Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Daisuke Kawaguchi Last modified date:2022.01.15

Associate Professor / Department of Applied Chemistry / Faculty of Engineering

1. Kento Kawabata, Masayasu Totani, Daisuke Kawaguchi, Hisao Matsuno, Keiji Tanaka, Two-Dimensional Cellular Patterning on a Polymer Film Based on Interfacial Stiffness, Langmuir, 10.1021/acs.langmuir.1c02776, 37, 51, 14911-14919, 2021.12.
2. Zhiwei Hao, Asieh Ghanekarade, Ningtao Zhu, Katelyn Randazzo, Daisuke Kawaguchi, Keiji Tanaka, Xinping Wang, David S. Simmons, Rodney D. Priestley, Biao Zuo, Mobility gradients yield rubbery surfaces on top of polymer glasses, Nature, 10.1038/s41586-021-03733-7, 596, 7872, 372-376, 2021.08.
3. Daisuke Kawaguchi, Kazuki Sasahara, Daiki Saito, Mitsugu Uejima, Hirotada Fujiwara, Shin Nishimura, Satoru Yamamoto, Keiji Tanaka, Molecular picture of fluoropolymer adsorption on nanocarbon materials, Polymer Journal, 10.1038/s41428-021-00528-5, 53, 12, 1469-1473, 2021.12.
4. Daisuke Kawaguchi, Keiji Tanaka, Sum Frequency Generation Spectroscopy for Understanding the Polymer Dynamics at Buried Interfaces, Spectroscopic Techniques for Polymer Characterization, 10.1002/9783527830312.ch8, 227-258, 2021.12.
5. 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, 181601-181601, 2021.05.
6. Jin-Hyeok Hong, Masayasu Totani, Daisuke Kawaguchi, Norifumi L. Yamada, Hisao Matsuno, 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, 2021.05, Surface modification of versatile polymeric materials without changing their bulk properties is one of the essential techniques for regulating their physical and chemical characteristics, and this technique can improve the functions of materials. In this study, a bottlebrush-type poly[oligo(2-ethyl-2-oxazoline) methacrylate] (P[O(Ox)(n)MA]) (n = 7 and 19) was synthesized as a surface modifier. This compound was mixed into poly(methyl methacrylate) (PMMA) as a matrix (PMMA/P[O(Ox)(n)MA]) with a weight ratio of 15%, and the aggregation state in the surface region was examined under air and aqueous environments via atomic force microscopy, contact angle measurement, angular-dependent X-ray photoelectron spectroscopy, and neutron reflectivity. The surface of the PMMA/P[O(Ox)(n)MA] films was flat at the subnanometer level and covered with the PMMA-rich phase. However, once the films contacted water, the surface was reorganized due to the migration of P[O(Ox)(n)MA]. The extent of the surface segregation was more remarkable for P[O(Ox)(7)MA] than P[O(Ox)(19)MA] due to the entropic factor. Concurrently, NIH3T3 fibroblast adhesion and serum protein adsorption on the film were more strongly suppressed for P[O(Ox)(7)MA] than P[O(Ox)(19)MA] because it formed a thicker diffused interface in the film with water..
7. 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, 1, 20914, 2020.12, AbstractA 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..
8. Hung K. Nguyen, Daisuke Kawaguchi, Keiji Tanaka, Effect of Molecular Architecture on Conformational Relaxation of Polymer Chains at Interfaces, Macromolecular Rapid Communications, 10.1002/marc.202000096, 41, 21, 2000096-2000096, 2020.11, Dynamics of polymer chains near an interface with an inorganic material are believed to strongly affect the physical properties of polymers in nanocomposites and thin films. An effect of molecular architecture on the conformational relaxation behavior of polystyrene (PS) chains at the quartz interface using sum-frequency generation spectroscopy is reported here. The relaxation dynamics of chains in direct contact with the quartz interface is slower with a star-shaped architecture than that with its linear counterpart. The extent of the delay becomes more pronounced with increasing number of arms. This can be explained in terms of the superior interfacial activity to the quartz surface for the star-shaped PS..
