in solid films exhibited fast and slow modes. The fractional amount of the fast mode (I 1) started to increase with decreasing film thickness once the films were thinner than a threshold value. This was explained in terms of a surface layer in which the photoisomerization reaction proceeds quickly, the effect of which becomes more noticeable with decreasing thickness due to a larger surface to volume ratio. The thickness dependence of the I1 fraction was insensitive to the molecular weight of the PS used. The thickness of the surface layer, estimated through a layer model analysis, increased with rising temperature up to 298 K. Interestingly, the surface layer markedly thickened at temperatures at which the molecular motion of PS is on a relatively small scale, namely, at the γ and β relaxation temperatures..
127. Hironori Atarashi, Kei Ichi Akabori, Akihiro Tanaka, Masaaki Ozawa, Keiji Tanaka, Toshihiko Nagamura, Graft polymerization initiated by photosensitizer segregated at surface of polymer film upon ultraviolet irradiation, Chemistry Letters, 10.1246/cl.2007.808, 36, 6, 808-809, 2007.06, A novel approach to surface modification of polymer films is proposed on the basis of graft polymerization initiated from photosensitizers attached to hyperbranched polymers which are localized at the film surface..
128. Kei Ichi Akabori, Keiji Tanaka, Toshihiko Nagamura, Atsushi Takahara, Tisato Kajiyama, Thermal molecular motion in polystyrene thin and ultrathin films by dynamic viscoelastic measurement, Journal of Central South University of Technology (English Edition), 10.1007/s11771-007-0279-6, 14, 1 SUPPL., 346-349, 2007.02, Segmental motion in polystyrene (PS) thin and ultrathin films supported on substrates was studied by dynamic viscoelastic measurement. A polymer film, which has the thickness comparable to or less than twice of radius of gyration of an unperturbed chain (2R g), is defined as an ultrathin film. In the case of PS, α a-relaxation process corresponding to the segmental motion was generally observed at approximately 380 K. Even for both the PS thin and ultrathin films, the α a-absorption peak was clearly observed. A rheological analysis reveals that the α a-relaxation behavior for the thin films with the thickness of about 200 nm is the same as that of the bulk sample. On the contrary, in the case of the PS ultrathin films, the α a-absorption peak on temperature-loss modulus (E) curve is broadened toward both lower and higher temperature sides. This can be interpreted by taking into account that the segmental motion in the vicinity of surface and interface is detectable for such ultrathin films, which should be faster and slower than that in the bulk, respectively. And, it is found that the apparent activation energy (ΔH) for the α a-relaxation in the ultrathin films becomes smaller than the bulk value probably due to the surface effect. Finally, an interfacial effect on the ΔH was studied by using different substrates. When the interaction between PS and substrate becomes stronger, the ΔH value for the α a-relaxation in the ultrathin films increases. The results imply that the segmental motion in the polymer ultrathin films is strongly influenced by surface and interfacial effects..
129. Kazuo Kato, Takashi Aoki, Yasushi Okamoto, Keiji Tanaka, Atsushi Takahara, Reliability analysis of adhesive for PBT-epoxy interface, 2007 World Congress 2007 World Congress, 2007, PBT (polybutylene terephthalate) and epoxy adhesive, which both have superior heat resistance and environmental resistance, are a representative combination now being applied to many parts. Generally, PBT is annealed after molding at a temperature above the glass transition temperature to ensure dimensional stability when in use. But in this case, this process decreases the adhesive strength between PBT and epoxy. This study analyzes the adhesion degradation mechanism in this system and a countermeasure technology is proposed. Regarding this PBT-epoxy adhesion degradation mechanism, focus is placed on changes in the fracture surface, which is analyzed before and after annealing. From this analysis it becomes clear that generation of a WBL (weak boundary layer) is caused by non-crystallization and a migration of the PBT functional group on the adhesion surface layer. According to this mechanism, it is clear that control of the functional group on the surface layer and reforming of a new functional group are very effective ways to maintain adhesive strength after annealing..
130. Masahiro Hino, Masaaki Kitaguchi, Hirotoshi Hayashida, Yuji Kawabata, Seiji Tasaki, Toru Ebisawa, Dai Yamazaki, Ryuji Maruyama, Keiji Tanaka, Naoya Torikai, Rintaro Inoue, Toshiji Kanaya, A test of MIEZE-reflectometer for study of surface and interface, Physica B: Condensed Matter, 10.1016/j.physb.2006.05.388, 385-386, 1125-1127, 2006.11, We have installed a MIEZE-type spin echo spectrometer at the C3-1-2-2 (MINE1) port at the JRR-3 M in the Japan Atomic Energy Agency. By combining neutron reflectometry and the MIEZE, it is possible to detect inelastic and quasi-elastic scattering on the surface and at the interface. We have succeeded in measuring a MIEZE signal for which the Fourier time is up to 0.8 ns. Though the Fourier time is small, we tested several samples by the MIEZE reflectometer..
131. Hiroshi Morita, Keiji Tanaka, Tisato Kajiyama, Toshio Nishi, Masao Doi, Study of the glass transition temperature of polymer surface by coarse-grained molecular dynamics simulation, Macromolecules, 10.1021/ma052632h, 39, 18, 6233-6237, 2006.09, The glass transition temperature at the surface of polymer film is studied by the coarse-grained molecular dynamics simulation. By the analysis of the segmental motion, the glass transition temperatures at the surface region and that in the bulk region are determined separately. The glass transition at the surface region is found to be lower than that in the bulk region. The molecular weight dependence of the glass transition temperature obtained by the simulation agrees well with that obtained by the scanning force microscopic measurements..
132. Daisuke Kawaguchi, Keisuke Masuoka, Atsushi Takano, Keiji Tanaka, Toshihiko Nagamura, Naoya Torikai, Robert M. Dalgliesh, Scan Langridge, Yushu Matsushita, Comparison of interdiffusion behavior between cyclic and linear polystyrenes with high molecular weights, Macromolecules, 10.1021/ma060652t, 39, 16, 5180-5182, 2006.08, The interdiffusion behavior between cyclic and linear polystyrenes with high molecular weight based on dynamic secondary ion mass spectroscopy (DSIMS) in conjunction with neutron reflectivity (NR) measurements was investigated. Polymers used in this study are monodisperse cyclic and linear PSs (c-hPS, 1-hPS) and those deuterated counterparts (c-dPS, 1-dPS). Time evolution of interfacial thickness with annealing was evaluated by NR and DSIMS. The broadening of the (c-hPS/c-dPS) interface takes place much more rapidly than that of corresponding linear ones. The diffusion of cyclic polystyrene is much faster than that of linear polystyrene. Both thickness of (c-hPS/c-dPS) and (1-hPS/1-dPS) interfaces increase with increasing temperature at 120°C, and that of (c-hPS/c-dPS) bilayer films is much higher than that of (1-hPS/1-dPS) ones at any given temperature..
133. Keiji Tanaka, Glass transition of polymers in confined systems, KOBUNSHI RONBUNSHU, 10.1295/koron.63.539, 63, 8, 539-547, 2006.08, In this paper, glass transitions of polystyrene (PS) in confined geometry such as ultrathin state, surface and interface were studied. Dynamic mechanical analysis was successfully used to characterize polymer ultrathin films supported on substrates. This method allowed us to uncover the effects of the free surface and the substrate interface on the segmental dynamics in PS films with various thickness. As the film thickness decreased, the distribution of relaxation times for the segmental motion became broader, a change mainly due to surface and interfacial effects. The results obtained in this study imply that two contrasting effects exist: the effect of the free surface accelerates the segmental motion, whereas interfacial interaction produce the opposite effect. This was also confirmed by independent experiments related to glass transition temperature at the surface and the interface by scanning force microscopy and time- and space-resolved fluorescence spectroscopy, respectively..
134. Daisuke Kawaguchi, Atsushi Takano, Yushu Matsushita, Naoya Torikai, Keiji Tanaka, Toshihiko Nagamura, Robert Dalgliesh, Sean Langridge, Comparison of molecular motion between linear polystyrenes and cyclic polystyrenes with same molecular weight, 55th Society of Polymer Science Japan Symposium on Macromolecules 55th SPSJ Symposium on Macromolecules, 55, 3131-3132, 2006, Time evolution of interfacial thicknesses between a cyclic polystyrene (c-hPS) / its deuterated counterpart (c-dPS) and a linear polystyrene (1-hPS) / its deuterated counterpart (1-dPS) bilayer films was investigated by dynamic secondary ion mass spectrometry (DSIMS) and neutron reflectivity (NR). The interfacial thickness of (c-hPS/c-dPS) film was significantly larger than that of (1-hPS/1-dPS) film at any given annealing time, indicating that the diffusion constant of c-PS is constantly larger than that of 1-PS. It might be explained that weaker topological constraint comes from the entanglement for the c-PS than for the 1-PS..
135. Yasushi Okamoto, Kazuo Kato, Takashi Aoki, Takao Izumi, Keiji Tanaka, Osami Sakata, Atsushi Takahara, Tisato Kajiyama, Effect of annealing treatment and surface treatment on adhesion behavior of poly(butylene terephthalate), 55th SPSJ Annual Meeting Polymer Preprints, Japan - 55th SPSJ Annual Meeting, 55, 1136, 2006, Influence of annealing treatment on adhesion behavior of poly(butylene terephthalate) (PBT) with epoxy adhesive was studied. The tensile adhesion strength decreased after the annealing treatment of PBT. In the case of the untreated PBT, the failure depth after the failure was not clearly defined. Once the PBT was annealed, the average failure depth turned to be 4 nm. The above results imply that the failure mechanism for the system transformed from interfacial failure to cohesive fracture upon annealing treatment. This can be easily understood by taking into account that a mechanically weak layer is formed in the surface region of PBT after the annealing. Such a weak boundary layer was observed by scanning viscoelasticity microscopy. Improvement of adhesive property was confirmed by surface treatment..
136. Yasushi Okamoto, Kazuo Kato, Takashi Aoki, Takao Izumi, Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Influence of plasma treatment on adhesion behavior of poly(butylene terephthalate), 55th Society of Polymer Science Japan Symposium on Macromolecules 55th SPSJ Symposium on Macromolecules, 55, 3442, 2006, An effect of surface treatment on adhesion behavior of poly (butylene terephthalate) (PBT) with epoxy adhesive was studied. In general, PBT is annealed at a temperature above the glass transition temperature to obtain dimensional stability for the practical use. However, such an annealing procedure makes the adhesion properties poorer. In this study, we demonstrate that tensile adhesive strength for annealed PBT could be improved through plasma treatment. Tensile adhesive strength increased with increasing surface density of C-O and COO groups, which were quantitatively detected by XPS. Finally, it was concluded that chemical interaction between carboxyl and/or ester groups of PBT and hydroxyl groups of epoxy adhesive was a responsible factor in improving adhesive strength between PBT and epoxy adhesive..
137. Masaya Hikita, Tetsuya Nakamura, Keiji Tanaka, Tisato Kajiyama, Atsushi Takahara, Liquid repellent properties of patterned surfaces and their applications to polymeric materials, 55th SPSJ Annual Meeting Polymer Preprints, Japan - 55th SPSJ Annual Meeting, 55, 1264, 2006, It was studied how liquid repellent properties can be controlled on the basis of roughness at surfaces. Ultrafine-patterned surfaces were prepared by the photolithography. The surfaces were fully covered with fluoroalkyl silane coupling agent by chemical vapor deposition (CVD) for about two hours. Contact angle to water increased as increasing pitch of the pattern. The relation between water contact angle and pitch was well expressed by the Cassie mode, where assumed that the space between solid surface and water was occupied by air. Contact angle to dodecane was neither in agreement with Wenzel nor Cassie's modes. Instead, in the case of dodecane, both modes should be combined to reproduce the experimental results. Hence, it can be claimed that factors such as increase in surface area and formation of air layer at the interface between liquid and surface are important for excellent liquid repellent properties..
138. Keiichi Akabori, Kazuyuki Oya, Hiroki Murase, Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Nano-rheological analysis of polymer cross-section films prepared by a mechanical cutting method, 55th SPSJ Annual Meeting Polymer Preprints, Japan - 55th SPSJ Annual Meeting, 55, 1270, 2006, A cross-section film of a symmetric diblock copolymer, in which lamellar structure was formed, was successfully prepared by a mechanical cutting method using a sharp diamond knife. In this method, the knife was obliquely pushed into the sample from the surface side. The oblique angle was precisely controlled to be 0.57 deg. Thus, periodic lamellar structure was shown up at the surface of the cross-section film Then, scanning viscoelasticity microscopy (SVM), which can image viscoelastic information at the surface, was applied to the cross-section film. Finally, it was demonstrated that a combination of SVM and mechanical cutting method enabled one to gain direct insight into the depth information for structure and physical properties of the diblock copolymer film along the direction normal to the surface..
139. Kazuyuki Oya, Keiichi Akabori, Hiroki Murase, Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Nano-rheological analysis of polymer thin films prepared by gradient shaving method, 55th Society of Polymer Science Japan Symposium on Macromolecules 55th SPSJ Symposium on Macromolecules, 55, 3095-3096, 2006, In order to investigate structure of diblock copolymer thin film, gradient shaved surface was prepared by using Surface And Interfacial Cutting Analysis System (SAICAS). The scanning viscoelasticity microscopic observation of sliced film revealed the alternate lamellar structures with different mechanical properties in the depth direction..
140. Tomoyuki Koga, Shigekazu Yasutake, Keiji Tanaka, Keiichi Akabori, Kazunori Andou, Tisato Kajiyama, Atsushi Takahara, Evaluation of surface mechanical properties of organic ultrathin films using scanning force microscope, 54th SPSJ Symposium on Macromolecules 54th SPSJ Symposium on Macromolecules - Polymer Preprints, Japan, 54, 3840-3841, 2005.12, Surface mechanical properties of polystyrene (PS) film prepared from single droplet of PS solution by ink-jet (IJ) method, and [PS / Polybutadiene (BDA)] (60/40, w/w) blend film were investigated by scanning force microscope. The scanning viscoelesticity microscopic measurements at various temperatures clarified that the relative difference of contrast of the PS and the PBD phase surface becomes small with an increase of temperature. This is due to the relative difference of elasticity of PS and PBD phases. Based on the temperature dependent lateral force measurements, the surface of the PS film prepared by IJ method was in a glass-rubber transition state even at 343 K, in spite of that the bulk Tg was far above 343 K [Tg (bulk)=378 K]. Similar temperature dependence of lateral force was also observed on the PS film prepared by spin-coating method..
141. Atsushi Sakai, Keiji Tanaka, Yoshihisa Fujii, Toshihiko Nagamura, Tisato Kajiyama, Erratum
Structure and thermal molecular motion at surface of semi-crystalline isotactic polypropylene films (Polymer (2005) 46 (429-437) DOI: 10.1016/j.polymer.2004.11.021), Polymer, 10.1016/j.polymer.2004.12.036, 46, 5, 2005.02.
142. Shigeki Nakahara, Masanori Motowoka, Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Evaluation of interfacial structure in blends of polypropylene and elastomer by scanning force mircroscopy, KOBUNSHI RONBUNSHU, 10.1295/koron.62.432, 62, 9, 432-434, 2005.01, Flat cross-sections of (polypropylene/elastomer) blends were prepared by ultamicrotoming at 150 K. Then, scanning force microscopy (SFM) was applied to each cross-section to evaluate the interfacial thickness between the two phases in the blend. For this purpose, a viscoelastic mode was superior to a conventional topographic mode. The results obtained well reflected the solubility between the two components. Finally, transmission electron microscopy was applied to the sample. The TEM observations supported what was suggested on the basis of SFM results..
143. Yasushi Okamoto, Kazuo Kato, Takashi Aoki, Takao Izumi, Keiji Tanaka, Osami Sakata, Sono Sasaki, Atsushi Takahara, Tisato Kajiyanm, An effect of surface treatment on adhesion behavior of poly (butylene terephthalate), 54th SPSJ Symposium on Macromolecules 54th SPSJ Symposium on Macromolecules - Polymer Preprints, Japan, 54, 3289-3290, 2005, An effect of surface treatment on adhesion behavior of poly (butylene terephthalate) (PBT) with epoxy adhesive was studied. In general, PBT is supposed to be annealed at a temperature above the glass transition temperature to obtain dimensional stability for the practical use. However, such an annealing procedure makes the adhesion properties poorer. In this study, we demonstrate that tensile adhesive strength for annealed PBT could be improved through UV irradiation or chemical etching treatment. Tensile adhesive strength increased with increasing surface density of C-O and C=O groups, which were quantitatively detected by XPS. Finally, it was concluded that chemical interaction between carboxyl and/or ester groups of PBT and hydroxyl groups of epoxy adhesive was a responsible factor in improving adhesive strength between PBT and epoxy adhesive..
144. Keigo Aoi, Takaaki Fukui, Yoshiharu Otsuka, Keiji Tanaka, Toshihiko Nagamura, Architecture and shape control of nanoobjects based on amphiphilic dendrimers, 54th SPSJ Symposium on Macromolecules 54th SPSJ Symposium on Macromolecules - Polymer Preprints, Japan, 54, 2715-2716, 2005, In the field of nanotechnology and nanoscience, dendrimers are key compounds having well-defined chemical structure. We nave already reported synthesis of globular carbohydrate macro molecule "sugar ball" which is applicable to gene and drug carriers [1-4]. Amphiphilic surface-sugar- substituted surface-block dendrimers have been also designed, synthesized and characterized [4]. Supramolecular architeucture based on amphiphilic dendrimers is important to create shape controlled smart nanoobjects[5]. The present report deals with synthesis and assembly of amphiphilic sugar-substituted poly(ethylene glycol) dendrimers. The dendrimers were synthesized by the reaction of N-acetyl-D-glucosamine, galactose, and lactose derivatives with poly(ethylene glycol) dendrimer having a hydroxy group and alkyl groups at the core and the surface, respectively, wnich were prepared by convergent method. The sugar moieties and the poly(ethylene glycol) dendrimer branches are regarded as hydrophilic parts, whereas the alkyl groups act as hydrophobic groups. Although hydrophobicity of the amphiphilic dendrimers is high, nanoparticles based on the amphiphilic dendrimers can be prepared by irradiation of ultrasonic wave. Fortunately the particle size, which is measured using DLS, could be controlled around ca. 200 nm. Monolayer of the amphiphilic dendrimers was successfully formed at the air/water interface. Intermolecular distance, i.e., intersugar distance, of the monolayer was found to be controlled around 2 nm by changing generation and hydrophobic groups of the dendrimers..
145. Keiichi Akabori, Keiji Tanaka, Toshihiko Nagamura, Atsushi Takahara, Tisato Kajiyama, Effect of substrate interface on mechanical relaxation behavior in polymer ultrathin films, 54th SPSJ Annual Meeting 2005 54th SPSJ Annual Meeting 2005 - Polymer Preprints, Japan, 54, 925, 2005, Mechanical relaxation behavior of polystyrene (PS) and poly (2-vinylprydine) (P2VP) thin and ultrathin films on substrates was examined. Even in the case of the ultrathin films, the α2-relaxation process corresponding to the segmental motion was successfully observed. However, the αa-absorption peak was broadened toward lower and higher temperature sides because of surface and interfacial effects. Interestingly, when a PS ultrathin film was sandwiched between SiOx layers, an additional peak come up with the interfacial segmental motion appeared at the higher temperature side. In the case of the P2VP ultrathin films on the SiOx substrates, the interfacial effect became remarkable due to the strong attractive interaction between chains and the substrate. Finally, it was concluded that chain mobility in the interfacial region was depressed in comparison with that in the internal bulk phase..
146. Yasushi Okamoto, Kazuo Kato, Takao Izumi, Keiji Tanaka, Osami Sakata, Atsushi Takahara, Tisato Kajiyama, Influence of annealing treatment on adhesion behavior of poly(butylene terephthalate), 54th SPSJ Annual Meeting 2005 54th SPSJ Annual Meeting 2005 - Polymer Preprints, Japan, 54, 879, 2005, Influence of annealing treatment on adhesion behavior of poly(butylene terephthalate) (PBT) with epoxy adhesive was studied. The tensile adhesion strength decreased after the annealing treatment of PBT. In the case of the untreated PBT, the failure depth after the failure was not clearly defined. Once the PBT was annealed, the average failure depth turned to be 4 nm. The above results imply that the failure mechanism for the system transformed from interfacial failure to cohesive fracture upon annealing treatment. This can be easily understood by taking into account that a mechanically weak layer is formed in the surface region of PBT after the annealing. Such a weak boundary layer was observed by grazing incidence X-ray diffraction measurement..
147. Keiji Tanaka, Polymer nano-adhesion promoted by surface molecular motion, 54th SPSJ Annual Meeting 2005 54th SPSJ Annual Meeting 2005 - Polymer Preprints, Japan, 54, 109-111, 2005, Polymer nano-adhesion was studied. Polystyrene (PS) bilayer was prepared by attaching original two PS film surfaces together, and was annealed at a temperature between surface and bulk glass transition temperatures for a given time. Discernible interfacial adhesion strength (G) was observed, and was proportional to the interfacial width of a few nanometers measured by dynamic secondary ion mass spectrometry. This means that G at the (PS/PS) bilayer interface is mainly governed by interfacial thickening. Then, nano-adhesion test in between PSs was made using scanning force microscopy. The G value so obtained was larger than that for the bilayer by approximately 500 times under the same condition. The difference was accounted for by the completeness of the interfacial formation..
148. Keiichi Akabori, Hiroki Murase, Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Quantitative evaluation of nano-mechanical properties at polymer surfaces based on scanning viscoelasticity microscopy, 54th SPSJ Symposium on Macromolecules 54th SPSJ Symposium on Macromolecules - Polymer Preprints, Japan, 54, 3291-3292, 2005, A mechanical model analysis for scanning viscoelasticity microscopic (SVM) measurement under various conditions was carried out to quantitatively evaluate spring constants of polymer surfaces. Experiment was made at room temperature using polystyrene films with different molecular weights. When the sample surface was in a glassy state, that is, in an elastic regime, a series model composed of two springs with a cantilever and the sample surface could well express the SVM vibration system. In contrast, when the surface was in a viscoelastic regime, a viscous component must introduced into the model in order to analyze the experimental results. Based on fitting parameters for the analysis, the spring constants for the PS surfaces were successfully extracted. Consequently, the spring constants of the surfaces were lower than the bulk value by a few decades. Finally, it can be claimed that surface nano-mechanical properties are essentially different from the corresponding bulk ones..
149. Keuchi Akabori, Hiroki Murase, Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Quantitative evaluation of spring constant of a cantilever based on scanning viscoelasticity microscopy, 54th SPSJ Annual Meeting 2005 54th SPSJ Annual Meeting 2005 - Polymer Preprints, Japan, 54, 936, 2005, A mechanical model analysis was conducted to evaluate quantitatively spring constants for cantilevers and polymer surface via scanning viscoelasticity microscopic (SVM) measurement. The amplitude of dynamic displacement was set to be 5 nm, and the frequency was varied in the range of 101 - 2×103 Hz. Under such the condition, the cantilevers and the polystyrene (PS) surface exhibited elastic nature. An analysis using mechanical model could well reproduce the experimental results. Based on fitting parameters for the analysis, the spring constants for the cantilevers and the PS surface were extracted. Finally, it was concluded that surface mechanical properties in polymer films would be essentially different from the corresponding bulk ones..
150. Masaya Hikita, Tetsuya Nakamura, Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Super-water-repellent coating on polymer substrates using fluorosilane-silica hybrid materials, 54th SPSJ Annual Meeting 2005 54th SPSJ Annual Meeting 2005 - Polymer Preprints, Japan, 54, 1573, 2005, The purpose of this study is to develop transparent super-water-repellent surfaces with a simple way and to apply this coating to polymer substrates. Super-water-repellent surfaces are generally made by controlling chemistry and roughness at the surface. In this study, surface roughness was controlled by the content of colloidal silica particles in a sol-gel thin film covered with fluoroalkyl silane coupling agent. When the fractional amount of colloidal silica was in the range of 10-30 wt%, root mean square roughness at the surface by AFM was around 30-70 nm. X-ray photoelectron spectroscopy revealed that these surfaces were covered with fluoroalkyl groups. Consequently, these surfaces exhibit excellent water repellencies such as contact angles of 150 deg. to water. This coating procedure can be applied to transparent polymer substrates such as poly(ethyleneterephtarate) (PET) films. In that case, transparency and durability of the sol-gel layer on the PET film are sufficient enough to be applied for practical use..
151. Yoshihisa Fujii, Kazuhiro Koguchi, Keiji Tanaka, Toshihiko Nagamura, Atsushi Takano, Yushu Matsushita, Tisato Kajiyama, Surface relaxation behavior in cyclic polystyrene films, 54th SPSJ Annual Meeting 2005 54th SPSJ Annual Meeting 2005 - Polymer Preprints, Japan, 54, 928, 2005, Well-defined cyclic polystyrenes (c-PS) with various molecular masses were prepared by the reaction of linear polystyrene with two end vinyl groups and potassium naphthalenide as a coupling agent. Then, surface relaxation behavior in c-PS films was examined by lateral force microscopy (LFM). The αa-relaxation process corresponding to the segmental motion was clearly observed at the surface in the c-PS films. Surface glass transition temperature so obtained was approximately 300 K, which was lower than the bulk value, and was independent of the molecular weight due to the absence of chain ends. The results indicate that the molecular motion at the polystyrene surface is activated by not only chain ends but also other factors..
152. Hideaki Yokoyama, Takayuki Miyamae, Seok Han, Takashi Ishizone, Atsushi Takahara, Keiji Tanaka, Naoya Torikai, Surface segregation of watersoluble-hydrophobic block copolymers, 54th SPSJ Annual Meeting 2005 54th SPSJ Annual Meeting 2005 - Polymer Preprints, Japan, 54, 974, 2005, A block copolymer of deuterated polystyrene (dPS) and 2-[2-(2- methoxyethoxy)ethoxy]ethyl methacrylate (PME3MA) spontaneously exposes the PME3MA block, which is soluble in water, to the surface in a vacuum. dPS-PME3MA mixed with polystyrene (PS) segregates to the PS surface spontaneously and changes the hydrophobic PS surface into hydrophilic surface. The detail of the segregation will be discussed..
153. Hirohiko Yakabe, Keiji Tanaka, Toshihiko Nagamura, Tisato Kajiyama, Thermal molecular motion of polyethylene thin films, 54th SPSJ Annual Meeting 2005 54th SPSJ Annual Meeting 2005 - Polymer Preprints, Japan, 54, 926, 2005, Melting and relaxation behaviors in thin films of high-density and linear low-density polyethylene (HDPE and LLDPE) were examined by microthermal analysis and dynamic viscoelastic measurements, respectively. Melting point (T m) in HDPE and LLDPE films, respectively, increased and decreased with decreasing thickness. In the case of the HDPE films, the amorphous content decreased with decreasing thickness. This leads to that molecular motion of chains involved in the crystalline region is depressed with decreasing thickness. In contrast, although the amorphous content also decreased with decreasing thickness for the LLDPE films, it is not so small. Invoking that molecular motion in the amorphous region becomes active and dominates with decreasing film thickness, it can be understood that T m decreased with thickness for the LLDPE films..
154. Tisato Kajiyama, Ken Kojio, Keiji Tanaka, Aggregation states and molecular motion of polymer ultrathin films prepared at the air/water interface, Advances in Colloid and Interface Science, 10.1016/j.cis.2004.09.007, 111, 3 SPEC. ISS., 159-179, 2004.12, The preparation of poly(amido amine) (PAMAM) dendrimer monolayers at the air/water interface was analyzed. Investigations show the transfer of PAMAM dedrimer monolayers from the air side onto hydrophobic silicon wafers, which were treated by the horizontal lifting method. X-ray reflectivity, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques were used to study the aggregation states in the PAMAM monolayers. The results show that the PAMAM molecules sit on the substrate with an oblate shape in which the hydrophilic core and hydrophobic alkyl end groups were towards the substrate and air sides..
155. Keiji Tanaka, Study on Surface Glass Transition Behavior in Monodisperse Polystyrene Films, Nihon Reoroji Gakkaishi, 10.1678/rheology.32.17, 32, 1, 17-25, 2004.05, Surfaces in polymeric materials play an important role in many technological applications. Hence, systematical understanding of aggregation states and physical properties at the surfaces is of pivotal importance as the first benchmark so that highly functionalized polymeric materials based on surface peculiarity can be promisingly designed and constructed. Nevertheless, surface properties, especially rheological properties, had not been studied until early 90s because of technical difficulties. In 1993, we started to embark on this intriguing and challenging issue by mainly scanning force microscopy using monodisperse polystyrene (PS) solid films. Consequently, conclusions obtained thus far are consistently arrived that molecular motion at the PS surfaces is thermally activated in comparison with the corresponding internal bulk region. However, it is far from clear for the moment what the whole picture of such peculiar surface mobility is, although we believe that some parts of it have been successfully clarified to date. Here, experimental methods to examine surface rheological properties, which we have proposed, are mentioned at first, and then, essential points of what we have established are discussed..
156. Tisato Kajiyama, Daisuke Kawaguchi, Keiji Tanaka, Surface Mobility in Monodisperse Polystyrene Films, Macromolecular Symposia, 10.1002/masy.200351111, 201, 95-102, 2003.09, Surface dynamics in monodisperse polystyrene films was examined by lateral force microscopy in conjunction with dynamic secondary ion mass spectroscopy. Glass transition temperature, Tg, at the surface was markedly lower than the corresponding bulk Tg. Also, it was shown that polymer chains present at the surface could diffuse even at a temperature below the bulk Tg. The surface depth, in which molecular motion was activated, was of the order of 5 nm..
157. Tisato Kajiyama, Keiji Tanaka, Atsushi Takahara, Nano-rheological properties of polymeric solid surfaces, Nihon Reoroji Gakkaishi, 10.1678/rheology.31.33, 31, 1, 33-40, 2003.06, Surface rheological analyses of polymeric solids were presented on the basis of scanning viscoelasticity microscopy (SVM) and lateral force microscopy (LFM). SVM observation for phase-separated polymer blend films revealed two-dimensional distribution of elasticity. In order to study surface thermal molecular motion of monodisperse polystyrene (PS), SVM and LFM measurements were made at various temperatures. Glass transition temperature, Tg, at the surface was discerned to be markedly lower than the corresponding bulk Tg, and the discrepancy of Tg between surface and bulk became larger with decreasing molecular weight. Such an intensive activation of thermal molecular motion at the PS surface can be explained in terms of an excess free volume induced by the segregated chain ends and a reduced cooperativity at the surface. Bulk Tg of miscible binary blends can be well expressed by the Gordon-Taylor equation. Extending this notion to surface, the surface composition in blends would be obtained by measuring surface Tg of each constituent as well as their blend. The surface composition in blend films of two PSs with different molecular weights was experimentally and systematically elucidated. The surface enrichment of a smaller molecular weight component became more remarkable with increasing molecular weight disparity between the two components due probably to an entropic effect..
158. Tisato Kajiyama, Daisuke Kawaguchi, Keiji Tanaka, Polymer chain diffusion at a temperature below its bulk glass transition temperature, Chinese Journal of Polymer Science (English Edition), 21, 2, 141-146, 2003.03, In this study, it was examined whether the dynamics of polymer chains at a surface is different from that in the bulk, and if so, to what extent they differ in terms of surface glass transition temperature and diffusion coefficient. Obtained results clearly indicate that surface chains can travel for a relatively large distance in comparison with the characteristic length scale of usual segmental motion even at a temperature below its bulk glass transition temperature, Tg
b. This is consistent with our previous results that the surface glass transition temperature is much lower than the corresponding Tg
b. Also, it was experimentally revealed that there was a gradient of molecular motion in the surface region..
159. Tisato Kajiyama, Keiji Tanaka, Atsushi Takahara, Surface thermal molecular motion of chain end-modified polystyrenes, Macromolecular Symposia, 10.1002/masy.200390036, 192, 265-270, 2003.03, Surface glass transition temperature, Tg
s, of three classes of monodisperse polystyrene, proton-terminated (PS-H), α,ω-diamino-terminated (α,ω-PS(NH2)2) and (α,ω-dicarboxy-terminated (α,ω-PS(COOH)2), were studied by scanning force microscopy. Tg
s of all samples was discernibly lower than the corresponding bulk glass transition temperature, Tg
b. Also, Tg
s value was strongly dependent on what the chemical structure of chain end groups was. Based on the time-temperature superposition principle, apparent activation energy of the αarelaxation process corresponding to surface segmental motion was evaluated to be approximately 230 kJ•mol-1. This value was much smaller than the reported bulk ones, and was independent of the chemical structure of chain ends. This result implies that the cooperativity for the αa-relaxation process at the PS surface is reduced in comparison with the bulk due probably to an existence of the free space presented to polymer segments at the surface. Hence, it was concluded that the surface αa-relaxation process was activated by not only the chain end effect but also the reduced cooperativity at the surface..
160. Keiji Tanaka, Hyuk Yu, Lipase activity on lipid/polymer binary monolayers
Lateral diffusion-controlled enzyme kinetics, Langmuir, 10.1021/la010965b, 18, 3, 797-804, 2002.02, This is a follow-up study to our recent reports of lipase catalysis on uniphasic binary monolayers of L-α-dilauroylphosphatidylcholine (DLPC) and cholesterol. The earlier studies were undertaken to show that the reaction kinetics on monolayers of ester hydrolysis catalyzed by an interface active enzyme, lipase, is closely correlated to the lateral dynamics, i.e., the hydrolysis of a lipase substrate is a diffusion-controlled process, whereby the rates were quantitatively analyzed in terms of a theory of purely two-dimensional diffusion-controlled reactions. In so establishing, cholesterol was used as the second component to retard the lateral diffusion coefficient of DLPC to different extents. On the other hand, phospholipids and cholesterol are being found to form "condensed complexes" even in homogeneous monolayers, hence the finding of the diffusion-controlled processes might well be construed to be unique to the phospholipid-cholesterol system. To show that the diffusion-controlled reaction kinetics on monolayers is of more general validity, i.e., not system-specific, we chose a completely different second component to constitute a binary homogeneous monolayer system by which we can vary the lipid diffusion coefficient. The second component is a synthetic polymer, poly(tert-butyl methacrylate) (PtBMA), well-known for its surface activity on the air/water interface, and is demonstrated to form uniphasic monolayers with DLPC at the air/aqueous buffer (pH 7) interface. Upon completing the entire set of measurements for the diffusion coefficients and the hydrolysis rates with the same substrate, umbelliferone stearate, we reached the conclusions that what we found with DLPC/ cholesterol are not unique to the system but equally applicable to DLPC/PtBMA, whereas the polymer is not likely to exert the same sort of retardation effect on monolayer dynamics by specific interactions that result in condensed complexes of phospholipid and cholesterol..
161. Atsushi Takahara, Kensuke Nakamura, Keiji Tanaka, Tisato Kajiyama, Polymer battery R&D in the U.S., Macromolecular Symposia, 10.1002/1521-3900(200010)159:1<229::AID-MASY229>3.0.CO;2-O, 159, 229-245, 2000.12, Polymer electrolytes that have been developed for battery applications fall into two general classes, neat or "pure" polymer and plasticized or gel in which the polymer is combined with a conducting organic electrolyte. The polyethylene oxide (PEO) and its modifications are typical of the "pure" polymer electrolytes. They have poor conductivity at room temperatures, but at elevated temperatures, their conductivity is of the order of 10
-3
to 10
-4
S/cm. The PEO electrolytes have found application in the high temperature (>60°C) lithium metal anode battery systems. The high temperature necessary for good operation makes them unsuitable for use in small consumer appliances. The polymer electrolyte battery development activities have resulted in several high performance battery systems now just entering the market. Not all of the developments have resulted in commercial cell production. The commercialization activities of high performance lithium-ion (Li-Ion) batteries have been based on two general plastic polymer systems: poly-vinylidene difluoride-hexafluoropropylene copolymer (PVdF-HFP) and polyacrylates. The polymer cells are expected to have advantages in manufacturing, flexibility, thin cell formats and lightweight packaging. Important parameters in PVdF gel electrolyte performance include the electrolyte type (combination of organic carbonates), temperature, and HFP copolymer content. Li-Ion coin cells fabricated with a polyolefin separator with either liquid electrolyte or with the PVdF gel polymer electrolyte have equivalent performance..
162. Keiji Tanaka, Yohei Tateishi, Yohei Okada, Toshihiko Nagamura, Masao Doi, Hiroshi Morita, Interfacial mobility of polymers on inorganic solids, Journal of Physical Chemistry B, 10.1021/jp810370f, 113, 14, 4571-4577, 2009.04, The segmental mobility of a typical amorphous polymer, polystyrene, at the interfaces with solid substrates was noninvasively examined by fluorescence lifetime measurements using evanescent wave excitation in conjunction with coarse-grained molecular dynamics simulation. The glass transition temperature (Tg) was discernibly higher at the interface than in the internal bulk region. Measurements at different incident angles of excitation pulses revealed that Tg became higher closer to the interface. The gradient became more marked with an increasing difference in the free energy at the interface between the polymer and solid substrate. The Tg value at the interface decreased with decreasing molecular weight. However, the decrement for the interfacial Tg was not as much as that for the bulk Tg, due to the restriction of chain end portions by the substrate. Finally, it was observed that when a film became thinner than 50 nm, the depressed mobility at the interface coupled with the enhanced mobility induced by the presence of the surface. The experimental and simulation results were in good accord with each other..