9. Jin-Hyeok Hong, Masayasu Totani, Daisuke Kawaguchi, Hiroyasu Masunaga, Norifumi L. Yamada, Hisao Matsuno, Keiji 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, 2020.11, We designed an amphiphilic block copolymer, poly(methyl methacrylate)-block-poly[oligo(2-ethyl-2-oxazoline) methacrylate] (PMMA-b-P[O(Ox)MA]), suitable for bioinert coating. Angular-dependent X-ray photoelectron spectroscopy and neutron reflectivity measurements revealed that the outermost surface of a dried film of PMMA-b-P[O(Ox)MA] was covered with the PMMA block-rich layer. Once the film came into contact with water, the P[O(Ox)MA] bottlebrush block was segregated toward the water interface. This structural rearrangement in the outermost region of the film resulted in the formation of the swollen oligo(oxazoline) layer with excellent bioinertness in terms of the suppression of serum protein adsorption and NIH3T3 fibroblast adhesion..
10. 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, We investigated in detail the structures in the poly(vinyl alcohol) (PVA) adsorption layers on a Si substrate, which remained on the substrate after immersing the relatively thick 30-50 nm films in hot water, by neutron reflectometry under humid conditions. For the PVA with a degree of saponification exceeding 98 mol %, the adsorption layer exhibits a three-layered structure in the thickness direction. The bottom layer is considered to be the so-called inner adsorption layer that is not fully swollen with water vapor. This may be because the polymer chains in the inner adsorption layer are strongly constrained onto the substrate, which inhibits water vapor penetration. The polymer chains in this layer have many contact points to the substrate via the hydrogen bonding between the hydroxyl groups in the polymer chain and the silanol groups on the surface of the Si substrate and consequently exhibit extremely slow dynamics. Therefore, it is inferred that the bottom layer is fully amorphous. Furthermore, we consider the middle layer to be somewhat amorphous because parts of the molecular chains are pinned below the interface between the middle and bottom layers. The molecular chains in the top layer become more mobile and ordered, owing to the large distance from the strongly constrained bottom layer; therefore, they exhibit a much lower degree of swelling compared to the middle amorphous layer. Meanwhile, for the PVA with a much lower degree of saponification, the adsorption layer structure consists of the two-layers. The bottom layer forms the inner adsorption layer that moderately swells with water vapor because the polymer chains have few contact points to the substrate. The molecular chains in the middle layer, therefore, are somewhat crystallizable because of this weak constraint..
11. 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, 2, 217-223, 2020.02.
12. 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, 52, 24, 9632-9638, 2019.12, 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 (F-L) first increased with increasing normal force (F-N) and then reached a region where the dependence of F-L on F-N was extremely subtle. That is, there exist two regimes, I and II, for the relationship between F-N and F-L. 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..
13. 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..
14. 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, The relaxation dynamics of polyisoprene (PI) and nitrile butadiene rubber (NBR) chains at the SiO2 interface were directly probed as a function of distance from the SiO2 surface using time-resolved evanescent wave-induced fluorescence anisotropy, dielectric relaxation spectroscopy, and sum-frequency generation spectroscopy. We found the presence of the dynamics gradient of chains in the interfacial region with the SiO2 surface and tried to assign it to the two kinds of adsorbed chains, namely, loosely and strongly adsorbed, at the interface. The segmental relaxation of chains in the strongly adsorbed layer at the interface could be slower than that of bulk chains by more than 10 orders..
15. 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..
16. 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 7(2) 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..
17. 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.
18. 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..
19. 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..
20. 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..
21. 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..
22. 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, 1700329-1700329, 2018.02, The rotational relaxation time ((rot)) 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 ((seg)) of the corresponding matrix polymer obtained by dielectric relaxation spectroscopy. This study here demonstrates that (seg) extrapolated to higher temperatures using the Vogel-Fulcher-Tammann law can be superimposed on (rot), 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..
23. 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..
24. 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..
25. 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..
26. 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..
27. 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.)..
28. 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..
29. 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..
30. 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..
31. Daisuke Kawaguchi, Photo-carrier formation and thermal molecular motion for semiconducting polymers, Journal of Fiber Science and Technology, 10.2115/fiber.73.p-194, 73, 5, 2017.
32. 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..
33. 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.
34. 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.
35. 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, 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..
36. Daisuke Kawaguchi, Two times studying abroad, Journal of Fiber Science and Technology, 10.2115/fiber.72.p-11, 72, 1, P11-P12, 2016.
37. 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, A better understanding of the carrier formation process in photosemiconducting polymers is crucial to design and construct highly functionalized thin film organic photodevices. Almost all studies published focus on the effect of structure on the photoinduced carrier formation process. Here, we study the dynamics of polymer chain impacts on the carrier formation process for a series of poly(3-alkylthiophene)s (P3ATs) with different alkyl side-chain lengths. The formation of polarons (P) from polaron pairs (PP) was accelerated at a temperature at which the twisting motion of thiophene rings occurs. Among all P3ATs employed, in P3AT with hexyl groups, or poly(3-hexylthiophene) (P3HT), it was easiest to twist the thiophene rings and generate P from PP. The activation energy for P formation was proportional to that of thiophene ring motion. This makes it clear that chain dynamics, in addition to the crystalline structure, is a controlling factor for the carrier formation process in photosemiconducting polymers..
38. 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, The technique of surface segregation was applied to prepare a bio-inert polymer interface. A small amount, 10 wt%, of poly(2-methoxyethyl acrylate) (PMEA), which exhibits excellent bio-inertness properties, fed into a matrix polymer was able to suppress platelet adhesion sufficiently to be of practical use. PMEA was effective because it was preferentially segregated at the outermost region of the polymer blend. Combining interfacial-sensitive analyses such as the air bubble contact angle and neutron reflectivity measurements and sum-frequency generation spectroscopy with the platelet adhesion test gives a better understanding of how the bio-inert property is expressed at the water interface..
39. 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..
40. T. Hirata, Hisao Matsuno, Daisuke Kawaguchi, N. 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, In this study, we found that the surface made of a mixture of poly(2-methoxyethyl acrylate) (PMEA) and poly(methyl methacrylate) (PMMA) exhibited excellent blood compatibility by inhibiting platelet adhesion. To obtain a better understanding of this bioinertness, the polymer/water interface was characterized by neutron reflectivity measurements and sum frequency generation spectroscopy, in conjunction with bubble contact angle measurements. Based on the results, we can say that the outermost region of the blend film was reorganized in water. When the orientation of PMEA segments at the water interface became random with increasing immersion time, the fractional amount of lower-coordinated water molecules increased at the interface. Such an interfacial structure caused the suppression of platelet adhesion..
41. M. Aoki, D. Kawaguchi, T. Ganbe, N. Sekine, K. Okamoto, K. Tanaka, Glass Transition Temperature Determination for Polymers Using Europium Complex As a Fluorescence Probe, Chemistry Letters, 10.1246/cl.150013, 44, 659-661, 2015.05.
42. Y. Oda, D. Kawaguchi, T. Hirata, N. L. Yamada, S. Kanaoka, S. Aoshima, K. Tanaka, Density Profiles of Well-Defined Poly(methyl 2-propenyl ether) (PMPE) Near Water Interface, Macromolecular Symposia, 10.1002/masy.201400031, 350, 99-104, 2015.04.
43. Y. Doi, K. Matsubara, Y. Ohta, T. Nakano, D. Kawaguchi, Y. Takahashi, A. Takano, Y. Matsushita, Melt Rheology of Ring Polystyrenes with Ultra-High Purity, Macromolecules, 10.1021/acs.macromol.5b00076, 48, in press, 2015.04.
44. T. Hirata, H. Matsuno, D. Kawaguchi, T. Hirai, N. L. Yamada, M. Tanaka, K. Tanaka, Effect of Local Chain Dynamics on a Bioinert Interface, Langmuir, 10.1021/acs.langmuir.5b00258, 31, 3661–3667, 2015.03.
45. C. Zhang, Y. Oda, D. Kawaguchi, S. Kanaoka, S. Aoshima, K. Tanaka, Dynamic-driven Surface Segregation of a Hydrophilic Component in Diblock Copolymer Films, Chemistry Letters, 10.1246/cl.140924, 44, 166-168, 2015.02.
46. D. Kawaguchi, Y. Tateishi, K. 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.
47. Y. Ogata, D. Kawaguchi, K. Tanaka, An Effect of Molecular Motion on Carrier Formation in a Poly(3-hexylthiophene) Film, Scientific Reports, 10.1038/srep08436, 5, 8436.0, 2015.01.