163. Atsushi Takahara, Keiji Tanaka, IUMRS-ICA 2008 symposium, sessions X. applications of synchrotron radiation and neutron beam to soft matter science and Y. frontier of polymeric nano-soft-materials - Precision polymer synthesis, self-assembling and their functionalization, Journal of Physics: Conference Series, 10.1088/1742-6596/184/1/011001, 184, 2009.01, Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science (Symposium X of IUMRS-ICA2008) Toshiji Kanaya, Kohji Tashiro, Kazuo Sakura Keiji Tanaka, Sono Sasaki, Naoya Torikai, Moonhor Ree, Kookheon Char, Charles C Han, Atsushi Takahara This volume contains peer-reviewed invited and contributed papers that were presented in Symposium X Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science at the IUMRS International Conference in Asia 2008 (IUMRS-ICA 2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. Structure analyses of soft materials based on synchrotron radiation (SR) and neutron beam have been developed steadily. Small-angle scattering and wide-angle diffraction techniques clarified the higher-order structure as well as time dependence of structure development such as crystallization and microphase-separation. On the other hand, reflectivity, grazing-incidence scattering and diffraction techniques revealed the surface and interface structural features of soft materials. From the viewpoint of strong interests on the development of SR and neutron beam techniques for soft materials, the objective of this symposium is to provide an interdisciplinary forum for the discussion of recent advances in research, development, and applications of SR and neutron beams to soft matter science. In this symposium, 21 oral papers containing 16 invited papers and 14 poster papers from China, India, Korea, Taiwan, and Japan were presented during the three-day symposium. As a result of the review of poster and oral presentations of young scientists by symposium chairs, Dr Kummetha Raghunatha Reddy (Toyota Technological Institute) received the IUMRS-ICA 2008 Young Researcher Award. We are grateful to all invited speakers and many participants for valuable contributions and active discussions. Organizing committee of Symposium (IUMRS-ICA 2008) Professor Toshiji Kanaya (Kyoto University) Professor Kohji Tashiro (Toyota Technological Institute) Professor Kazuo Sakurai(Kitakyushu University) Professor Keiji Tanaka (Kyushu University) Dr Sono Sasaki (JASRI/Spring-8) Professor Naoya Torikai (KENS) Professor Moonhor Ree (POSTECH) Professor Kookheon Char (Seoul National University) Professor Charles C Han (CAS) Professor Atsushi Takahara(Kyushu University) Frontier of Polymeric Nano-Soft-Materials, Precision Polymer Synthesis, Self-assembling and Their Functionalization (Symposium Y of IUMRS-ICA2008) Seiichi Kawahara, Rong-Ming Ho, Hiroshi Jinnai, Masami Kamigaito, Takashi Miyata, Hiroshi Morita, Hideyuki Otsuka, Daewon Sohn, Keiji Tanaka It is our great pleasure and honor to publish peer-reviewed papers, presented in Symposium Y Frontier of Polymeric Nano-Soft-Materials Precision Polymer Synthesis, Self-assembling and Their Functionalization at the International Union of Materials Research Societies International Conference in Asia 2008 (IUMRS-ICA2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. Polymeric nano-soft-materials are novel outcomes based on a recent innovative evolution in polymer science, i.e. precision polymer synthesis, self-assembling and functionalization of multi-component systems. The materials are expected to exhibit specific functions and unique properties due to their hierarchic morphologies brought either by naturally-generated ordering or by artificial manipulation of the systems, e.g., crystallization and phase-separation. The emerging precision synthesis has brought out new types of polymers with well-controlled primary structures. Furthermore, the surface and interface of the material are recognized to play an important role in the outstanding mechanical, electrical and optical properties, which are required for medical and engineering applications. In order to understand structure-property relationships in the nano-soft-materials, it is indispensable to develop novel characterization techniques. Symposium Y aimed to provide recent advances in polymer synthesis, self-assembling processes and morphologies, and functionalization of nano-soft-materials in order to initiate mutual and collaborative research interest that is essential to develop revolutionarily new nano-soft-materials in the decades ahead. Four Keynote lectures, 15 invited talks and 30 posters presented important new discoveries in polymeric nano-soft-materials, precision polymer synthesis, self-assembling and their functionalization. As for the precision polymer synthesis, the latest results were provided for studies on synthesis of polyrotaxane with movable graft chains, organic-inorganic hybridization of polymers, supra-molecular coordination assembly of conjugated polymers, precision polymerization of adamantane-containing monomers, production of high density polymer brush and synthesis of rod coil type polymer. The state-of-the-art results were introduced for the formation of nano-helical-structure of block copolymer containing asymmetric carbon atoms, self-assembling of block copolymers under the electric field, self-assembling of liquid crystalline elastomers, preparation of nano cylinder template films and mesoscopic simulation of phase transition of polymers and so forth. Moreover, recent advantages of three-dimensional electron microtomography and scanning force microscopy were proposed for analyses of nano-structures and properties of polymeric multi-component systems. Syntheses, properties and functions of slide-ring-gel, organic-inorganic hybrid hydrogels, hydrogel nano-particles, liquid-crystalline gels, the self-oscillating gels, and double network gels attracted participants' attention. Modifications of naturally occurring polymeric materials with supercritical carbon dioxide were introduced as a novel technology. Some of the attractive topics are presented in this issue. We are grateful to all the speakers and participants for valuable contributions and active discussions. Organizing committee of Symposium Y (IUMRS-ICA 2008) Chair Seiichi Kawahara (Nagaoka University of Technology, Japan) Vice Chairs Rong-Ming Ho (National Tsing Hua University, Taiwan) Hiroshi Jinnai (Kyoto Institute of Technology, Japan) Masami Kamigaito (Nagoya University, Japan) Takashi Miyata (Kansai University, Japan) Hiroshi Morita (National Institute of Advanced Industrial Science and Technology, Japan) Hideyuki Otsuka (Kyushu University, Japan) Daewon Sohn (Hanyang University, Korea) Keiji Tanaka (Kyushu University, Japan).
164. Fumi Ariura, Keiji Tanaka, Toshihiko Nagamura, Michel Schappacher, Redouane Borsali, Alain Deffieux, Investigations of bulk properties of comb polystyrene, 235th ACS National Meeting, Spring 2008 American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 49, 1, 52-53, 2008.09.
165. Daisuke Kawaguchi, Atsushi Takano, Yushu Matsushita, Keiji Tanaka, Toshihiko Nagamura, Naoya Torikai, Interdiffusion of cyclic polystyrene whose molecular weight is larger than the critical entanglement molecular weight, Nihon Reoroji Gakkaishi, 10.1678/rheology.36.113, 36, 2, 113-115, 2008.07, Interdiffusion of cyclic polystyrene (c-hPS) / cyclic deuterated polystyrene (c-dPS) laminated film whose molecular weights are ca.50 k was examined by neutron reflectivity and dynamic secondary ion mass spectroscopy. It has been found that time evolution of the interfacial thicknesses of (c-hPS/c-dPS) multi-layer films are similar to those of the corresponding linear hPS/linear dPS (l-hPS/l-dPS) bilayer films at short time region. However, at the annealing time longer than 5×103 s, the interfacial thicknesses of (c-hPS/c-dPS) multi-layer films are evidently larger than those of the (l-hPS/l-dPS) films at each observing time. These results can be explained in terms of the less entanglement nature of cyclic polymers than that of the linear ones..
166. Kei Ichi Akabori, Keiji Tanaka, Hiroki Murase, Atsushi Takahara, Tisato Kajiyama, Model analysis of scanning viscoelasticity microscopy and its applications to polymer surfaces, Nihon Reoroji Gakkaishi, 10.1678/rheology.36.87, 36, 2, 87-92, 2008.07, Scanning viscoelasticity microscopy (SVM) with a mechanical model analysis was applied to polystyrene (PS) surfaces. When the surface was in a glassy state, that is, in an elastic regime, the SVM vibrational system can be simply expressed by a series model composed of two springs such as a cantilever and the sample surface. Once the surface reaches in a viscoelastic regime, a damping factor must be incorporated into the model surface. The spring constants for the PS surfaces being in glassy and transition states were successfully extracted by the analysis. The surface value even for the glassy state was lower than the corresponding bulk value by a few decades..
167. Keiji Tanaka, Noriaki Sanada, Masaya Hikita, Tetsuya Nakamura, Tisato Kajiyama, Atsushi Takahara, Surface depth analysis for fluorinated block copolymer films by X-ray photoelectron spectroscopy using C 60 cluster ion beam, Applied Surface Science, 10.1016/j.apsusc.2008.02.089, 254, 17, 5435-5438, 2008.06, X-ray photoelectron spectroscopy (XPS) using fullerene (C 60 ) cluster ion bombardment was applied to films of a fluorinated block copolymer. Spectra so obtained were essentially different from those using Ar ion beam. Structure in the surface region with the depth down to 60 nm drawn on the basis of XPS with C 60 beam was essentially the same as the one drawn by the result using dynamic secondary ion mass spectrometry, which is a well-established method for the depth analysis of polymers. This implies that XPS using C 60 beam enables one to gain access to the depth analysis of structure in polymer films with the depth range over the analytical depth of conventional XPS, that is, three times inelastic mean-free path of photoelectrons..
168. Yoshihisa Fujii, Hironori Atarashi, Toshihiko Nagamura, Keiji Tanaka, Entanglement effect on film retention of poly(methyl methacrylate) in methanol, Chemistry Letters, 10.1246/cl.2008.326, 37, 3, 326-327, 2008.03, Morphology for films of poly(methyl methacrylate) with various molecular weights was observed before and after methanol immersion by using atomic force microscopy so that the effect of chain entanglement on film retention of a polymer in a liquid can be discussed..
169. Ifu Narayama, Daisuke Baba, Atsushi Takahara, Keiji Tanaka, Direct observation of surface and internal phase-separated structure of the active layer buried in organic photovoltaic cells, Applied Surface Science, 10.1016/j.apsusc.2010.07.093, 257, 3, 1145-1148, 2010.11, A phase-separated structure of the active layer, of variable thickness, buried in organic thin film solar cells (OTSC) was directly observed by scanning force microscopy (SFM) with the aid of a surface and interface cutting analysis system (SAICAS). This deals with SFM observation to both the surface and the internal regions of the OTSCs, leading to discussion about the formation of the overlayer in the active layer..
170. Ayanobu Horinouchi, Yoshihisa Fujii, Norifumi L. Yamada, Keiji Tanaka, Surface reorganization of thin poly(methyl methacrylate) films induced by water, Chemistry Letters, 10.1246/cl.2010.810, 39, 8, 810-811, 2010.07, Neutron reflectivity revealed that the surface aggregation states of poly(methyl methacrylate) film can be altered by water, which is a typical nonsolvent, in a relatively large scale..
171. Yohei Tateishi, Naoki Kai, Hidenori Noguchi, Kohei Uosaki, Toshihiko Nagamura, Keiji Tanaka, Local conformation of poly(methyl methacrylate) at nitrogen and water interfaces, Polymer Chemistry, 10.1039/b9py00227h, 1, 3, 303-311, 2010.05, The local conformation of poly(methyl methacrylate) (PMMA) chains at the nitrogen (N2) and water interfaces was studied by infrared-visible sum-frequency generation (SFG) spectroscopy. Although SFG spectra in the C-H region for PMMA at the N2 interface have been hitherto reported, the peak assignments are not in accord with one another. Thus, we first made accurate assignments of SFG peaks using films, which had been well annealed at a temperature above the glass transition temperature for a long time, of three different deuterated PMMAs as well as normal protonated PMMA. At the N 2 interface, hydrophobic functional groups such as α methyl, ester methyl and methylene groups were present. While the α methyl group was oriented along the direction parallel to the interface, ester methyl and methylene groups were oriented normal to the interface. Quantitative discussion concerning the orientation of the functional groups of PMMA at the N2 interface was aided by a model calculation. Once the PMMA film contacted water, the carbonyl groups of the PMMA side chains were oriented to the water phase to form hydrogen bonds with water molecules, resulting in the migration of ester methyl into the internal region of the film. Concurrently, the methylene groups became randomly oriented at the water interface and/or in part migrated into the internal region. Interestingly, the α methyl groups still existed at the water interface oriented along the parallel direction. The outermost region of PMMA in water can consist of hydrophilic and hydrophobic domains with sub-nanometre scale. Water molecules H-bond to themselves near the hydrophobic domains, leading to the formation of an ice-like structure of water molecules. However, water molecules adjacent to the hydrophilic domains H-bond with carbonyl groups..
172. Hiroyuki Michishita, Kei Ichi Akabori, Keiji Tanaka, Hiroshi Matsumoto, Daizou Haruta, Yoshinori Nagata, Nagaaki Yamamoto, Tatsumi Ishihara, Effects of pressure on stability of nafion membrane under water electrolysis, Electrochemistry, 10.5796/electrochemistry.78.42, 78, 1, 42-49, 2010.01, In previous study, proton conductivity increased with increasing pressure under water electrolysis, so the effects of pressure on the stability of Nafion 117 have been studied. It was found that conductivity of Nafion 117 drastically decreased at initial few h and then gradually decreased in the following period under electrolysis condition. Decrease in conductivity can be explained by decomposition of Nafion 117. Decomposition of Nafion 117 is accelerated by increasing pressure. Solid state NMR, IR, and Raman spectroscopy suggested that the electrochemical oxidation of sulfo group was occurred at initial period followed by decomposition of CFn main or side chain. Therefore, initial increase in resistance can be explained by desorption of sulfo group in Nafion 117. Desorption of sulfo group also forms pin hole in Nafion membrane which may cause gas leakage under water electrolysis. Mechanical strength of Nafion membrane is also drastically decreased at initial electrolysis period. Consequently, chemical stability of Nafion 117 may cause serious problem for water electrolysis application and this study reveals that increasing pressure strongly accelerates the decomposition of Nafion 117..
173. Kei ichi Akabori, Hironori Atarashi, Masaaki Ozawa, Tetsuo Kondo, Toshihiko Nagamura, Keiji Tanaka, Glass transition behavior of hyper-branched polystyrenes, polymer, 10.1016/j.polymer.2009.08.029, 50, 20, 4868-4875, 2009.09, Hyper-branched polystyrenes (HBPS) were synthesized. The bulk glass transition temperature (Tg) measured by differential scanning calorimetry (DSC) for two kinds of HBPS with an equivalent Mw, which were fractionated from different lots, were different, being respectively higher and lower than that of the corresponding linear polystyrene (PS). Infrared spectroscopy revealed that the Tg of HBPS increased with an increasing extent of intramolecular cross-linking, or cyclization, in the molecule. The segmental dynamics of HBPS was examined by dynamic mechanical analysis. The relaxation temperature for the segmental motion in HBPS was consistent with the DSC results. The fragility index was always lower for HBPS than for the linear PS, regardless of its primary structure and chain end chemistry. This would indicate that the segmental motion for HBPS is less cooperative than that of the linear PS, probably due to a lack of intermolecular chain entanglements in HBPS..
174. Yoshihisa Fujii, Hironori Atarashi, Masahiro Hino, Toshihiko Nagamura, Keiji Tanaka, Interfacial width in polymer bilayer films prepared by double-spin-coating and flotation methods, ACS Applied Materials and Interfaces, 10.1021/am9004336, 1, 9, 1856-1859, 2009.09, A spin-coating method with the aid of selective solvents has been used to construct multilayer structures for organic devices under the assumption that the solvents do not invade a preformed structure. To confirm the assumption, we examined the interfacial width (?i) of model polymer bilayers, composed of polystyrene and perdeuterated poly(methyl methacrylate), prepared by spin-coating and flotation methods. Neutron reflectivity measurements revealed that the ?i value was larger for the spin-coating method than for the flotation method. These results cast doubt on the validity of the assumption. This knowledge should be kept in mind when this method is applied to construct multilayer structures..
175. David P. Penaloza, Koichiro Hori, Atsuomi Shundo, Keiji Tanaka, Spatial heterogeneity in a lyotropic liquid crystal with hexagonal phase, Physical Chemistry Chemical Physics, 10.1039/c2cp40284j, 14, 15, 5247-5250, 2012.04, Non-ionic surfactant hexaethylene glycol, C 12E 6, in water self-assembles into various kinds of mesophases by varying the surfactant concentration. A spatial heterogeneity was discussed on the basis of the diffusion of probe particles dispersed in the C 12E 6-water solution. Interestingly, at 50 wt% C 12E 6 where the hexagonal structure was formed, two kinds of motion of probe particles were observed: some particles normally diffused while others were restricted, indicating the existence of a heterogeneity in the physical properties. Such heterogeneity can be explained in terms of heterogeneous structures composed of hexagonal domains with isotropic-like regions..
176. Hirofumi Tsuruta, Yoshihisa Fujii, Keiji Tanaka, One-pot surface modification of rubbery polymer films, Polymer Chemistry, 10.1039/c1py00488c, 3, 2, 319-321, 2012.02, A novel method to modify the surface of rubbery polymer films on the basis of the preferential segregation of inorganic materials fed into the system in tiny amounts is proposed. The surface so prepared had several prominent properties such as surface hardness, anti-oxidant properties, transparency, and so forth..
177. Koichiro Hori, Hisao Matsuno, Keiji Tanaka, Sorption kinetics of methanol in thin poly(methyl methacrylate) films studied by optical reflectivity, Soft Matter, 10.1039/c1sm06098h, 7, 21, 10319-10326, 2011.11, To study the thickness dependence of methanol diffusion into poly(methyl methacrylate) (PMMA) films, an experimental method based on optical reflectivity was proposed. The method can cover a thickness range from the micrometre down to the nanometre scale using a single set-up. Methanol molecules diffuse into PMMA following a Case II mechanism in which they induce segmental motion of the matrix polymer. We observed two diffusion modes, fast and slow, assignable respectively to the outermost layer and the remaining internal region including the substrate interface. When the film becomes thinner, the ratio of the interfacial area to the total volume increases. This results in slowing down of the methanol diffusion due to the contribution of the depressed segmental mobility at the substrate interface. Interestingly, the thickness of the mobility-enhanced layer at the outermost region of the film similarly decreased with decreasing total thickness owing to the effect of the substrate interface..
178. Hironori Atarashi, Yoshihisa Fujii, Dai Yamazaki, Masahiro Hino, Hiroshi Morita, Keiji Tanaka, Density distributions of poly (methyl methacrylate) thin films in non-solvents, Kobunshi Ronbunshu, 10.1295/koron.68.608, 68, 9, 608-615, 2011.09, Recently, polymeric materials nave oeen widely used in applications sucn as medical materiais, in tnese applications, the surrace comes into contact with a different phase. Thus, their interfaces should be studied, both their structures as well as their dynamics. The density profiles of a perdeuterated poly(methyl methacrylate) (dPMMA) film in water, hexane, methanol, ethanol, 1-propanol, and 1-butanol were examined along the direction normal to the interface by neutron reflectivity (NR). Although these liquids are typical non-solvents for dPMMA, the liquid/polymer interfaces were diffuse in comparison with the air/polymer interface probably due to the partial dissolution of polymer segments at the outermost region of the film. Interestingly, in water, an anomalous swollen layer was formed beneath the diffused interface. On the other hand, such a swollen layer was not observed for the dPMMA films in alcohols. This is simply because alcohol molecules deeply penetrated into the films. The amounts of the alcohols penetrated are related to the interaction parameter. The fractional amount of nonsolvents at the substrate interface was higher than that in the internal region of the film..