48. Tisato Kajiyama, Hirohiko Yakabe, Daisuke Kawaguchi, Atsushi Takahara, Keiji Tanaka, Melting behavior of thin polyethylene films, Journal of Plastic Film and Sheeting, 10.1177/8756087915594418, 31, 4, 401-413, 2015.01, Melting behavior in thin films of linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) was studied by local thermal analysis (μTA). Even in the films thinner than 100nm, the melting temperature (Tm) was successfully observed by μTA. For LLDPE, Tm decreased as the thickness became thinner than 150nm. For HDPE, Tm 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 Tm 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..
49. Y. Oda, A. Horinouchi, D. Kawaguchi, H. Matsuno, S. Kanaoka, S. Aoshima, K. Tanaka, Effect of Side-Chain Carbonyl Groups on the Interface of Vinyl Polymers with Water, Langmuir, 10.1021/la404802j, 30, 1215–1219, 2014.01.
50. Y. Ogata, D. Kawaguchi, N. L. Yamada, K. Tanaka, Multistep Thickening of Nafion Thin Films in Water, ACS Macro Letters, 10.1021/mz400322q, 2, 856-859, 2013.09.
51. Daisuke Kawaguchi, Where Does a Random-Coil Go?, Kobunshi, 62, 9, 517, 2013.09.
52. T. Nakano, D. Kawaguchi, Y. Matsushita, Anisotropic Self-Assembly of Gold Nanoparticle Grafted with Polyisoprene and Polystyrene Having Symmetric Polymer Composition, J. Am. Chem. Soc., 10.1021/ja402412q, 135, 6798−6801, 2013.04.
53. D. Kawaguchi, Direct Observation and Mutual Diffusion of Cyclic Polymers, Polymer Journal, 10.1038/pj.2012.231, 45, 783–789, 2013.01.
54. 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.
55. Daisuke Kawaguchi, Yutaka Ohta, Atsushi Takano, Yushu Matsushita, Temperature and molecular weight dependence of mutual diffusion coefficient of cyclic polystyrene/cyclic deuterated polystyrene Bilayer films, Macromolecules, 10.1021/ma3006872, 45, 16, 6748-6752, 2012.08, Temperature and molecular weight dependence of diffusion behavior of cyclic polystyrenes/Cyclic Deuterated Polystyrene Bilayer Films with high purity by secondary ion mass spectroscopy (DSIMS). Monodisperse cyclic and linear polystyrenes (c-hPS, l-hPS) and those deuterated counterparts (c-dPS, l-dPS) were used in this study. Temperature dependence for c-PS and l-PS were calculated based on the empirical equations. Taking a slight difference in molecular weights of linear and cyclic molecules into account, temperature dependence value is calculated. The temperature dependence of segmental frictional coefficient for c-PS is found to be the same as that for l-PS. The effect of small amounts of linear contaminants on the diffusion of cyclic molecules might be more significant in low molecular weight regime than in high molecular weigh. The results also show that the linear contaminants can diffuse much faster than the cyclic molecules at a same annealing temperature..
56. Atsushi Takano, Takeshi Horaiya, Fumitake Odamaki, Yoshihiko Akazawa, Yutaka Ohta, Daisuke Kawaguchi, Yoshiaki Takahashi, Yushu Matsushita, Preparation and characterization of polyisoprenes and polybutadienes having 1,2- and 3,4-linkages preferentially, polymer, 10.1016/j.polymer.2012.05.038, 53, 15, 3354-3359, 2012.07, Polyisoprenes (PI) and polybutadienes (PB) both having vinyl-type side chains preferentially were prepared and characterized. Both polymers were anionically polymerized with cumyl potassium or pottassium naphthalenide as initiators in a polar solvent, tetrahydrofuran, at low temperature. From the 1H NMR measurement, the PI contains 3,4- and 1,2-microstructures and PB does 1,2-microstructure preferentially. All the samples covering the molecular weight range of 37 k ≤ Mw ≤ 724 k for PI and 35 k ≤ Mw ≤ 197 k for PB were confirmed to have narrow molecular weight distribution. Measured glass transition temperatures, i.e., 11.0 °C for PI and -0.7 °C for PB are both considerably high compared with those of 1,4-microstructure-rich analogues. Intrinsic viscosity measurements in 1,3-dioxane for PI and 2-octanol for PB were carried out, and the segment lengths of the 3,4-/1,2-rich PI and 1,2-rich PB were estimated to be 0.60 nm and 0.59 nm, which are both considerably shorter than the values for two polydienes having 1,4-microstructures preferentially, i.e., 0.66 nm for both 1,4-rich PI and PB. Furthermore plateau moduli of both polymers are determined by dynamic viscoelastic measurements..
57. A. Takano, Y. Ohta, K. Masuoka, K. Matsubara, T. Nakano, A. Hieno, M. Itakura, K. Takahashi, S. Kinugasa, D. Kawaguchi, Y. Takahashi, Y. Matsushita, Radii of Gyration of Ring-Shaped Polystyrenes with High Purity in Dilute Solutions, Macromolecules, 10.1021/ma202031w, 45, 369–373, 2012.01.
58. D. Kawaguchi, A. Nelson, Y. Masubuchi, J. P. Majewski, N. Torikai, N. L. Yamada, Siti Sarah A. R., A. Takano, Y. Matsushita, Precise Analyses of Short-Time Relaxation at Asymmetric Polystyrene Interface in Terms of Molecular Weight by Time-Resolved Neutron Reflectivity Measurements, Macromolecules, 10.1021/ma201717e, 44, 9424–9433, 2011.12.
59. S.S.A. Rahman, D. Kawaguchi, Y. Matsushita, Microphase-Separated Structures of Poly(4-tert-butylstyrene-block-4-tert- butoxystyrene) Upon Gradual Changes in Segregation Strength through Hydrolysis Reaction, Macromolecules, 10.1021/ma102440a, 44, 2799-2807, 2011.03.
60. N. Torikai, N. L. Yamada, D. Kawaguchi, A. Takano, Y. Matsushita, E. Watkins, J. P. Majewski, Depth Distribution of Different Solvents in a Phase-Separated Block Copolymer Thin Film, J. Phys.: Conf. Ser., 10.1088/1742-6596/272/1/012027, 272, 012027, 2011.02.
61. S.S.A. Rahman, D. Kawaguchi, Y. Matsushita, Monomer Sequence of Partially Hydrolyzed Poly(4-tert-butoxystyrene) and Morphology of Diblock Copolymers Composing This Polymer Sequence as One Block, Polymer, 10.1016/j.polymer.2010.11.010, 52, 164-171, 2011.01.
62. Jae Hyun Kim, Martin Y.M. Chiang, Daisuke Kawaguchi, Naomi Eidelman, Christopher M. Stafford, Chang Kwon Moon, Combinatorial library designs for quantifying thin film adhesion via the edge delamination test, Journal of Physics D: Applied Physics, 10.1088/0022-3727/44/3/034003, 44, 3, 2011.01, We have demonstrated a combinatorial thin film library design for investigating the adhesion between film and substrate as measured by the edge delamination test. This library design allows rapid screening of critical parameters that control thin film reliability and bond strength in films and coatings. Specifically, our library design was aimed at quantifying the effect of film thickness and composition on the interfacial integrity between the film and underlying substrate by applying thermal stress. To create the combinatorial library, a single specimen was fabricated having a thickness gradient of an epoxy film on glass or silicon substrates. After sectioning the film into individual squares, a temperature gradient was applied orthogonal to the thickness gradient to induce debonding events where the adhesion is below a critical value. In addition, another combinatorial library was carried out using the epoxy films with concentration gradient and constant thickness, and applying a constant temperature. The combined results clearly demonstrate that our combinatorial library design and approach provide a large parameter space for accurately and reproducibly mapping the interfacial integrity and bond strength of film/substrate systems..
63. 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..
64. Yutaka Ohta, Yuuki Kushida, Daisuke Kawaguchi, Yushu Matsushita, Atsushi Takano, Preparation, Characterization, and Nanophase-Separated Structure of Catenated Polystyrene−Polyisoprene, Macromolecules, 10.1021/ma7028852, 41, 11, 3957-3961, 2008.06, A catenated copolymer consisting of cyclic polystyrene (PS) with short poly(2-isopropenylnaphthalene) (PIPN) segments and cyclic polyisoprene (PI) were prepared by living anionic polymerization. The molecular weight of catenated copolymer is 37 kDa. Naphthalene side groups attached to the PIPN segments in the cyclic P(IPN-b-S) were radical-anionized by a reaction with potassium in THF, and telechelic PI was successfully cyclized by a pair of coupled reactions at two close radical-anionized sites on the cyclic chain under dilute conditions. Formation of the catenated copolymer consisting of cyclic P(IPN-b-S) and cyclic PI was confirmed by size-exclusion chromatography using a UV detector with a wavelength of 320 nm for preferential detection of naphthalene moieties. After isolation of the catenated copolymer by fractionation, it was confirmed by transmission electron microscopy that the topologically linked polymers exhibit a nanophase-separated structure in bulk..