179. Keiji Tanaka, Yoshihisa Fujii, Polymer structure and physical properties at non-solvent interfaces, Kobunshi, 60, 3, 148-152, 2011.03, Interfaces of polymers with "non-solvents" play an important role in their functional properties such as wettability, friction with lubricants, cell adhesion, and biocompatibility. To design and construct highly functionalized polymers for applications that exploit these characteristics, aggregation states of the polymers at the liquid interfaces must be understood as the first benchmark. However, this is experimentally difficult because such interfaces are buried. In this review, we introduce recent development of the issue with the advent of modem experimental techniques..
180. Toyoaki Hirata, Hisao Matsuno, Masaru Tanaka, Keiji Tanaka, Surface segregation of poly(2-methoxyethyl acrylate) in a mixture with poly(methyl methacrylate), Physical Chemistry Chemical Physics, 10.1039/c0cp02101f, 13, 11, 4928-4934, 2011.03, Poly(2-methoxyethyl acrylate) (PMEA) exhibits excellent blood compatibility. To understand why such a surface functionality exists, the surface of PMEA should be characterized in detail, structurally and dynamically, under not only ambient conditions, but also in water. However, a thin film of PMEA supported on a solid substrate can be easily broken, namely it is dewetted. Our strategy to overcome this difficulty is to mix PMEA with poly(methyl methacrylate) (PMMA). Differential scanning calorimetry and cloud point measurements revealed that the PMEA/PMMA blend has a phase diagram with a lower critical solution temperature. The blend surface was also characterized by X-ray photoelectron spectroscopy in conjunction with microscopic observations. Although PMEA is preferentially segregated over PMMA at the blend surface due to its lower surface free energy, the extent of segregation in the as-prepared films was not sufficient to cover the surface. Annealing the blend film at an appropriate temperature, higher than the glass transition temperature and lower than the phase-separation temperature of the blend, enabled us to prepare a stable and flat surface that was perfectly covered with PMEA..
181. Takako Kikuchi, Yoshito Ohtake, Kazumi Nakayama, Masayuki Hori, Keiji Tanaka, Development of a method to identify recycled polycarbonate, KOBUNSHI RONBUNSHU, 10.1295/koron.68.731, 68, 11, 731-736, 2011.01, To encourage the recycling of materials, the government provides subsidizes for manufacturers which use recycled materials to process final products. Unfortunately, this causes a camouflage of recycled-content products. Hence, a method to judge whether the material is truly made of previously used source needs to be established. In this study, we focus on recycled plastics, especially, polycarbonate (PC). Plastics are thermally and mechanically damaged during its molding process and practical use. This leads to faster degradation of recycled plastics than the corresponding pristine ones. We here propose how we can identify recycled PC taking into account the degradation kinetics..
182. Hisao Matsuno, Jun Ichi Nakahara, Keiji Tanaka, Dynamic mechanical properties of solid films of deoxyribonucleic acid, Biomacromolecules, 10.1021/bm1010933, 12, 1, 173-178, 2011.01, Solid films of deoxyribonucleic acid (DNA) from salmon testes were prepared by a solvent-casting method. The thermal molecular motion of the DNA film was examined by dynamic mechanical analysis (DMA). Four absorption peaks and one shoulder of the loss modulus were observed in the temperature domain from approximately 150 to 490 K. To assign these, thermal analysis employing thermogravimetry (TG) and differential thermal analysis (DTA) was used in conjunction with ultraviolet (UV)-visible and Fourier-transform infrared (FT-IR) spectroscopy. It seems most likely that, in order of increasing temperature, they are a BI→BII conformational transition, a relatively large-scale movement associated with water molecules, water evaporation, thermal denaturation of DNA, and a glass transition..
183. Atsuomi Shundo, Keiji Tanaka, Mesoscopic heterogeneity in supramolecular network systems, Nihon Reoroji Gakkaishi, 10.1678/rheology.42.89, 42, 2, 89-95, 2014.01, Molecules are often assembled by themselves with a large aspect ratio, leading to the formation of network structure based on their entanglements. Such systems, so-called "supramolecular network systems" possess hierarchical structure with various length scales ranging from nanometer to micrometer. Thus, to give a better understanding of dynamics for the supramolecular network systems, it is necessary to examine the structure and physical properties at various length scales, and clarify the correlation. By using optical tweezers and particle tracking techniques, we here show the local rheological properties in a worm-like micelle solution and a supramolecular hydrogel, which are formed by the networks based on the self-assembly of the amphiphilic molecules in water. In these techniques, viscoelastic information can be accessed on the basis of the movement of probe particles dispersed in a sample to be measured. For the worm-like micelle solution, we found that the viscoelastic functions (G′ and G″ ) varied depending on the location measured and the location-dependent variation of G′ and G″ was observed only at the measurement timescale being shorter than the relaxation time. This can be understood by taking into account that there exists a concentration fluctuation in the solution. Such fluctuation can be regard as a spatial heterogeneity when one takes a snapshot of the solution at a time shorter than the relaxation time. Also, the heterogeneity in the rheological properties was observed in a sol obtained by physically disrupting the supramolecular hydrogel. The extent of the heterogeneity decreased as a solto-gel transition proceeded. Such homogenization was associated with the change in the network structure rather than that in the molecular assembled state, which remains comparable in the sol and gel..
184. Ayanobu Horinouchi, Yoshihisa Fujii, Keiji Tanaka, Interfacial dynamics of poly(methyl methacrylate) in water, 4th International Symposium on Slow Dynamics in Complex Systems: Keep Going Tohoku 4th International Symposium on Slow Dynamics in Complex Systems Keep Going Tohoku, 10.1063/1.4794616, 1518, 459-461, 2013.03, Aggregation states of polymers at the surface generally tend to alter to their most stable ones in response to their surrounding environment. We here apply a time-resolved contact angle measurement to examine the rate of the surface reorganization of poly(methyl methacrylate) (PMMA) in water. By doing these measurements at various temperatures, it is possible to extract the apparent activation energy of the surface dynamics based on the relation of the surface relaxation time and temperature. Also, sum-frequency generation spectroscopy revealed that the surface reorganization involves the conformational changes in the main chain portion as well as the side chains. Hence, the dynamics observed here might reflect the segmental motion at the outermost region of the PMMA film, in which water plays as a plasticizer..
185. Hirofumi Tsuruta, Yoshihisa Fujii, Masao Doi, Hiroshi Morita, Keiji Tanaka, Relaxation of polystyrene at interface with solid substrate, 4th International Symposium on Slow Dynamics in Complex Systems: Keep Going Tohoku 4th International Symposium on Slow Dynamics in Complex Systems Keep Going Tohoku, 10.1063/1.4794617, 462-465, 2013.03, The local conformation of polymer chains in a film at the interface with a substrate was studied by sumfrequency generation spectroscopy. When a polystyrene (PS) film was prepared on a quartz substrate by a spin-coating method, the chains were aligned in the interfacial plane of the substrate. This interfacial orientation of chains was not observed for a PS film prepared by a solvent-casting method. The local conformation of chains at the substrate interface was interestingly unchanged even at a temperature that was 80 K higher than the bulk glass transition temperature. This observation indicates that polymer chains at the substrate interface can be only partially relaxed under conditions where the bulk chains are fully relaxed. On the other hand, interfacial chains could be easily relaxed by the solvent annealing..
186. Yoshihisa Fujii, Hiroshi Morita, Atsushi Takahara, Keiji Tanaka, Mobility gradient of polystyrene in films supported on solid substrates, Glass Transition, Dynamics and Heterogeneity of Polymer Thin Films, 10.1007/12_2012_175, 1-28, 2013.01, In this review, we show the distribution of glass transition temperature (T g) in monodisperse polystyrene (PS) films coated on silicon oxide layers along the direction normal to the surface. Scanning force microscopy with a lateral force mode revealed that surface T g () was lower than the corresponding bulk T g (). Interestingly, the glass transition dynamics at the surface was better expressed by an Arrhenius equation than by a Vogel-Fulcher-Tamman equation. Interdiffusion experiments for PS bilayers at various temperatures, above and below, enabled us to gain direct access to the mobility gradient in the surface region. T g at the solid substrate was examined by fluorescence lifetime measurements using evanescent wave excitation. The interfacial T g was higher than the corresponding. The extent of the elevation was a function of the distance from the substrate and the interfacial energy. The T g both at the surface and interface was also studied by the coarse-grained molecular dynamics simulation. The results were in good accordance with the experimental results. Finally, dynamic mechanical analysis for PS in thin and ultrathin films was made. The relaxation time for the segmental motion became broader towards the faster and slower sides, due probably to the surface and interfacial mobility. Graphical Abstract:.
187. Daisuke Kawaguchi, Keiji Tanaka, Structures and physical properties at surfaces and interfaces of polymers, Toraibarojisuto/Journal of Japanese Society of Tribologists, 58, 10, 742-749, 2013.
188. Tomoyasu Hirai, Kaoru Kawasaki, Keiji Tanaka, Interfacial kinetics of a model epoxy-amine addition reaction, Physical Chemistry Chemical Physics, 10.1039/c2cp42673k, 14, 39, 13532-13534, 2012.10, The kinetics of the addition reaction at a solid interface for a model epoxy-amine system composed of monofunctionalized phenyl glycidyl ether and hexylamine was examined. The chemical character for the reaction of this system at the interface was the same as that in the bulk, while the physical nature was significantly different. Slowing down of the diffusion for the reactants in close proximity to the solid interface was also addressed by interfacial selective spectroscopy..
189. Yoshihisa Fujii, Keiji Tanaka, Thermal molecular motion of poly(methyl methacrylate) at various interfaces, Nihon Reoroji Gakkaishi, 10.1678/rheology.40.143, 40, 3, 143-149, 2012.10, Thermal molecular motion of poly(methyl methacrylate) (PMMA) at various interfaces, gases and liquids, was discussed. The α a- and β-relaxation processes were clearly observed even at the air interface. Both relaxation temperatures at the air interface were lower than the corresponding ones in the bulk. In addition, the extent to which the peak temperature for the surface relaxation processes fell below that of the bulk strongly depended on the stereoregularity of the films. Then, thermal molecular motion of PMMA was analyzed at gaseous carbon dioxide (CO 2) interface. It was more enhanced than that at gaseous nitrogen interface because CO 2 molecules were sorbed in the interfacial region, which played as plasticizing agents. Finally, mechanical properties of PMMA were also studied at interfaces with liquids such as water, hexane and methanol. The modulus decreased closer to the outermost region of the film. The extent to which the modulus decreased in the interfacial region was consistent with the amount of liquid sorbed into the film. Therefore, it can be claimed that interfacial molecular motion of polymers can be regulated on the basis of the aggregation states..
190. Kenji Okamoto, Tatsuya Ganbe, Nobuyuki Sekine, Mika Aoki, Manabu Inutsuka, Atsuomi Shundo, Daisuke Kawaguchi, Keiji Tanaka, Nanoscale characterization of epoxy interface on silica, 1st IEEE International Conference on Dielectrics, ICD 2016 Proceedings of the 2016 IEEE International Conference on Dielectrics, ICD 2016, 10.1109/ICD.2016.7547549, 1, 84-87, 2016.08, The objective of this study is to carry out nanoscale characterization of the epoxy resin interface on silica by determining the glass-transition temperature (Tg) and molecular conformation at the interface by means of a novel non-destructive method. The Tg was determined by fluorescence lifetime measurements using evanescent wave excitation. It was revealed that the Tg of epoxy resin at a distance of 30 nm from the interface was 10 K higher than that at a distance of 80 nm. The chemical composition and molecular conformation were analysed by X-ray photoelectron spectroscopy and sum-frequency generation (SFG) spectroscopy, respectively. The SFG data revealed that unreacted epoxy group remained at the interface. The Tg of epoxy resin increased in the regions near the interface, and the epoxy group remained unreacted at a distance of ca. 10 nm or less from the interface..
191. Yukari Oda, Cui Zhang, Daisuke Kawaguchi, Hisao Matsuno, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Bio-Inert Surfaces
Design of Blood-Compatible Interfaces with Poly(vinyl ether)s (Adv. Mater. Interfaces 12/2016), Advanced Materials Interfaces, 10.1002/admi.201670058, 3, 12, 2016.06.
192. Keiji Tanaka, Takeshi Serizawa, Wen Chang Chen, Kookheon Char, Takashi Kato, Special Issue
Polymer surfaces, interfaces and thin films, Polymer Journal, 10.1038/pj.2016.26, 48, 4, 2016.04.
193. Tomoyasu Hirai, Yukari Oda, David P. Penaloza, Daisuke Kawaguchi, Keiji Tanaka, Control of surface structure and dynamics of polymers based on precision synthesis, Anionic Polymerization Principles, Practice, Strength, Consequences and Applications, 10.1007/978-4-431-54186-8_19, 861-880, 2015.09, Aggregation states and dynamics of polymers at the surface are generally different from those in the corresponding bulk state. To what extent they differ from that of the bulk strongly depends on the polymer primary structure. Therefore, finetuning the surface properties of polymers can be achieved by exhibiting control over their structure using precision polymer synthesis. We here show how the polymer design effectively impacts the structure and dynamics at the surfaces..
194. Dong Ha Kim, Keiji Tanaka, Juan Peng, A special issue on functional polymeric nanomaterials, Science of Advanced Materials, 10.1166/sam.2015.2274, 7, 5, 827-829, 2015.01.
195. Yukari Oda, Daisuke Kawaguchi, Toyoaki Hirata, Norifumi L. Yamada, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Density profiles of well-defined poly(methyl 2-propenyl ether) (PMPE) near water interface, Macromolecular Symposia, 10.1002/masy.201400031, 350, 1, 99-104, 2015.01, Poly(methyl 2-propenyl ether) (PMPE) is structually different in terms of the presence of an α-methyl group on the main chain from poly(vinyl methyl ether) (PVME), the phase behaviors of which have been widely characterized with polystyrene (PS) and water. Due to the incorporation of the α-methyl group, PMPE is immiscible with both PS and water. These results encouraged us to investigate a PMPE/water interface more closely. Thus, the density profiles of PMPE in the vicinity of the water interface were probed by neutron reflectivity (NR) measurement. Even in the presence of the α-methyl group on the main chain, PMPE slightly swelled near the water interface. The obtained results will give us an insight into a better design and construction of the polymers for several bioapplications..
196. Takaaki Date, Yuko Ueda, Hironori Atarashi, Toshiki Sawada, Hideyo Matsuzawa, Keiji Tanaka, Takeshi Serizawa, Difference in protein adsorption onto polymer films with or without thermal annealing, Journal of Nanoscience and Nanotechnology, 10.1166/jnn.2014.8580, 14, 4, 3106-3111, 2014.04, Protein adsorptions onto non-annealed (NA) and thermally annealed (TA) polyetherimide films were examined by surface plasmon resonance measurements. Proteins adsorbed onto the NA films with smaller adsorption constants in comparison with the TA films. Neutron reflectivity measurements of the two films suggested that the outermost region of the NA films swelled with larger amounts of water molecules than the TA films. It is plausible that the aforementioned difference in the protein adsorption properties is derived from the difference in the interfacial aggregation structures of the two films..
197. Yukari Oda, Keiji Tanaka, Aggregation states and molecular motion of well-defined vinyl polymers at the water interface, KOBUNSHI RONBUNSHU, 10.1295/koron.71.343, 71, 8, 343-351, 2014.01, We investigated the conformation of PMMA in thin films at the air-water interface by sum frequency generation (SFG) spectroscopy and discuss the effect of stereoregularity on the interfacial structure of PMMA. At the air interface, isotactic PMMA takes a helical conformation where the hydrophilic carbonyl groups are oriented towards the interfacial region of the film. Thus, even though the polymer chains come in contact with water, the chain conformation at the interface changes very little. The structure of syndiotactic PMMA at the air and water interfaces is significantly different. Poly(methyl 2-propenyl ether) (PMPE), synthesized via living cationic polymerization, is structurally similar to PMMA, but it lacks the carbonyl group. We discuss the effect of the carbonyl group on the water structure at the interface by comparing the results of our measurements to the previously reported PMMA-water system. This knowledge is crucial for the design and construction of highly-functionalized polymer interfaces for biological applications..
198. Yongming Hong, Yawei Li, Fengliang Wang, Biao Zuo, Xinping Wang, Li Zhang, Daisuke Kawaguchi, Keiji Tanaka, Enhanced Thermal Stability of Polystyrene by Interfacial Noncovalent Interactions, Macromolecules, 10.1021/acs.macromol.8b01012, 51, 15, 5620-5627, 2018.08, The local conformation of polystyrene (PS) and deuterated PS at the interface with quartz substrates, which were covered with phenyl groups using phenyltrimethoxysilane (PTS) under various conditions, was examined by sum frequency generation spectroscopy. As evidenced by the red-shift of the wavenumber of the v
2
vibration mode for phenyl groups, it was claimed that PTS phenyl groups standing vertically from the quartz surface induced the perpendicular orientation of PS phenyl rings by energetically favorable parallel-displaced π-π interactions at the interface. The local conformation of PS chains strongly anchored onto the substrate by the π-π interactions remained almost unchanged for 48 h even at a temperature 60 K higher than the bulk glass transition temperature. That is, the interfacial π-π interactions facilitated the adsorption of PS chains on the substrate to attain a large enthalpic gain, resulting in significantly slower dynamics of PS chains at the interface. Our results illustrate the importance of the interfacial noncovalent interactions in controlling the structure and dynamics of macromolecular chains at the interface as well as in the thin film geometry..
199. Yuji Matsumoto, Atsuomi Shundo, Masashi Ohno, Nobutomo Tsuruzoe, Masahiro Goto, Keiji Tanaka, Mesoscopic Heterogeneity in Pore Size of Supramolecular Networks, Langmuir, 10.1021/acs.langmuir.8b00641, 34, 25, 7503-7508, 2018.06, There has been a considerable interest in developing new types of gels based on a network of fibrous aggregate composed of low molecular weight gelators, also known as supramolecular gels (SMGs). Unlike conventional polymer gels with chemical cross-linking, the network formation in SMGs does not involve any covalent bonds. Thus, the network in SMGs has been often regarded as homogenous or less heterogeneous in comparison with that in chemically cross-linked polymer gels. In this study, we have experimentally verified the existence of the network heterogeneity even in SMGs. The thermal motion of probe particles in SMGs, which were prepared from aqueous dispersions of gelators having a different number of peptide residues, PalGH, PalG2H, and PalG3H, was tracked. The gels were spatially heterogeneous in terms of the network pore size, as evidenced by the variation in the particle motion depending on the location, at which a particle existed. With varying particle size, it was found that the characteristic length scale of the heterogeneity was in the order of (sub)micrometers and was smaller in the order of the PalG2H, PalG3H, and PalGH gels..
200. Keiji Tanaka, Aggregation states and thermal molecular motion of polymer chains at solid interfaces, Journal of Fiber Science and Technology, 10.2115/fiber.74.P-6, 74, 1, P6-P9, 2018.01.