65. D. Kawaguchi, A. Takano, Y. Matsushita, Molecular Characterization and Interdiffusion of Ring-shaped Polystyrenes and Their Derivatives, AES Technical Reviews Part A, 1, 63-70, 2008.04.
66. A. Takano, W. Kawashima, S. Wada, K. Hayashida, S. Sato, S. Kawahara, Y. Isono, M. Makihara, N. Tanaka, Daisuke Kawaguchi, Y. Matsushita, Composition dependence of nanophase-separated structures formed by star-shaped terpolymers of the A1.0B1.0CX type, Journal of Polymer Science, Part B: Polymer Physics, 10.1002/polb.21241, 45, 16, 2277-2283, 2007.08, Several hierarchical nanophase-separated structures have been observed for a series of ABC star-shaped terpolymers by transmission electron microscopy (TEM) and electron computerized tomography (3D-TEM). The seven terpolymers synthesized are composed of polyisoprene (I), polystyrene (S), and poly(2-vinylpyridine) (P), their volume fraction ratios of I:S:P are 1:1:X, where X equals 0.2, 0.4, 0.7, 1.2, 1.9, 3.0, and 4.9, respectively, and additional four samples were prepared by blending each two parent terpolymers. From morphological observation by TEM and tomography, a terpolymer with X of 0.2 shows lamellar structure with spheres at the interface, those with X ranging from 0.4 to 1.9 show cylindrical structures with twodimensional tiling, while those with X of 3.0 and 4.9 show hierarchical cylinders-inlamella structure. Two the other terpolymer samples with X of 7.9 and 10 were produced by blending a P homopolymer with the terpolymer I1.0S1.0P4.9, and they both exhibited columnar piled disk cylinders in P matrix. From the comparison of the present results with the predictions by the Monte-Carlo simulation, it was confirmed that the observed nanophase-separated structures of the ISP star-shaped terpolymers are mostly in good agreement with the prediction..
67. Daisuke Kawaguchi, Atsushi Takano, Yushu Matsushita, Characterization of cyclic polystyrene with high molecular weight and its interdiffusion behavior, KOBUNSHI RONBUNSHU, 10.1295/koron.64.397, 64, 7, 397-405, 2007.07, In this paper, synthesis and characterization of cyclic polystyrenes (c-PS) including the structural feature of one of the derivatives and interdiffusion of c-PS are described. The cyclic structure of poly (styrenesulfonate), which was obtained by sulfonation of c-PS, was directly confirmed by atomic force microscopic observation. The purities of c-PS, evaluated by high performance liquid chromatography, were higher than 95%. The time-dependent interfacial thickness of a cyclic polystyrene (c-hPS)/its deuterated counterpart (c-dPS) bilayer film and that of a linear polystyrene (1-hPS)/its deuterated counterpart (1-dPS) bilayer film was investigated by dynamic secondary ion mass spectrometry (DSIMS) and neutron reflectivity (NR) measurement. The diffusion constant of c-PS is significantly larger than that of the corresponding linear one. This can be explained in terms of weaker topological constraint due to the lesser entanglement of c-PS..
68. N. Torikai, N. L. Yamada, D. Kawaguchi, A. Takano, Y. Matsushita, E. Watkins, J. P. Majewski, H. Okuda, In-situ reflectometry observation on structural changes of thin self-assembled block copolymer films, Journal of Physics: Conference Series, 10.1088/1742-6596/83/1/012028, 83, 1, in press, 2007.06, The structural changes induced by solvent contact or heating were observed for thin spin-coated polystyrene-block-poly(2-vinylpyridine) diblock copolymer (PS-P2VP) films using in-situ neutron reflectivity and grazing-incidence small-angle X-ray scattering (GISAXS) techniques. The lamellarly-ordered PS-P2VP film showed some structural changes in contact with water though it is a poor solvent for both the component polymers, while the original structure was recovered after drying the film. When toluene was used as a selectively good solvent for PS, the thin film was dissolved into the solvent. On the other hand, the thin as-prepared PS-P2VP film with spherical microdomains exhibited laterally a pair of scattering spots symmetrical relative to the specular reflection ridge in the GISAXS pattern, indicating the existence of some lateral structural correlation in the film. On a temperature jump up to 200 °C, these two scattering spots started to disappear around the glass transition temperature, and then almost completely vanished at 200 °C unexpectedly though the PS-P2VP used here should be kept in the strong-segregation state. The spherical structure could be completely disordered or kept ordered but with lateral distortion in its orientation. Being cooled down to a room temperature again, the two scattering spots were recovered, and became more intense with their position shifting slightly to lower QY-region than before heating due to the improvement in ordering. © 2007 IOP Publishing Ltd..