201. Atsuomi Shundo, Takuya Yamamoto, Yasuyuki Tezuka, Keiji Tanaka, Load-induced frictional transition for well-defined cyclic self-Assembled monolayers, Toraibarojisuto/Journal of Japanese Society of Tribologists, 63, 4, 248-252, 2018.01, Self-Assembled monolayer (SAM) with amphiphilic linear molecules has been studied as a surface modifier. In general, the surface properties of a SAM are dependent on the chain end chemistry of the molecules. Thus, a SAM composed of alkane loops from cyclic alkanedisulfide on a gold substrate, in which both sulfurs arc bound to gold, may possess unique surface properties due to the chain folding as well as a lack of chain ends. We here focus on the frictional properties of the linear and cyclic SAMs. For the cyclic SAM, the load dependence of the frictional force became more striking beyond a threshold. Such a frictional transition was not observed for the corresponding linear SAM. The load-induced transition in the frictional response from the alkane loops could be related to the conformational change of the alkane loops, which collapsed along the direction normal to the SAM surface..
202. Tomonori Iizuka, Yoshito Ohtake, Keiji Tanaka, A synergistic effect of light and heat on degradation for polypropylene, Zairyo/Journal of the Society of Materials Science, Japan, 10.2472/jsms.66.238, 66, 3, 238-243, 2017.03, Oxidative degradation of polypropylene (PP) is accelerated by not only sunlight but also temperature. Here we propose how the degradation behavior of PP under ultraviolet light irradiation conditions at elevated temperatures, which are more severe than the standards set by the Japanese Industrial Standards (JIS), can be examined. Fourier-transform infrared spectroscopy in conjunction with gel permeation chromatography revealed that the combination of light and heat definitely accelerated the chain scission, or oxidative degradation, of PP, resulting in deterioration of mechanical properties for PP..
203. Biao Zuo, Yue Liu, Yongfeng Liang, Daisuke Kawaguchi, Keiji Tanaka, Xinping Wang, Glass Transition Behavior in Thin Polymer Films Covered with a Surface Crystalline Layer, Macromolecules, 10.1021/acs.macromol.6b02740, 50, 5, 2061-2068, 2017.03, Thin amorphous poly(ethylene terephthalate) (PET) films covered with/without a crystallized surface layer were prepared onto silicon wafers. In the former and latter cases, the surface mobility in the film was depressed and enhanced, respectively. The glass transition temperature (Tg) of the amorphous PET film decreased with the reduction of the film thickness, exhibiting a remarkable nanoconfinement effect. However, once the surface region of the thin film was crystallized, or frozen in terms of the segmental motion, Tg of the films recovered to that of the bulk. Concurrently, the apparent activation energy of the segmental motion in the surface-crystallized film was in good accordance with the bulk value as well. These results make it clear that the mobility in the surface region plays an essential role in the glass transition of the thin films..
204. Yuji Matsumoto, Atsuomi Shundo, Masashi Ohno, Nobutomo Tsuruzoe, Masahiro Goto, Keiji Tanaka, Evolution of heterogeneity accompanying sol-gel transitions in a supramolecular hydrogel, Soft Matter, 10.1039/c7sm01612c, 13, 40, 7433-7440, 2017.01, When a peptide amphiphile is dispersed in water, it self-assembles into a fibrous network, leading to a supramolecular hydrogel. When the gel is physically disrupted by shaking, it transforms into a sol state. After aging at room temperature for a while, it spontaneously returns to the gel state, called sol-gel transition. However, repeating the sol-gel transition often causes a change in the rheological properties of the gel. To gain a better understanding of the sol-gel transition and its reversibility, we herein examined the thermal motion of probe particles at different locations in a supramolecular hydrogel. The sol obtained by shaking the gel was heterogeneous in terms of the rheological properties and the extent decreased with increasing aging time. This time course of heterogeneity, or homogeneity, which corresponded to the sol-to-gel transition, was observed for the 1st cycle. However, this was not the case for the 2nd and 3rd cycles; the heterogeneity was preserved even after aging. Fourier-transform infrared spectroscopy, small-angle X-ray scattering, and atomic force and confocal laser scanning microscopies revealed that, although the molecular aggregation states of amphiphiles both in the gel and sol remained unchanged with the cycles, the fibril density diversified to high and low density regions even after aging. The tracking of particles with different sizes indicated that the partial mesh size in the high density region and the characteristic length scale of the density fluctuation were smaller than 50 nm and 6 μm, respectively..
205. Manabu Inutsuka, Masayuki Haraguchi, Masaaki Ozawa, Norifumi L. Yamada, Keiji Tanaka, Adhesion Control of Elastomer Sheet on the Basis of Interfacial Segregation of Hyperbranched Polymer, ACS Macro Letters, 10.1021/acsmacrolett.8b00971, 8, 3, 267-271, 2019.03, Adhesion of a model rubbery material, cross-linked poly(dimethylsiloxane) (PDMS), onto a solid surface was studied by sum-frequency generation spectroscopy and X-ray photoelectron spectroscopy. To do so, here, we have focused on the adhesive deposit and insoluble layer. The former and latter were defined as the residual amount on the substrate after the peeling and residual layer after washing with a good solvent, respectively. The peel strength of a PDMS sheet adhered onto a glass plate increased with the contact time. Both adhesive deposit and insoluble layer also exhibited comparable contact time dependence. Once a hyperbranched polymer (HBP), which was segregated to the adhesive interface, was incorporated into PDMS, the peel strength and adhesive deposit decreased, although the thickness of the insoluble layer remained almost unchanged. These results suggest that the formation of loosely adsorbed chains on the solid surface, which possess not only trains but also many loop portions and tail parts, plays an important role in the macroscopic adhesion behavior of the PDMS sheet and the interfacial segregation of HBP can prevent it..
206. Mika Aoki, Atsuomi Shundo, Riichi Kuwahara, Satoru Yamamoto, Keiji Tanaka, Mesoscopic Heterogeneity in the Curing Process of an Epoxy-Amine System, Macromolecules, 10.1021/acs.macromol.8b02416, 52, 5, 2075-2082, 2019.03, Epoxy resins are composed of a three-dimensional network formed by chemical reactions between epoxy and amino compounds, which plays an important role in the mechanical properties. Thus, to use epoxy resins in various applications, it is necessary to gain a better understanding of their network structure. Here, we study the structural heterogeneity evolved in an epoxy-amine mixture during the curing process on the basis of a particle tracking technique, in which the thermal motion of probe particles in the mixture was tracked, small-angle X-ray scattering measurements in conjunction with coarse-grained molecular dynamics simulation. The heterogeneous environment was generated even at the initial stage of the curing process. Notably, the characteristic length scale was on the order of several hundreds of nanometers down to several tens of nanometers, depending on the extent of curing. Once a reaction occurs between a pair of epoxy and amino groups, the temperature at the site is locally elevated due to the heat of formation, accelerating a subsequent reaction nearby. Repeating such a situation, actively and scarcely reacted domains are formed. This is the main origin of the structural heterogeneity in epoxy resins..
207. Kentaro Yamamoto, Daisuke Kawaguchi, Kazuki Sasahara, Manabu Inutsuka, Satoru Yamamoto, Kiminori Uchida, Kazuki Mita, Hiroki Ogawa, Mikihito Takenaka, Keiji Tanaka, Aggregation States of Poly(4-methylpentene-1) at a Solid Interface, Polymer Journal, 10.1038/s41428-018-0134-7, 51, 2, 247-255, 2019.02, A thin film of poly(4-methylpentene-1) (P4MP1) was prepared on a quartz substrate, which was a model system of an interface in filler-reinforced semicrystalline polymer composites. Grazing-incidence wide-angle X-ray diffraction measurements revealed that P4MP1 in the thin film after isothermal crystallization formed a Form I crystal polymorph composed of a tetragonal unit cell with a 72 helix, in which the chain axis was oriented along the direction parallel to the quartz interface. Combining sum-frequency generation vibrational spectroscopy with molecular dynamics simulation enabled us to gain access to the local conformation of P4MP1 chains at the quartz interface and the changes that occurred with isothermal crystallization. Finally, the way in which the initial chain orientation at the substrate interface impacted the crystalline structure in the thin film was discussed..
208. Yudai Ogata, Tatsuki Abe, Shigeki Yonemori, Norifumi L. Yamada, Daisuke Kawaguchi, Keiji Tanaka, Impact of the Solid Interface on Proton Conductivity in Nafion Thin Films, Langmuir, 10.1021/acs.langmuir.8b03396, 34, 50, 15483-15489, 2018.12, Proton conductivity of polyelectrolytes in the interfacial region with a solid is key to the performance of polyelectrolyte-based fuel cells. The proton conductivity of Nafion thin films was examined as a function of the thickness along both directions, normal and parallel to the interface. Neutron reflectivity measurements revealed that a water-containing multilamellar structure was formed at the substrate interface. The presence of the interfacial layer, or the two-dimensional proton-conductive pathway, suppressed and enhanced the out-of-plane and in-plane proton conductivities, respectively. The method of proton conductivity in the interfacial region differed from that in the bulk, namely, the Grotthuss mechanism. Using laminated films, we conclude by showing that the proton conductivity in the Nafion thin film changes on the basis of the interface-to-volume ratio. This knowledge will be helpful for the design of devices containing polyelectrolytes with solid materials..
209. Hung K. Nguyen, Manabu Inutsuka, Daisuke Kawaguchi, Keiji Tanaka, Direct Observation of Conformational Relaxation of Polymer Chains at Surfaces, ACS Macro Letters, 10.1021/acsmacrolett.8b00411, 7, 10, 1198-1202, 2018.10, Sum-frequency generation spectroscopy was employed to follow the conformation evolution of polystyrene chains at the surface of a spin-coated film in a temperature-ramping mode as well as under isothermal annealing. The conformation of surface chains in an as-cast film was observed to be in a nonequilibrium state, in accordance with reported results for polymer chains in thin spin-coated films. While the relaxation of surface nonequilibrium chains was induced by the enhanced surface mobility, the whole chain motion such as reptation might be a key factor in determining the time scale for equilibrating the surface chain conformation..
210. Hoyeon Kim, Daisuke Kawaguchi, Keiji Tanaka, Yongsok Seo, Fracture Mechanism Change at a Heterogeneous Polymer-Polymer Interface Reinforced with in Situ Graft Copolymers, Langmuir, 10.1021/acs.langmuir.8b01860, 34, 37, 11027-11033, 2018.09, Dynamic secondary-ion mass spectroscopy (DSIMS) was used to investigate the change in the failure mechanism at a heterogeneous polymer-polymer interface (polystyrene (PS)/polyamide (nylon 6, Ny6)) reinforced with in situ graft copolymers produced by the reaction between Ny6 molecules and poly(styrene-co-maleic anhydride) at the interface. The variation in fracture toughness with bonding time and temperature has been explained by two different failure mechanisms: adhesive failure at the interface for short bonding times and when the bonding temperature is low and cohesive failure between chains at the interface and bulk PS for longer bonding times and when the bonding temperature is high. DSIMS results provide the direct experimental evidence that the nonreactive molecules (PS) diffuse away from the high-potential interface, which induces the cohesive failure in the bulk of the nonreactive molecules (PS) after long annealing times. The change in the adhesion strength with temperature could also cause a change in the failure mechanism. Common features of the fracture mechanisms at heterogeneous interfaces reinforced by the in situ graft copolymers are outlined, which are independent of the polymer crystallinity..
211. Hidenobu Taneda, Atsuomi Shundo, Hisao Matsuno, Keiji Tanaka, Design of a Well-Defined Polyrotaxane Structure on a Glassy Polymer Surface, Langmuir, 10.1021/acs.langmuir.7b03130, 34, 2, 709-714, 2018.01, 水界面における高分子鎖のダイナミクスは、生体関連機能の発現において重要な役割を果たすと考えられている。したがって、分子鎖ダイナミクスの制御のための一つの戦略は、ポリマー鎖を環状化合物で包接し、複合体を形成することであるが、そのような検討はこれまでバルク試料に限られていた。本研究では、典型的なガラス状高分子であるポリメタクリル酸メチルの膜を調製し、クリック反応とLangmuir-Blodgett法を組み合わせることで、膜最表面にポリ(エチレンオキシド)(PEO)と-シクロデキストリン(CD)からなるポリロタキサン構造を導入することに成功している。また、水界面でのPEOの熱運動が、CD分子の導入によって抑制され、その結果、タンパク質吸着や血小板接着のような生物学的応答が変化することを始めて示している。.
212. Atsuomi Shundo, 堀 耕一郎, Yasuyuki Tezuka, Takuya Yamamoto, Keiji Tanaka, Load-Induced Frictional Transition at a Well-Defined Alkane Loop Surface, LANGMUIR, 10.1021/acs.langmuir.6b04042, 33, 9, 2396-2401, 2017.03, 自己組織化単分子膜(SAM)は、材料表面に望みの物性・機能性を与えるための分子ツールとして注目され、実デバイスなどにも広く用いられてきた。しかしながら、これまで、SAM形成は線状分子に限定されており、表面物性・機能性への分子末端の影響が避けられないなどの問題があった。しかしながら、本研究では、環状アルカンジスルフィドを用いることで炭化水素環状鎖からなるSAMを形成することに成功し、表面物性・機能性への分子末端の影響を明確にしている。この結果は、材料表面の物性・機能性設計へ新たな指針を提案するものとして高く評価されている。.
213. Toyoaki Hirata, Hisao Matsuno, Daisuke Kawaguchi, Manabu Inutsuka, Tomoyasu Hirai, Masaru Tanaka, Keiji Tanaka, Dynamics of a bioinert polymer in hydrated states by dielectric relaxation spectroscopy, Physical Chemistry Chemical Physics, 10.1039/c6cp07322k, 19, 2, 1389-1394, 2017, The chain dynamics of well-defined poly(2-methoxyethyl acrylate) (PMEA), which has been used in practice as a bioinert coating for heart-lung machines, was examined as a function of water content by dielectric relaxation spectroscopy (DRS). Two relaxation processes observed in both dried and hydrated films were assigned to the segmental motion (α-process) and the relatively smaller scale motion such as the hindered rotation of side chains (β-process). Water molecules adsorbed on PMEA made the α-process faster, meaning that water molecules in PMEA played the role of a plasticizer. Combining the above knowledge with the depth dependence of water content in the PMEA film previously obtained by neutron reflectivity, the segmental dynamics of PMEA at the water interface, which should be crucial to bio-inertness, is discussed. We found that the segmental motion was markedly faster than that in the bulk and almost comparable to the side chain motion..
214. Biao Zuo, Manabu Inutsuka, Daisuke Kawaguchi, Xinping Wang, Keiji Tanaka, Conformational Relaxation of Poly(styrene- co -butadiene) Chains at Substrate Interface in Spin-Coated and Solvent-Cast Films, Macromolecules, 10.1021/acs.macromol.7b02756, 51, 6, 2180-2186, 2018.03, The local conformation of poly(styrene-co-butadiene) rubber (SBR) chains in direct contact with a quartz substrate was examined by interface-sensitive sum-frequency generation (SFG) spectroscopy. SFG signals, which could be obtained from functional groups only oriented at the interface, were clearly observed for SBR in a film at room temperature which was much higher than the bulk glass transition temperature (Tg). When the film was thermally annealed, SBR chains at the quartz interface changed their conformation to one with a lower energy state, accompanied by the randomization of both the main and side chain parts. The characteristic temperature, at which interfacial chains started to lose their orientations, was much higher than the bulk Tg. Also, the extent found to be more remarkable for the spin-coated film than for the solvent-cast one. This implies that the stress accumulated at the interface, which resulted from the centrifugal force during the spin-coating process, accelerates the mobility of chains there. Finally, the kinetics experiment well supports the slower orientation relaxation at the interface..
215. Hung K. Nguyen, Asuka Konomi, Shin Sugimoto, Manabu Inutsuka, Daisuke Kawaguchi, Keiji Tanaka, Rotational Dynamics of a Probe in Rubbery Polymers Characterized by Time-Resolved Fluorescence Anisotropy Measurement, Macromolecular Chemistry and Physics, 10.1002/macp.201700329, 219, 3, 2018.02, The rotational relaxation time (τrot) of a fluorescent molecule, coumarin 153 (C153), dispersed in different rubbery polymers is characterized by time-resolved fluorescence anisotropy measurement, and an attempt is made to quantitatively combine it with the segmental relaxation time (τseg) of the corresponding matrix polymer obtained by dielectric relaxation spectroscopy. This study here demonstrates that τseg extrapolated to higher temperatures using the Vogel–Fulcher–Tammann law can be superimposed on τrot, resulting in a single curve. This behavior is common for polymers with different glass transition temperatures such as polyisoprene and acrylonitrile/butadiene copolymer, implying that the rotational dynamics of C153 is a useful tool for the characterization of polymer dynamics..
216. Hisao Matsuno, Shunya Irie, Toyoaki Hirata, Ruriko Matsuyama, Yukari Oda, Hiroyasu Masunaga, Yukiko Seki, Sadahito Aoshima, Keiji Tanaka, Heterogeneous adhesion of cells on polymer surfaces with underlying amorphous/crystalline phases, Journal of Materials Chemistry B, 10.1039/c7tb03250a, 6, 6, 903-907, 2018.01, Fibroblastic adhesion behaviour on films of a poly[(2-methoxyethyl vinyl ether) (PMOVE)-block-(l-lactic acid) (PLLA)], in which the surface was covered with PMOVE, was studied. Fibroblasts were sufficiently sensitive to identify crystalline/non-crystalline regions existing beneath the surface PMOVE layer..
217. Mani Sen, Naisheng Jiang, Maya K. Endoh, Tadanori Koga, Alexander Ribbe, Atikur Rahman, Daisuke Kawaguchi, Keiji Tanaka, Detlef M. Smilgies, Locally Favored Two-Dimensional Structures of Block Copolymer Melts on Nonneutral Surfaces, Macromolecules, 10.1021/acs.macromol.7b02506, 51, 2, 520-528, 2018.01, Self-assembly of block copolymers (BCPs) into arrays of well-defined nanoscopic structures has attracted extensive academic and industrial interests over the past several decades. In contrast to the bulk where phase behavior is controlled by the segmental interaction parameter, the total number of segments in BCPs and volume fraction, the morphologies and orientations of BCP thin films can also be strongly influenced by the substrate surface energy/chemistry effect (considered as a "substrate field"). Here, we report the formation of locally favored structures where all constituent blocks coexist side-by-side on nonneutral solid surfaces irrespective of their chain architectures, microdomain structures, and interfacial energetics. The experimental results using a suite of surface-sensitive techniques intriguingly demonstrate that individual preferred blocks and nonpreferred blocks lie flat on the substrate surface and form a two-dimensional percolating network structure as a whole. The large numbers of solid-segment contacts, which overcome a loss in the conformational entropy of the polymer chains, prevent the structure relaxing to its equilibrium state (i.e., forming microdomain structures) even in a (good) solvent atmosphere. Our results provide direct experimental evidence of the long-lived, nonequilibrium structures of BCPs and may point to a new perspective on the self-assembly of BCP melts in contact with impenetrable solids..