69. Daisuke Kawaguchi, Keiji Tanaka, Naoya Torikai, Atsushi Takahara, Tisato Kajiyama, Surface and Interfacial Segregation in Blends of Polystyrene with Functional End Groups and Deuterated Polystyrene, Langmuir, 10.1021/la700418j, 23, 13, 7269-7275, 2007.06, The effect of chain-end chemistry on surface and interfacial segregation in symmetric blends of polystyrene (hPS)/deuterated polystyrene (dPS) has been investigated by X-ray photoelectron and secondary ion mass spectroscopy in conjunction with neutron reflectivity measurements. alpha,omega-Fluoroalkyl- and alpha,omega-carboxy-terminated polystyrenes (alpha,omega-hPS(R(f))(2) and alpha,omega-hPS(COOH)(2)) were used as end-functionalized polymers; the former possesses chain ends with lower surface energies, and the latter possesses higher surface energies compared with that of the main chain. In the case of an alpha,omega-hPS(R(f))(2)/dPS blend film, alpha,omega-hPS(R(f))(2) was enriched at the surface owing to the surface localization of the R(f) groups, although the surface energy of the hPS segments was slightly higher than that of the dPS ones. On the contrary, in the case of an alpha,omega-hPS(COOH)(2)/dPS blend film, dPS was preferentially segregated at the surface. This may be due to a surface depletion of COOH ends and an apparent molecular weight increase of alpha,omega-hPS(COOH)(2) produced by a hydrogen-bonded intermolecular association of COOH ends in addition to the surface energy difference between hPS and dPS segments. Interestingly, both R(f) and COOH chain ends were partitioned to the substrate interface for the alpha,omega-hPS(R(f))(2)/dPS and alpha,omega-hPS(COOH)(2)/dPS blend films, resulting in the segregation of the hPS component at the substrate interface for both blends. The results presented imply that surface and interfacial segregation in polymer blends could be regulated by incorporating functional groups into the end portions of one component..
70. Daisuke Kawaguchi, Takashi Nishu, Atsushi Takano, Yushu Matsushita, Direct Observation of an Isolated Cyclic Sodium Poly(styrenesulfonate) Molecule by Atomic Force Microscopy, Polymer Journal, 10.1295/polymj.pj2006155, 39, 3, 271-275, 2007.03.
71. Atsushi Takano, Yuuki Kushida, Kayoko Aoki, Keisuke Masuoka, Kenichi Hayashida, Donghyun Cho, Daisuke Kawaguchi, Yushu Matsushita, HPLC Characterization of Cyclization Reaction Product Obtained by End-to-End Ring Closure Reaction of a Telechelic Polystyrene, Macromolecules, 10.1021/ma062496w, 40, 3, 679-681, 2007.02, Cyclization reaction product synthesized by the end-to-end ring closure reaction of a telechelic polystyrene with molecular weight of 38K in extremely dilute conditions was carefully characterized by using two kinds of HPLC techniques, that is, liquid chromatography at the critical condition (LCCC) and size exclusion chromatography (SEC). First, the cyclization reaction product was coarsely separated into linear species and cyclic ones by LCCC; second, each fraction was further separated by high-resolution SEC. It was found from the HPLC analyses that the cyclization reaction product contains both linear and cyclic condensation products. Furthermore, dimeric, trimeric, and more multimeric cyclic molecules with reasonable abundance were identified as well as the monomeric cyclic molecule with high yield, as much as 50%, in the cyclic products..
72. N. Torikai, N. L. Yamada, D. Kawaguchi, A. Takano, Y. Matsushita, E. Watkins, J. P. Majewski, H. Okuda, In-Situ Reflectometry Observation on Structural Changes of Thin Self-Assembled Block Copolymer Films, J. Phys. Conf. Ser., 10.1088/1742-6596/83/1/012028, 83, 012028, 2007.01.