218. Shin Sugimoto, Manabu Inutsuka, Daisuke Kawaguchi, Keiji Tanaka, Reorientation Kinetics of Local Conformation of Polyisoprene at Substrate Interface, ACS Macro Letters, 10.1021/acsmacrolett.7b00927, 7, 1, 85-89, 2018.01, The performance of a polymer composite material, in which inorganic fillers are dispersed, is closely related to the aggregation states and dynamics of polymer chains at the interface with the filler. In this study, the local conformation of polyisoprene (PI) at a quartz substrate interface was studied as a model system for the rubber/filler composite material. PI films were prepared from a toluene solution onto quartz substrates by a spin-coating method. Sum-frequency generation spectroscopy revealed that the local conformation of PI chains at the quartz interface depended on the spinning rate. The tilt angle of methyl groups increased with the rotational speed, probably due to the centrifugal force applied to chains and probably also the evaporation rate of the solvent during the solidification process. This result indicates that the interfacial orientation of PI chains can remain even at room temperature, which is 87 K higher than the bulk glass transition temperature (Tg b). The interfacial orientation disappeared at a temperature approximately 120 K higher than Tg b..
219. Nozomi Itagaki, Yukari Oda, Toyoaki Hirata, Hung Kim Nguyen, Daisuke Kawaguchi, Hisao Matsuno, Keiji Tanaka, Surface Characterization and Platelet Adhesion on Thin Hydrogel Films of Poly(vinyl ether), Langmuir, 10.1021/acs.langmuir.7b03427, 33, 50, 14332-14339, 2017.12, Poly(vinyl ether), with short oxyethylene side chains which possess a simple and relatively polar structure, should be a unique candidate for a bioinert material thanks to its solubility in water. On the basis of living cationic copolymerization and subsequent ultraviolet light irradiation, thin films of poly(2-methoxyethyl vinyl ether) with different cross-linking densities were prepared on solid substrates. The films were thickened in water, and the extent was dependent on the cross-linking density. Although the surface chemistry and aggregation states were almost identical to one another, the stiffness, or the softness, of the outermost region in the film was strongly dependent on the cross-linking density. That is, the interface between polymer and water became thicker, or more diffused, with decreasing cross-linking density. The blood compatibility based on the platelet adhesion on to the hydrogel films was better for a more diffused interface..
220. Deborah A. Barkley, Naisheng Jiang, Mani Sen, Maya K. Endoh, Jonathan G. Rudick, Tadanori Koga, Yugang Zhang, Oleg Gang, Guangcui Yuan, Sushil K. Satija, Daisuke Kawaguchi, Keiji Tanaka, Alamgir Karim, Chain Conformation near the Buried Interface in Nanoparticle-Stabilized Polymer Thin Films, Macromolecules, 10.1021/acs.macromol.7b01187, 50, 19, 7657-7665, 2017.10, It is known that when nanoparticles are added to polymer thin films, they often migrate to the film-substrate interface and form an "immobile interfacial layer", which is believed to be the mechanism behind dewetting suppression. We here report a new mechanism of dewetting suppression from the structural aspect of polymer chains accommodated at the film-substrate interface. Dodecanethiol-functionalized gold (Au) nanoparticles embedded in relatively low molecular weight PS thin films prepared on silicon (Si) substrates were used as a model. We mimicked the previously reported conditions, where the nanoparticles preferentially migrate to the substrate, and successfully stabilized the PS thin films via thermal annealing. A suite of surface-sensitive techniques including atomic force microscopy, grazing incidence small-angle X-ray scattering, X-ray/neutron reflectivity, and sum frequency generation spectroscopy in conjunction with the established solvent leaching process enabled us to unveil the polymer chain conformation and the dispersion structure of the nanoparticles at the film-substrate interface. The results evidenced that thermal annealing promotes irreversible polymer adsorption onto the substrate surface along with the migration of the nanoparticles. In addition, we found that the migration of the nanoparticles causes the changes in the conformations and interfacial orientations of the adsorbed polymer chains compared to those of the adsorbed polymer chains formed in the nanoparticle-free PS thin film. The resultant interfacial polymer structure allows for the interpenetration between free chains and the adsorbed chains, thereby stabilizing the thin film..
221. Kentaro Yamamoto, Tomoyasu Hirai, Yukari Oda, Daisuke Kawaguchi, Hisao Matsuno, Keiji Tanaka, A Polymer Interfacial Modifier Synthesized by Living Anionic Polymerization
Incorporation of Inorganic Blocks to Chain Ends, Macromolecular Chemistry and Physics, 10.1002/macp.201600473, 218, 12, 2017.06, As a polymer interfacial modifier, poly(methyl methacrylate) (PMMA) terminated with elemental blocks of polyhedral oligomeric silsesquioxane (POSS) has been exploited through the phenomenon of preferential segregation in PMMA films. The modifier synthesized by living anionic polymerization using a bifunctional initiator is segregated at the surface in the mixture of PMMA due to a “buoy” effect of the POSS blocks. This further results in the surface wettability of PMMA being regulated on the basis of the amount of the modifier fed into the matrix. Finally, it is shown that the amount of the modifier in the PMMA films affects the cell proliferation behavior via the wettability. (Figure presented.)..
222. Hung Kim Nguyen, Manabu Inutsuka, Daisuke Kawaguchi, Keiji Tanaka, Depth-resolved local conformation and thermal relaxation of polystyrene near substrate interface, Journal of Chemical Physics, 10.1063/1.4976523, 146, 20, 2017.05, By means of sum-frequency generation spectroscopy, we report a depth-resolved measurement of the local conformation and chain relaxation of polystyrene (hPS) located at different distances from the quartz interface. To control the distance from the quartz interface, deuterated polystyrene (dPS) layers with thicknesses of 3.4, 7.5, and 20 nm were coated on the quartz substrates. The hPS chains in direct contact with the substrate surface predominantly orient their phenyl rings in a direction normal to the substrate. This conformation was found to be barely relaxed when the film was annealed for 24 h at 423 K, higher than the bulk glass transition temperature. In contrast, for the hPS chains supported on the dPS layer, the orientation of phenyl rings of hPS became weaker with the annealing and this trend was more significant with increasing distance from the quartz substrate. In particular, the orientation of phenyl rings of hPS after annealing vanished at a distance of 20 nm. These results might provide an important evidence of the difference in the relaxation dynamics of the PS chains located at different distances from the quartz interface..
223. Biao Zuo, Yue Liu, Yongfeng Liang, Daisuke Kawaguchi, Keiji Tanaka, Xinping Wang, Glass Transition Behavior in Thin Polymer Films Covered with a Surface Crystalline Layer, MACROMOLECULES, 10.1021/acs.macromo1.6b02740, 50, 5, 2061-2068, 2017.03.
224. Shinichiro Shimomura, Hisao Matsuno, Kazuaki Sanada, Keiji Tanaka, Cell Adhesion on Glassy Scaffolds with a Different Mechanical Response, JOURNAL OF MATERIALS CHEMISTRY B, 10.1039/c6tb02617f, 5, 4, 714-719, 2017.03.
225. Shin Sugimoto, Yukari Oda, 平田 豊章, Ruriko Matsuyama, Hisao Matsuno, Keiji Tanaka, Surface segregation of a branched polymer with hydrophilic poly[2-(2-ethoxy)ethoxyethyl vinyl ether] side chains, POLYMER CHEMISTRY, 10.1039/c6py01984f, 8, 3, 505-510, 2017.01.
226. 平田 豊章, Hisao Matsuno, Daisuke Kawaguchi, Manabu Inutsuka, Tomoyasu Hirai, Masaru Tanaka, Keiji Tanaka, Dynamics of a bioinert polymer in hydrated states by dielectric relaxation spectroscopy, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10.1039/c6cp07322k, 19, 2, 1389-1394, 2017.01.
227. Shinichiro Shimomura, Manabu Inutsuka, Norifumi L. Yamada, Keiji Tanaka, Unswollen layer of cross-linked polyisoprene at the solid interface, POLYMER, 10.1016/j.polymer.2016.07.047, 105, 526-531, 2016.11.
228. Yuma Morimitsu, Hisao Matsuno, Noboru Ohta, Hiroshi Sekiguchi, Keiji Tanaka, Direct Correlation between Molecular Cross-linking and Macroscopic Mechanical Properties for Green Solids of Deoxyribonucleic Acids, CHEMNANOMAT, 10.1002/cnma.201600222, 2, 11, 1023-1027, 2016.11.
229. Chien-Chung Shih, Cheng-Yu Chung, Hung-Chin Wu,, Yuma Morimitsu, Hisao Matsuno, Keiji Tanaka, Wen-Chang Chen, Transparent Deoxyribonucleic Acid Substrate with High Mechanical Strength for Flexible and Biocompatible Organic Resistive Memory Devices, ChemComm, 10.1039/c6cc07648c, 52, 92, 13463-13466, 2016.11.
230. Atsuomi Shundo, 堀 耕一郎, PENALOZA DAVID JR PENULIAR, Yuji Matsumoto, Yasushi Okumura, Hirotsugu Kikuchi , Kyung Eun Lee, Sang Ouk Kim, Keiji Tanaka, Hierarchical Spatial Heterogeneity in Liquid Crystals Composed of Graphene Oxides, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10.1039/c6cp03614g, 18, 32, 22399-22406, 2016.08.
231. Shinichiro Shimomura, Manabu Inutsuka, Koichiro Tajima, Masaaki Nabika, Satoru Moritomi, Hisao Matsuno, Keiji Tanaka, Stabilization of Polystyrene Thin Films by Introduction of a Functional End Group, POLYMER JOURNAL, 10.1038/pj.2016.58, 48, 9, 949-953, 2016.09.
232. Hisao Matsuno, Ryota Tsukamoto, Yu Kaneshiro, Satoru Yamada, Keiji Tanaka, Platelet Adhesion on Films of Poly(vinylene carbonate) and Its Derivatives, CHEMISTRY LETTERS, 10.1246/cl.160373, 45, 8, 913-915, 2016.08.
233. Yukari Oda, Cui Zhang, Daisuke Kawaguchi, Hisao Matsuno, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Design of Blood-Compatible Interfaces with Poly(vinyl ether)s, ADVANCED MATERIALS INTERFACES, 10.1002/admi.201600034, 3, 12, 2016.06.
234. Hisao Matsuno, Ryota Tsukamoto, Shinichiro Shimomura, Tomoyasu Hirai, Yukari Oda, Keiji Tanaka, Platelet-adhesion Behavior Synchronized with Surface Rearrangement in a Film of Poly(methyl methacrylate) Terminated with Elemental Blocks, POLYMER JOURNAL, 10.1038/pj.2015.118, 48, 4, 413-419, 2016.04.
235. Shinichiro Shimomura, Hisao Matsuno, Toshiyuki Ohta, Seiichi Kawahara, Keiji Tanaka, Initial Adhesion of Fibroblasts on Thin Rubber Scaffolds, CHEMISTRY LETTERS, 10.1246/cl.160061, 45, 4, 475-477, 2016.04.
236. Mani Sen, Naisheng Jiang, Justin Cheung, Maya K. Endoh, Tadanori Koga, Daisuke Kawaguchi, Keiji Tanaka, Flattening Process of Polymer Chains Irreversibly Adsorbed on a Solid, ACS MACRO LETTERS, 10.1021/acsmacrolett.6b00169, 5, 4, 504-508, 2016.04.
237. Watanabe Motonori, Hidehisa Hagiwara, Yudai Ogata, Aleksandar Tsekov Staykov, Sean R. Bishop, Nicola H. Perry, Yuan Jay Chang, 伊田 進太郎, Keiji Tanaka, Tatsumi Ishihara, Impact of alkoxy chain length on carbazole-based, visible light-driven, dye sensitized photocatalytic hydrogen production, JOURNAL OF MATERIALS CHEMISTRY A, 10.1039/c5ta04991a, 3, 43, 21713-21721, 2015.11.
238. F. Chen, D. Peng, Yudai Ogata, Keiji Tanaka, Z. Yang, Yoshihisa Fujii, Norifumi L. Yamada, C. -H. Lam, O. K. C. Tsui, Confinement Effect on the Effective Viscosity of Plasticized Polymer Films, MACROMOLECULES, 10.1021/acs.macromol.5b01780, 48, 20, 7719-7726, 2015.10.
239. Takehiro Sagawa, Fuyuki Ito, Atsushi Sakai, Yudai Ogata, Keiji Tanaka, Hiroshi Ikeda, Substituent-dependent Backward Reaction in Mechanofluorochromism of Dibenzoylmethanatoboron Difluoride Derivatives, PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES, 10.1039/c5pp00453e, 15, 3, 420-430, 2016.03.
240. Yudai Ogata, Daisuke Kawaguchi, Keiji Tanaka, The Impact of Polymer Dynamics on Photoinduced Carrier Formation in Films of Semiconducting Polymers, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 10.1021/acs.jpclett.5b02255, 6, 23, 4794-4798, 2015.12.
241. Toyoaki Hirata, Hisao Matsuno, Daisuke Kawaguchi, Norifumi L. Yamada, Masaru Tanaka, Keiji Tanaka, Construction of a Blood-compatible Interface Based on Surface Segregation in a Polymer Blend, POLYMER, 10.1016/j.polymer.2015.10.001, 78, 219-224, 2015.11.
242. Manabu Inutsuka, Ayanobu Horinouchi, Keiji Tanaka, Aggregation States of Polymers at Hydrophobic and Hydrophilic Solid Interfaces, ACS MACRO LETTERS, 10.1021/acsmacrolett.5b00592, 4, 10, 1174-1178, 2015.10.
243. Keigo Matsumoto, Atsuomi Shundo, Masashi Ohno, Kowichiro Saruhashi, Nobuhide Miyachi, Nobutomo Tsuruzoe, Keiji Tanaka, Sol-gel Transition Accelerated by The Co-assembly of Two Components in Supramolecular Hydrogels, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10.1039/c5cp04800a, 17, 40, 26724-26730, 2015.10.
244. Hoyeon Lee, Seongjun Jo, Toyoaki Hirata, Norifumi L. Yamada, Keiji Tanaka, Eunkyoung Kim, Du Yeol Ryu, Interpenetration of Chemically Identical Polymer onto Grafted Substrates, POLYMER, 10.1016/j.polymer.2015.07.054, 74, 70-75, 2015.09.
245. Hisao Matsuno, Ruriko Matsuyama, Arisa Yamamoto, Keiji Tanaka, Enhanced Cellular Affinity for Poly(lactic acid) Surfaces Modified with Titanium Oxide, POLYMER JOURNAL, 10.1038/pj.2015.30, 47, 7, 505-512, 2015.07.
246. Toyoaki Hirata, Hisao Matsuno, Daisuke Kawaguchi, Norifumi L. Yamada, Masaru Tanaka, Keiji Tanaka, Effect of Interfacial Structure on Bioinert Properties of Poly(2-methoxyethyl acrylate)/poly(methyl methacrylate) Blend Films in Water, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10.1039/c5cp01972a, 17, 26, 17399-17405, 2015.07.
247. Mika Aoki, Daisuke Kawaguchi, Tatsuya Ganbe, Nobuyuki Sekine, Kenji Okamoto, Keiji Tanaka, Glass-transition Temperature Determination for Polymers Using Europium Complex as a Fluorescence Probe, CHEMISTRY LETTERS, 10.1246/cl.150013, 44, 5, 659-661, 2015.05.
248. Toshinori Moriga, Naoki Aoyama, Keiji Tanaka, Development of a Polyurethane Sealing Gasket with Excellent Sealing and Opening Properties, POLYMER JOURNAL, 10.1038/pj.2015.6, 47, 5, 400-407, 2015.05.
249. Yukari Oda, Daisuke Kawaguchi, Toyoaki Hirata, Norifumi L. Yamada, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Density Profiles of Well-defined Poly(methyl 2-propenyl ether) (PMPE) Near Water Interface, Macromolecular Symposia, 350, 1, 99-104, 2015.04.
250. Yudai Ogata, Daisuke Kawaguchi, Keiji Tanaka, An Effect of Molecular Motion on Carrier Formation in a Poly(3-hexylthiophene) Film, Scientific Reports, 10.1038/srep08436, 5, 8436, 2015.04, 本論文は、ポリ(3-ヘキシルチオフェン)(P3HT)膜の光電荷生成と分子運動について検討したものである。
P3HT 膜に光照射すると、正電荷と負電荷との対が形成された後、自発的に正および負電荷に分離されることを見出した。また、この電荷生成の速度定数は、低温では一定であるが、主鎖のねじれ運動に対応する緩和温度から
温度とともに増加した。
このことから、P3HT膜において分子運動は光電荷生成を支配する因子のひとつであると結論した。.
251. Toyoaki Hirata, Hisao Matsuno, Daisuke Kawaguchi, Tomoyasu Hirai, Norifumi L. Yamada, Masaru Tanaka, Keiji Tanaka, Effect of Local Chain Dynamics on a Bioinert Interface, LANGMUIR, 10.1021/acs.langmuir.5b00258, 31, 12, 3661-3667, 2015.03.
252. Tomoyasu Hirai, Shota Osumi, Hiroki Ogawa, Teruaki Hayakawa, Atsushi Takahara, Keiji Tanaka, Precise Synthesis and Surface Wettability of a Polymer with Liquid Crystalline Side Chains, MACROMOLECULES, 10.1021/ma5010265, 47, 15, 4901-4907, 2014.08.
253. Cui Zhang, Yukari Oda, Daisuke Kawaguchi, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Dynamic-driven Surface Segregation of a Hydrophilic Component in Diblock Copolymer Films, CHEMISTRY LETTERS, 10.1246/cl.140924, 44, 2, 166-168, 2015.02.
254. SIM JAE HYUN, Shuping Dong, Katrin Röemhild, Abdulaziz Kaya, Daewon Sohn, Keiji Tanaka, Maren Roman, Thomas Heinze, Alan R. Esker, 2-Hydroxypropyltrimethylammonium xylan adsorption onto rod-like cellulose nanocrystal, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 10.1016/j.jcis.2014.10.071, 440, 119-125, 2015.02.
255. Keigo Matsumoto, Atsuomi Shundo, Masashi Ohno, Shun Fujita, Kowichiro Saruhashi, Nobuhide Miyachi, Katsuaki Miyaji, Keiji Tanaka, Modulation of Physical Properties of Supramolecular Hydrogels based on a Hydrophobic Core, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10.1039/c4cp04395b, 17, 3, 2192-2198, 2015.01.
256. Daisuke Kawaguchi, Yohei Tateishi, Keiji Tanaka, Time-Resolved Fluorescence Analysis for Dye-Labeled Polystyrene in Thin Films, Journal of Non-Crystalline Solids, 10.1016/j.jnoncrysol.2014.09.010, 407, 284-287, 2015.01.
257. Hisao Matsuno, Toshiyuki Ohta, Atsuomi Shundo, Yasuo Fukunaga, Keiji Tanaka, Simple Surface Treatment of Cell-Culture Scaffolds with Ultrafine Bubble Water, LANGMUIR, 10.1021/la5035883, 30, 50, 15238-15243, 2014.12.
258. Motonori Watanabe, Hidehisa Hagiwara, Aoi Iribe, Yudai Ogata, Kenta Shiomi, Aleksandar Staykov, Shintaro Ida, Keiji Tanaka, Tatsumi Ishihara, Spacer Effects in Metal-free Organic Dyes for Visible-light-driven Dye-sensitized Photocatalytic Hydrogen Production, JOURNAL OF MATERIALS CHEMISTRY A, 10.1039/c4ta02720e, 2, 32, 12952-12961, 2014.08.
259. Atsuomi Shundo, Yuuki Hoshino, Takahiro Higuchi, Yuji Matsumoto, PENALOZA DAVID JR PENULIAR, Keigo Matsumoto, Masahi Ohno, Katsuaki Miyaji, Masahiro Goto, Keiji Tanaka, Facile Microcapsule Fabrication by Spray Deposition of a Supramolecular Hydrogel
, RSC Advances , 4, 68, 36097-36100, 2014.08.
260. Ayanobu Horinouchi, Norifumi L. Yamada, Keiji Tanaka, Aggregation States of Polystyrene at Nonsolvent Interfaces, LANGMUIR, 10.1021/la500829p, 30, 22, 6565-6570, 2014.06.
261. PENALOZA DAVID JR PENULIAR, Atsuomi Shundo, Keigo Matsumoto, Masashi Ohno, Katsuaki Miyaji, Masahiro Goto, Keiji Tanaka, Spatial Heterogeneity in the Sol-gel Transition of a Supramolecular System
, Soft Matter, 9, 21, 5166-5172, 2013.06.
262. Ayanobu Horinouchi, Keiji Tanaka, An Effect of Stereoregularity on the Structure of Poly(methyl methacrylate) at Air and Water Interfaces, RSC Advances, 3, 24, 9446-9452, 2013.06.
263. Atsuomi Shundo, Koichiro Hori, PENALOZA DAVID JR PENULIAR, Kazuki Yoshihiro, Annaka Masahiko, Keiji Tanaka, Nonsolvents-induced Swelling of Poly(methyl methacrylate) Nanoparticles
, Physical Chemistry Chemical Physics, 15, 39, 16574-16578, 2013.10.
264. Yudai Ogata, Daisuke Kawaguchi, Norifumi L. Yamada, Keiji Tanaka, Multistep Thickening of Nafion Thin Films in Water, ACS Macro Letters, 10.1021/mz400322q, 2, 10, 856-859, 2013.10.
265. Atsuomi Shundo, Koichiro Hori, Takuya Ikeda, Nobuo Kimizuka, Keiji Tanaka, Design of a Dynamic Polymer Interface for Chiral Discrimination, Journal of the American Chemical Society, 10.1021/ja404701s, 135, 28, 10282-10285, 2013.07.
266. Shinichiro Shimomura, Hisao Matsuno, Keiji Tanaka, Effect of Mechanical Instability of Polymer Scaffolds on Cell Adhesion, Langmuir, 10.1021/la4027706, 29, 35, 11087-11092, 2013.09.
267. Yukari Oda, Ayanobu Horinouchi, Daisuke Kawaguchi, Hisao Matsuno, Shokyoku Kanaoka, Sadahito Aoshima, Keiji Tanaka, Effect of Side-Chain Carbonyl Groups on the Interface of Vinyl Polymers with Water, Langmuir, 10.1021/la404802j, 30, 5, 1215-1219, 2014.02.
268. Jie Zhan, Hisao Matsuno, Hiroyasu Masunaga, Ogawa Hiroki, Keiji Tanaka, Green Solid Films with Tunable Mechanical Properties Made from Deoxyribonucleic Acid, NPG ASIA MATERIALS, 10.1038/am.2014.4, 6, e92, 2014.03.
269. Tomoyasu Hirai, Masayuki Haraguchi, Atsushi Sakai, PENALOZA DAVID JR PENULIAR, Masaaki Ozawa, Katsuaki Miyaji, Keiji Tanaka, Water-sliding Property of Polyacrylates with Different Fluoro Side Chains, CHEMISTRY LETTERS, 10.1246/cl.130012, 42, 5, 483-485, 2013.05.
270. Hironori Atarashi, Keiji Tanaka, Tomoyasu Hirai, Koichiro Hori, Masahiro Hino, Hiroshi Morita, Takeshi Serizawa, Uptake of Water in As-spun Poly(methyl methacrylate) Thin Films, RSC Advances, 10.1039/c3ra23066j, 3, 11, 3516-3519, 2013.03.
271. Keiji Tanaka, “One-pot Surface Modification of Rubbery Polymer Films”, Polym. Chem., 10.1039/C1PY00488C, 3, 2, 319-321 , 2011.12.
272. Atsuomi Shundo, Koichiro Hori, PENALOZA DAVID JR PENULIAR, Keiji Tanaka, "Optical Tweezers with Fluorescence Detection for Temperature-dependent Microrheological Measurements", REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.4789429, 84, 1, 014103-1-014103-5, 2013.01.
273. Masayuki Haraguchi, Tomoyasu Hirai, Masaaki Ozawa, Katsuaki Miyaji, Keiji Tanaka, "Hydrophobic Acrylic Hard Coating by Surface Segregation of Hyper-branched Polymers", APPLIED SURFACE SCIENCE, 10.1016/j.apsusc.2012.11.160, 266, 1, 235-238, 2013.02.
274. Hirofumi Tsuruta, Yukari Ikinaga, Yoshihisa Fujii, Keiji Tanaka, "A Simple Approach for Surface Hardening of Polystyrene", Applied Surface Science, 10.1016/j.apsusc.2012.10.070, 264, 1, 589-592, 2013.01.
275. Atsuomi Shundo, PENALOZA DAVID JR PENULIAR, Keiji Tanaka, "Microscopic Heterogeneity in Viscoelastic Properties of Molecular Assembled Systems", CHINESE JOURNAL OF POLYMER SCIENCE, 10.1007/s10118-013-1193-z, 31, 1, 1-11, 2013.01.
276. Cui Zhang, Yoshihisa Fujii, Keiji Tanaka, "Effect of Long Range Interactions on the Glass Transition Temperature of Thin Polystyrene Films", ACS MACRO LETTERS, 10.1021/mz300391g, 1, 11, 1317-1320, 2012.11.
277. Akihiro Matsubayashi, Kenji Fukunaga, Keiji Tanaka, "Metal Ions/ion Clusters Transport in Glassy Polymer Films: Construction of Multi-layered Polymer and Metal Composite Films", Journal of Materials Chemistry, 10.1039/c2jm31923c, 22, 31, 15578-15585, 2012.08.
278. Hirofumi Tsuruta, Yoshihisa Fujii, Naoki Kai, Hiroshi Kataoka, Takashi Ishizone, Masao Doi, Hiroshi Morita, Keiji Tanaka, "Local Conformation and Relaxation of Polystyrene at Substrate Interface", MACROMOLECULES, 10.1021/ma3007202, 45, 11, 4643-4649, 2012.06.
279. Ayanobu Horinouchi, Hironori Atarashi, Yoshihisa Fujii, Keiji Tanaka, "Dynamics of Water-Induced Surface Reorganization in Poly(methyl methacrylate) Films", MACROMOLECULES, 10.1021/ma3002559, 45, 11, 4638-4642, 2012.06.
280. Koichiro Hori, David P. Penaloza, Atsuomi Shundo, Keiji Tanaka, "Time-dependent heterogeneity in viscoelastic properties of worm-like micelle solutions"
, Soft Matter, 10.1039/c2sm25549a, 8, 28, 7361-7364, 2012.05.
281. Tomoyasu Hirai, Kaoru Kawasaki, Keiji Tanaka, "Interfacial kinetics of a model epoxy-amine addition reaction", Phys. Chem. Chem. Phys., 14, 39, 13532-13534 , 2012.01, 本論文はエポキシ/アミンのモデル反応に基づき、固体界面近傍における反応動力学評価を行ったものである。活性化エネルギー、衝突頻度因子の算出から、反応の活性化エネルギーはバルク、界面で不変である一方、バルクの衝突頻度因子は界面近傍におけるそれと比較して6倍程度であった。このことから、固体界面の存在はエポキシ硬化反応の化学的な因子には影響を与えず、物理的因子に大きな影響を与えることを明らかにした。.
282. Atsuomi Shundo, Yohei Okada, Fuyuki Ito, and Keiji Tanaka, ”Fluorescence Behavior of Dyes in Thin Films of Various Polymers”, Macromolecules, 10.1021/ma201901x, 45, 1, 2011.12.
283. K. Hori, H. Matsuno, K. Tanaka, “Sorption Kinetics of Methanol in Thin Poly(methyl methacrylate) Films Studied by Optical Reflectivity”, Soft Matter, 7 , 21, 10319-10326, 2011.09.
284. A. Matsubayashi, K. Fukunaga, T. Tsuji, K. Ataka, H. Ohsaki, K. Tanaka,, “Band-selective Mirror Characteristics of Polymer/Metal Multilayer Films”,, Chem. Lett., 10.1246/cl.2011.1138, 40, 10, 1138-1139, 2011.10.
285. Atsuomi Shundo, Keiko Mizuguchi, Misao Miyamoto, Masahiro Goto, Keiji Tanaka, “Controllable Heterogeneity in a Supramolecular Hydrogel”, Chem. Commun., 10.1039/c1cc12733k, 47, 31, 8844-8846, 2011.06.
286. Satoshi Miwa, Takako Kikuchi, Yoshito Ohtake, Keiji Tanaka, “Surface Degradation of Poly(ethylene-co-propylene-co-5-ethylidene-2-norbornene) Terpolymer by Ozone in Water”, Polym. Degrad. Stab., 10.1016/j.polymdegradstab.2011.05.001, 96, 8, 1503-1507, 2011.05.
287. T. Hirata, H. Matsuno, M. Tanaka, K. Tanaka, "Surface Segregation of Poly(2-methoxyethyl acrylate) in a Mixture with Poly(methyl methacrylate)”, Phys. Chem. Chem. Phys, 10.1246/cl.2011.366, 40, 4, 366-367, 2011.04.
288. H. Matsuno, J.-i. Nakahara, K. Tanaka, “Dynamic Mechanical Properties of Solid Films of Deoxyribonucleic Acid”, Biomacromolecules, 12 , 1, 173-178, 2011.01.
289. N. Idota, K. Nagase, K. Tanaka, T. Okano, M. Annaka, “Stereoregulation of Thermoresponsive Polymer Brushes by Surface-initiated Living Radical Polymerization and the Effect of Tacticity on Surface Wettability”, Langmuir, 26, 13 , 17781-17784, 2010.11.
290. Y. Tateishi, N. Kai, H. Noguchi, K. Uosaki, T. Nagamura, K. Tanaka, “Local Conformation of Poly(methyl methacrylate) at Nitrogen and Water Interfaces”, Polym. Chem., 1, 3, 303-311, 2010.04.
291. I. Narayama, K. Akabori, H. Morita, T. Nagamura, K. Tanaka, Nanoscopic Adhesion Test for Polymers by A Light-lever System, J. Phys. Conf. Ser. , 184, 012032 , 2009.09.
292. K. Tanaka, Y. Tateishi, Y. Okada, T. Nagamura, M. Doi, H. Morita, Interfacial Mobility of Polymers on Inorganic Solids
, J. Phys. Chem. B. , 113, 14, 4571-4577, 2009.04.
293. Y. Fujii, T. Nagamura, K. Tanaka, Relaxation Behavior of Poly(methyl Methacrylate) at a Water Interface, J. Phys. Chem. B. , 114, 10, 3457-3460 , 2010.03.
294. H. Atarashi, H. Morita, D. Yamazaki, M. Hino, T. Nagamura, K. Tanaka, Swelling Structure of Thin Poly(methyl methacrylate) Films in Various Alkyl Length Alcohols, J. Phys. Chem. Lett. , 1, 5, 881-885 , 2010.02.
295. Y. Fujii, Z. Yang, J. Leach, H. Atarashi, K. Tanaka, O. K. C. Tsui, Affinity of Polystyrene Films to Hydrogen-Passivated Silicon and its Relevance to the Tg of the Films, Macromolecules , 42, 19, 7418-7422, 2009.09.
296. Y. Fujii, H. Atarashi, M. Hino, T. Nagamura, K. Tanaka, Interfacial Width in Polymer Bilayer Films Prepared by Double Spin-coating and Floating Methods, ACS Appl. Mater. Interfaces, 1, 9, 1856-1859, 2009.09.
297. K. Akabori, H. Atarashi, M. Ozawa, T. Kondo, T. Nagamura, K. Tanaka, Glass Transition Behaviour of Hyper-branched Polymers, Polymer, 50, 20, 4868-4875, 2009.09.
298. T. Date, K. Tanaka, T. Nagamura, T Serizawa, Directional Affinity of Short Peptides for Synthetic Polymers
, Chem. Mater. , 20(14), 4536-4538 , 2008.07.
299. Y. Fujii, H. Atarashi, K. Akabori, M. Hino, K. Tanaka, T. Nagamura, Structural Analysis for A Poly(methyl methacrylate) Ultrathin Film in Water by Neutron Reflectivity, J. Phys. Conf. Ser., 83, 012023, 2007.10.
300. Y. Fujii, Hironori A., N. Yamada, N. Torikai, K. Tanaka, T. Nagamura, Interfacial Structure of Deuterated Poly(methyl Methacrylate) with Carbon Dioxide below the Bulk Glass Transition Temperature, Trans. Mater. Res. Soc. Japan, 32(1), 293-296, 2007.04.
301. H. Atarashi, F. Ariura, K. Akabori, A. Tanaka, M. Ozawa, K. Tanaka, T. Nagamura, Interfacial Segregation of Hyper-branched Polystyrene in Mixtures of Linear Component, Trans. Mater. Res. Soc. Japan, 32(1), 231-234, 2007.04.
302. Y. Fujii, H. Atarashi, T. Nagamura, K. Tanaka, Entanglement Effect on Film Retention of Poly(methyl methacrylate) in Methanol, Chem. Lett. , 37(3), 326-327, 2008.03.
303. H. Sugihara, K. Oya, H. Murase, K. Akabori, K. Tanaka, T. Kajiyama, A. Takahara, Simultaneous Imaging for Surface and Internal Structure of Polymer Blend Thin Films, Appl. Surf. Sci. , 254(10), 3180-3183, 2008.03.
304. K. Tanaka, Y. Fujii, H. Atarashi, M. Hino, T. Nagamura,, Non-solvents Cause Swelling at the Interface with Poly(methyl Methacrylate) Films, Langmuir , 24(1), 296-301 , 2008.01.
305. Y. Fujii, H. Atarashi, N. Yamada, N. Torikai, T. Nagamura, K. Tanaka, Gas Sorption into Surface of Poly(methyl methacrylate) Films at Atmospheric Pressure, Polym. J., 39(12), 1290-1294, 2007.12.
306. K. Niihara, U. Matsuwaki, N. Torikai, H. Atarashi, K. Tanaka, H. Jinnai, A Novel Structural Analysis for A Cylinder-forming Block Copolymer Thin Film Using Neutron Reflectivity Aided By Transmission Electron Microtomography, Macromolecules, 40(19), 6940-6946, 2007.09.
307. Y. Fujii, K. Akabori, K. Tanaka, T. Nagamura, Chain Conformation Effect on Molecular Motion at Surface in Poly(methyl Methacrylate) Films, Polym. J., 39(9), 928-934 , 2007.09.
308. Y. Tateishi, K. Tanaka, T. Nagamura, Kinetics of Photo-induced E to Z Isomerization for Azobenzene in Films; Thickness, Molecular Weight and Temperature Effects, J. Phys. Chem. B., 111(27), 7761-7766, 2007.07.
309. K. Akabori, K. Tanaka, N. Satomi, T. Nagamura, A. Takahara, T. Kajiyama, Effects of Static and Dynamic Forces on Surface Viscoelastic Response of Polymer Films in Scanning Viscoelasticity Microscopy, Polym. J. , 39(7), 684-689, 2007.07.
310. D. Kawaguchi, K. Tanaka, N. Torikai, A. Takahara, T. Kajiyama, Surface and Interfacial Segregation in Blends of Polystyrene with Functional End Groups and Deuterated Polystyrene, Langmuir , 23(13), 7269-7275, 2007.06.
311. H. Atarashi, K. Akabori, A. Tanaka, M. Ozawa, K. Tanaka, T. Nagamura, Graft Polymerization Initiated by Photo-sensitizer Segregated at Surface of Polymer Film Upon Ultraviolet Irradiation, Chem. Lett. , 36(6), 808-809 , 2007.06.
312. T.Kajiyama, K.Tanaka, I.Ohki, S.-R.Ge, J.-S.Yoon, A.Takahara, Imaging of Dynamic Viscoelastic Properties of a Phase-Separated Polymer Surface by Forced Oscillation Atomic Force Microscopy, Macromolecules, 10.1021/ma00104a061, 27, 26, 7932-7934, 27 :7932-7934, 1994.01.
313. K.Tanaka, J.-S.Yoon, A.Takahara, T.Kajiyama, Ultrathinning-Induced Surface Phase Separation of Polystyrene/Poly(vinyl methyl ether) Blend Film, Macromolecules, 10.1021/ma00108a021, 28, 4, 934-938, 28 : 934-938, 1995.01.
314. T.Kajiyama, K.Tanaka, A.Takahara, Depth Dependence of the Surface Glass Transition Temperature of a Poly(styrene-block-methyl methacrylate) Diblock Copolymer Film on the Basis of Temperature-Dependent X-ray Photoelectron Spectroscopy, Macromolecules, 10.1021/ma00113a059, 28, 9, 3482-3484, 28 : 3482-3484, 1995.01.
315. K.Tanaka, A.Takahara, T.Kajiyama, Surface Molecular Motion in Thin Films of Poly(styrene-block-methyl methacrylate) Diblock Copolymer, Acta Polym., 10.1002/actp.1995.010460612, 46, 6, 476-482, 46 : 476-482, 1995.01.
316. T.Kajiyama, K.Tanaka, I.Ohki, S.-R.Ge, A.Takahara, Direct Observation of Surface Morphology and Surface Viscoelastic Properties of Polymeric Solids Based on Scanning Force Microscopy, Proc.Japan Acad. B, 10.2183/pjab.71.75, 71, 2, 75-80, 71 :75-80, 1995.01.
317. K.Tanaka, A.Taura, S.-R.Ge, A.Takahara, T.Kajiyama, Molecular Weight Dependence of Surface Dymamic Viscoelastic Properties for the Monodisperse Polystyrene Film, Macromolecules, 10.1021/ma951378y, 29, 8, 3040-3042, 29 :3040-3042, 1996.01.
318. K.Tanaka, A.Takahara, T.Kajiyama, Film Thickness Dependence of Surface Structure of Immiscible Polystyrene/Poly(methyl methacrylate) Blends, Macromolecules, 10.1021/ma951140+, 29, 9, 3232-3239, 29 :3232-3239, 1996.01.
319. T.Kajiyama, K.Tanaka, A.Takahara, Surface Molecular Motion of the Monodisperse Polystyrene Films, Macromolecules, 10.1021/ma960582y, 30, 2, 280-285, 30 :280-285, 1997.01.
320. K.Tanaka, A.Takahara, T.Kajiyama, Effect of Polydispersity on Surface Molecular Motion of Polystyrene Films, Macromolecules, 10.1021/ma970057e, 30, 21, 6626-6632, 30 :6626-6632, 1997.01.
321. W.-K.Lee, J.-S.Yoon, K.Tanaka, N.Satomi, X.Jiang, A.Takahara, C.-S.Ha, T.Kajiyama, Relationships between Lateral Force Microscopy, Polym. Bull., 39 :369-376, 1997.01.
322. W.-K.Lee, K.Tanaka, A.Takahara, T.Kajiyama, C.-S.Ha, Surface Structure of Blend Films of Styrene/Acrylonitrile Copolymer and Poly(methyl methacrylate) (PMMA) or Hydrolyzed PMMA, Bull. Korean Chem. Soc., 18, 9, 958-961, 18 :958-961, 1997.01.
323. T.Kajiyama, K.Tanaka, A.Takahara, Surface Molecular Motion of Amorphous Polymeric Solids, Bull. Chem. Soc. Jpn., 10.1246/bcsj.70.1491, 70, 7, 1491-1503, 70 :1491-1503, 1997.01.
324. T.Kajiyama, K.Tanaka, A.Takahara, Analysis of Surface Molecular Motion of Amorphous Polymeric Solids on the Basis of Scanning Force Microscopy and X-ray Photoelectron Spectrocopy, Peoc. Japan Acad. B, 73 :132-137, 1997.01.
325. K.Tanaka, A.Takahara, T.Kajiyama, Surface Molecular Aggregation Structure and Surface Molecular Motions of High-Molecular-Weight Polystyrene/Low-Molecular-Weight Poly(methyl methacrylate) Blend Films, Macromolecules, 10.1021/ma9709866, 31, 3, 863-869, 31 (3): 863-869, 1998.02.
326. X.Jiang, K.Tanaka, A.Takahara, T.Kajiyama, Effect of Chain End Group Hydrophobicity on Surface Aggregation Structure of Poly(stylene-block-4-vinylpyridine) Symmetric Diblock Copolymer Films, Polymer, 10.1016/S0032-3861(97)00567-3, 39, 12, 2615-2620, 39 :2615-2620, 1998.01.
327. T.Kajiyama, K.Tanaka, A.Takahara, Surface Segregation of the Higher Surface Free Energy Component in Symmetric Polymer Blend Films, Macromolecules, 10.1021/ma971247s, 31, 11, 3746-3749, 31 :3746-3749, 1998.01.
328. K.Tanaka, X.Jiang, K.Nakamura, A.Takahara, T.Kajiyama, T.Ishizone, A.Hirao, S.Nakahama, Effect of Chain End Chemistry on Surface Molecular Motion of Polystyrene Films, Macromolecules, 10.1021/ma9712561, 31, 15, 5148-5149, 31 :5148-5149, 1998.01.
329. T.Kajiyama, K.Tanaka, N.Satomi, A.Takahara, Surface Relaxation Process of Monodisperse Polystyrene Film Based on Lateral Force Microscopic Measurements, Macromolecules, 10.1021/ma971274i, 31, 15, 5150-5151, 31 :5150-5151, 1998.01.
330. T.Kajiyama, K.Tanaka, A.Takahara, Study of the Surface Glass Transition Behavior of Amorphous Polymer Film by Scanning-Force Microscopy and Surface Spectroscopy, Polymer, 10.1016/S0032-3861(98)00049-4, 39, 19, 4665-4673, 39:4665-4673, 1998.01.
331. K.Tanaka, P.A.Manning, V.K.Lau, H.Yu, Lipid Lateral Diffusion in Dilauroylphosphatidylcholine/Cholesterol Mixed Monolayers at the Air/Water Interface, Langmuir, 15 (2): 600-606, 1999.01.
332. X.Jinang, K.Tanaka, A.Takahara, S.Nakahama, T.Kajiyama, Chain End Group-Induced Surface Ordering in Poly(stylene-b-4-vinylpyridine) Symmetric Diblock Copolymer Films, Polymer J., 10.1295/polymj.31.1015, 31, 11, 1015-1020, 31:1015-1020, 1999.01.
333. K.Tanaka, P.A.Manning, H.Yu, Lipase Catalysis on Monolayers at the Air/Water Interface. 1.Kinetic Rate Constants on Quasi-Two-Dimension, Langmuir, 16:2665-2671, 2000.01.
334. K.Tanaka, S.P.Mecca, H.Yu, Lipase Catalysis on Monolayers at the Air/Water Interface. 2.Diffusion-Controlled Kinetics on Quasi-Two Dimension, Langmuir, 2672-2676, 2000.01.
335. N.Miki, K.Tanaka, A.Takahara, T.Kajiyama, Secondary Ion Mass Spectroscopic Analysis of Copper Migration at the Copper/Polyimide Interface, J.Vac.Sci.Technol.B, 10.1116/1.591191, 18, 1, 313-316, 18:313-316, 2000.01.
336. T.Kajiyama, K.Tanaka, N.Satomi, A.Takahara,, Surface Glass Transition Temperatures of Monodisperse Polystyrene Films by Scanning Force Microscopy, Sci.Tech.Adv.Mater., 1:31-35, 2000.01.
337. T.Kajiyama, K.Tanaka, N.Satomi, A.Takahara, Surface Rheology of Polymeric Solids, Chinese J.Polym.Sci., 18, 3, 239-248, 18:239-248, 2000.01.
338. K. Tanaka, A. Takahara, T. Kajiyama, Rheological analysis of surface relaxation process of monodisperse polystyrene films, Macromolecules, 10.1021/ma000406w, 33, 20, 7588-7593, 33 (20): 7588-7593, 2000.10.
339. T.Kajiyama, D.Kawaguchi, A.Sakai, N.Satomi, K.Tanaka, A.Takahara, Determination Factors on Surface Glass Transition Temperatures of Polymeric Solids, High Perform. Polym., 10.1088/0954-0083/12/4/314, 12, 4, 587-597, 12:587-597, 2000.01.
340. X.Jiang, C.Z.Yang, K.Tanaka, A.Takahara, T.Kajiyama, Effect of Chain End Group on Surface Glass Transition Temperature of Thin Polymer Film, Phys. Lett. A, 10.1016/S0375-9601(01)00150-5, 281, 5-6, 363-367, 281:363-367, 2001.01.
341. T.Kajiyama, R.Tominaga, K.Kojio, K.Tanaka, Structual Study of Crystal Transition from Hexagonal to Rectangular Phase of Lignoceric Acid Monolayers, Bull. Chem. Soc. Jpn., 10.1246/bcsj.74.765, 74, 4, 765-771, 74:765-771, 2001.01.
342. K.Kojio, K.Tanaka, A.Takahara, T.Kajiyama, Novel Method to Prepare Organosilane Monolayer on Solid Substrate, Bull. Chem. Soc. Jpn., 10.1246/bcsj.74.1397, 74, 8, 1397-1401, 74:1397-1401, 2001.01.
343. H.-Q.Xiang, K.Tanaka, A.Takahara, T.Kajiyama, Reversible Reduction and Reoxidation of Langmuir-Blodgett Films of Octacyanophthalocyanine Dilithium Complex, Chem. Lett., 10.1246/cl.2001.536, 6, 536-537, 536-537, 2001.01.
344. N.Satomi, K.Tanaka, A.Takahara, T.Kajiyama, Effect of Internal Bulk Phase on Surface Viscoelastic Properties by Scanning Probe Microscopy, Macromolecules, 10.1021/ma001831s, 34, 18, 6420-6423, 34:6420-6423, 2001.01.
345. D.Kawaguchi, K.Tanaka, A.Takahara, T.Kajiyama, Surface Mobile Layer of Polystyrene Film below Bulk Glass Transition Temperature, Macromolecules, 10.1021/ma010012k, 34, 18, 6164-6166, 34:6164-6166, 2001.01.
346. X.Jiang, K.Tanaka, A.Sakai, A.Takahara, T.Kajiyama, Surface Relaxation Behavior of Proton-and Perfluoroalkyl-Terminated Poly(2-vinyl pyridine) Films, Polymer, 10.1016/S0032-3861(01)00384-6, 42, 21, 8959-8964, 42:8959-8964, 2001.01.
347. N. Satomi, K. Tanaka, A. Takahara, T. Kajiyama, T. Ishizone, S. Nakahama, Surface molecular motion of monodisperse (alpha,omega-diamino-terminated and (alpha,omega)-dicarboxy-terminated polystyrenes, Macromolecules, 10.1021/ma010126w, 34, 25, 8761-8767, 34 (25): 8761-8767, 2001.12.
348. K.Tanaka, H.Yu, Lipase Activity on Lipid/Polymer Binary Monolayers: Lateral Diffusion-Controlled Enzyme Kinetics, Langmuir, 18:797-804, 2002.01.
349. F.Xie, H.F.Zhang, F.K.Lee, O.K.C.Tsui, Y.Yokoe, K.Tanaka, A.Takahara, T.Kajiyama, T.He, Effect of Low Surface Energy Chain Ends on the Glass Transition Temperature of Polymer Thin Films, Macromolecules, 10.1021/ma011689a, 35, 5, 1491-1492, 35:1491-1492, 2002.01.
350. H.-Q.Xiang, K.Tanaka, A.Takahara, T.Kajiyama, Spectroscopic and Electrochemical Characterizations of Dilithium Octacyanophthalocyanine Langmuir-Blodgett Films, Langmuir, 10.1021/la011401a, 18, 6, 2223-2228, 18:2223-2228, 2002.01.
351. K. Tanaka, T. Kajiyama, A. Takahara, S. Tasaki, A novel method to examine surface composition in mixtures of chemically identical two polymers with different molecular weights, Macromolecules, 10.1021/ma011960o, 35, 12, 4702-4706, 35 (12): 4702-4706, 2002.06.
352. A.Sakai, K.Tanaka, T.Kajiyama, A.Takahara, Thermal Molecular Motion at Atactic Polypropylene Surfaces, Polymer, 10.1016/S0032-3861(02)00340-3, 43, 19, 5109-5115, 43:5109-5115, 2002.01.
353. H.-Q.Xiang, K.Tanaka, T.Kajiyama,, Gas-Sensing Properties of Dilithium Octacyanophthalocyanine Langmuir-Blodgett Films, Langmuir, 10.1021/la026161t, 18, 23, 9102-9105, 18:9102-9105, 2002.01.
354. K.Tanaka, K.Kojio, R.Kimura, A.Takahara, T.Kajiyama, Surface Relaxation Process of Poly(methyl methacrylate) Brushes Prepared by Atom Transfer Radical Polymerization, Polymer J., 10.1295/polymj.35.44, 35, 1, 44-49, 35:44-49, 2003.01.
355. A.Takahara, D.Kawaguchi, K.Tanaka, M.Tozu, T.Hoshi, T.Kajiyama, Analysis of Surface Composition of Isotopic Polymer Blends Based on Time-of-Flight Secondary Ion Mass Spectroscopy, Appl. Surf. Sci., 10.1016/S0169-4332(02)00748-1, 203, 538-540, 203-204:538-540, 2003.01.
356. K.Tanaka, S.Dai, T.Kajiyama, K.Aoi, M.Okada, Aggregation States and Molecular Motion in Amphiphilic Poly(amido amine) Dendrimer Monolayers on Solid Substrates, Langmuir, 10.1021/la0261592, 19, 4, 1196-1202, 19 (4): 1196-1202, 2003.02.
357. D.Kawaguchi, K.Tanaka, T.Kajiyama, A.Takahara, S.Tasaki, Mobility Gradient in Surface Region of Monodisperse Polystyrene Films, Macromolecules, 10.1021/ma025667f, 36, 4, 1235-1240, 36 (4): 1235-1240, 2003.02.
358. T.Kajiyama, D.Kawaguchi, K.Tanaka, Polymer Chain Diffusion at a Temperature below Its Bulk Glass Transition Temperature, Chinese J. Polym. Sci., 21, 2, 141-146, 21:141-146, 2003.01.
359. K.Akabori, K.Tanaka, T.Kajiyama, A.Takahara, Anomalous Surface Relaxation Process in Polystyrene Ultrathin Films, Macromolecules, 10.1021/ma034001y, 36, 13, 4937-4943, 36 (13): 4937-4943, 2003.07.
360. K.Tanaka, D.Kawaguchi, Y.Yokoe, T.Kajiyama, A.Takahara, S.Tasaki, Surface Segregation of Chain Ends in alpha,omega-Fluoroalkyl-Terminated Polystyrenes Films, Polymer, 10.1016/S0032-3861(03)00391-4, 44, 15, 4171-4177, 44:4171-4177, 2003.01.
361. K. Tanaka, K. Hashimoto, T. Kajiyama, A. Takahara, Visualization of active surface molecular motion in polystyrene film by scanning viscoelasticity microscopy, Langmuir, 10.1021/la034542g, 19, 17, 6573-6575, 19 (17): 6573-6575, 2003.08.
362. D. Kawaguchi, K. Tanaka, T. Kajiyama, A. Takahara, S. Tasaki, Surface composition control via chain end segregation in blend films of polystyrene and poly(vinyl methyl ether), Macromolecules, 10.1021/ma034117u, 36, 18, 6824-6830, 36 (18): 6824-6830, 2003.09.
363. T.Kajiyama, K.Tanaka, A.Takahara, Analysis of Surface Mobility in Polystyrene Films with Monodisperse and Bimodal Molecular Weights by Lateral Force Microscopy, J. Polym. Sci. Part A: Polym. Chem., 10.1002/pola.10873, 42, 3, 639-647, 42:639-647, 2004.01.
364. H.Yokoyama, K.Tanaka, A.Takahara, T.Kajiyama, K.Sugiyama, A.Hirao, Surface Structure of Asymmetric Fluorinated Block Copolymers: Poly[styrene-block-4-(perfluorooctylpropyloxy)styrene], Macromolecules, 10.1021/ma035191f, 37, 3, 939-945, 37:939-945, 2004.01.
365. K.Tanaka, F.Ariura, T.Nagamura, T.Kajiyama, Further Study of Chain End Effect on Surface Mobility in Monodisperse Polystyrene Films, Polymer J., 10.1295/polymj.36.498, 36, 6, 498-501, 36:498-501, 2004.01.
366. M.Hikita, K.Tanaka, T.Nagamura, T.Kajiyama, Aggregation States and Surface Wettability in Films of Poly(styrene-block-2-perfluooctyl ethyl acrylate)Diblock Copolymers Synthesized by Atom Transfer Radical Polymerization, Langmuir, 10.1021/la049556g, 20, 13, 5304-5310, 20:5304-5310, 2004.01.
367. N.Hosaka, K.Tanaka, H.Otsuka, A.Takahara,, Influence of the Addition of Silsesquioxane on the Dewetting Behavior of Polystyrene Thin Film, Compos. Interface., 10.1163/1568554041738157, 11, 4, 297-306, 11:297-306, 2004.01.
368. T.Izumi, K.Tanaka, R.Narita, S.Horiuchi, A.Takahara, T.Kajiyama, Annealing Effect on Adhesion Properties of Poly(butylene Terephthalate), Compos. Interface., 10.1163/1568554041738166, 11, 4, 325-333, 11:325-333, 2004.01.
369. K.Tanaka, Y.Tateishi, T.Nagamura, Photoisomerization of Azobenzene Probes Tagged to Polystyrene in Thin Films, Macromolecules, 10.1021/ma048579z, 37, 22, 8188-8190, 37:8188-8190, 2004.01.
370. A.Sakai, K.Tanaka, Y.Fujii, T.Nagamura, T.Kajiyama, Structure and Thermal Molecular Motion at Surface of Semi-Crystalline Isotactic Polypropylene Films, Polymer, 10.1016/j.polymer.2004.11.021, 46, 2, 429-437, 46:429-437, 2005.01.
371. H.Yakabe, K.Tanaka, T.Nagamura, S.Sasaki, O.Sakata, A.Takahara, T.Kajiyama, Grazing Incidence X-ray Diffraction Study on Surface Crystal Structure of Polyethylene Thin Films, Polym. Bull., 10.1007/s00289-004-0329-2, 53, 3, 213-222, 53:213-222, 2005.01.
372. H.Yokoyama, T.Miyamae, S.Han, T.Ishizone, K.Tanaka, A.Takahara, N.Torikai, Spontaneously Formed Hydrophilic Surfaces by Segregation of Block Copolymers with Water-Soluble Blocks, Macromolecules, 10.1021/ma050473w, 38, 12, 5180-5189, 38:5180-5189, 2005.01.
373. M.Hikita, K.Tanaka, T.Nakamura, T.Kajiyama, A.Takahara, Super Liquid Repellent Surfaces Prepared by Colloidal Silica Nano-Particles Covered with Fluoroalkyl Groups, Laugmuir, 10.1021/la050901r, 21, 16, 7299-7302, 21:7299-7302, 2005.01.
374. K.Akabori, K.Tanaka, T.Nagamura, A.Takahara, T.Kajiyama, Molecular Motion in Ultrathin Polystyrene Films: Dynamic Mechanical Analysis of Surface and Interfacial Effects, Macromolecules, 10.1021/ma051143e, 38, 23, 9735-9741, 38:9735-9741, 2005.01.
375. D.Kawaguchi, K.Masuoka, A.Takano, K.Tanaka, T.Nagamura, N.Torikai, R.M.Dalgliesh, S.Langridge, Y.Matsushita, Comparison of Interdiffusion Behavior between Cyclic and Linear Polystyrenes with High Molecular Weights, Macromolecules, 39:5180-5182, 2006.01.
376. K.Tanaka, Y.Tshchimura, K.Akabori, F.Ito, T.Nagamura, Time-and Space-resolved Fluorescene Study on Interfacial Mobility of Polymers, Appl. Phys. Lett., 89:061919-1-2, 2006.01.
377. M.Hino, M.Kitaguchi, H.Hayashida, Y.Kawabata, S.Tasaki, T.Ebisawa, D.Yamazaki, R.Maruyama, K.Tanaka, N.Torikai, R.Inoue, T.Kanaya, A Test of MIEZE-Reflectometer for study of surface and interface, Physica B, 印刷中.
378. K.Akabori, D.Baba, K.Koguchi, K.Tanaka, T.Nagamura, Relation between the Adhesion Strength and Interfacial Width for Symmetric Polystyrene Bilayers, J.Polym. Sci. B: Polym. Phys., 印刷中, 2006.08.
379. K.Akabori, K.Tanaka, A.Takahara, T.Kajiyama, T.Nagamura, Substrate Effect on Mechanical Relaxation of Polystyrene in Ultrathin Films, J.Phys. IV France, 投稿中, 2007.02.