73. Naoya Torikai, Atsushi Noro, Masatoshi Okuda, Fumitake Odamaki, Daisuke Kawaguchi, Atsushi Takano, Yushu Matsushita, Neutron Reflection Studies on Lamellar Microphase-Separated Structures of Two-Component Block Copolymers with Composition Distribution, Physica B: Condensed Matter, 10.1016/j.physb.2006.05.303, 385-386, 709-712, 2006.11, Segmental distribution of polystyrene blocks in lamellar microphase-separated poly(styrene-block-2-vinylpyridine) (SP) with wide composition distribution was investigated by neutron reflectivity measurements using deuterium-labeled polymers. Block copolymers with wide composition distribution were produced by mixing three monodispersed parent block copolymers, which were synthesized by an anionic polymerization method to have the same total molecular weight but with different volume fractions. The block copolymer blends whose overall S/P ratio is 0.5/0.5 were found to form a uniform lamellar structure, where lamellae were highly oriented along the direction parallel to the film surface and the interfacial thickness was evaluated as 40 A. It was clarified that a shorter block chain in the microdomain is localized at the domain boundary, while a longer one has a peak at the center of microdomain in its segmental distribution profile. (c) 2006 Elsevier B.V. All rights reserved..
74. 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.
75. Christopher M. Stafford, Jae Hyun Kim, Daisuke Kawaguchi, Gareth Royston, Martin Y.M. Chiang, Probing the interfacial adhesion strength in compositional libraries of epoxy films, Combinatorial Methods and Informatics in Materials Science Materials Research Society Symposium Proceedings, 894, 129-137, 2006, We are developing a measurement platform, based on the edge delamination test geometry, geared towards combinatorial and high-throughput (C&HT) assessment of interfacial adhesion and reliability of epoxy films bonded to a rigid substrate. A critical parameter space to be explored is composition of the epoxy formulation. We have constructed an automated mixing and deposition system for creating discrete and continuous gradients in composition of viscous epoxy formulations. By dicing the combinatorial library into a contiguous discrete sample array, the interfacial adhesion strength can be deduced from the critical stress required to debond each film cell from the substrate. These results can be used to predict the adhesion reliability of epoxy formulations as a function of composition and applied stress..
76. D. Cho, K. Masuoka, K. Koguchi, T. Asari, D. Kawaguchi, A. Takano, Y. Matsushita, Preparation and Characterization of Cyclic Polystyrenes, Polymer Journal, 10.1295/polymj.37.506, 37, 506-511, 2005.07.
77. Masashi Harada, Takahisa Suzuki, Masayuki Ohya, Daisuke Kawaguchi, Atsushi Takano, Yushu Matsushita, Naoya Torikai, Interfacial profiles of miscible poly(4-trimethylsilylstyrene)/polyisoprene bilayer films, Journal of Polymer Science Part B: Polymer Physics, 10.1002/polb.20442, 43, 12, 1486-1494, 2005.06, Compositional profiles of bilayer films in the direction normal to the interfaces have been investigated by neutron reflectivity measurements and analyzed with mean field theory. The bilayer films were prepared with poly(4-trimethylsilylstyrene) (PTMSS) and polyisoprene (PI), which constitute a miscible polymer pair and whose blends show phase separation at the lower critical solution temperature (LCST) by heating. Because we can accurately control the degree of polymerization of component polymers and can adjust the Flory-Huggins interaction parameter, chi, with the temperature, Tau, according to the relationship chi = 0.027-9.5/T, the phase behavior and the interfacial structure of PTMSS and PI are predictable by mean field theory. When the bilayer films of PTMSS and PI were set at 90 degrees C, which is a temperature below the LCST, diffusion at the interface was observed, and the original interface disappeared in several hours; this supports the idea that the polymer pair is miscible. No clear interfaces were identified below the LCST, whereas broad interfaces, compared with that of the strong segregation pairs, were observed above the LCST. The compositions of each layer are consistent with that of the coexisting phase in the polymer blends, and the interfacial widths agree well with the theoretical prediction considering the effect of capillary waves. In addition, all annealed films have a thin surface layer of PTMSS corresponding to surface segregation induced by the lower surface energy of PTMSS (with respect to that of PI). Thus, the interfacial profiles of PTMSS/PI bilayer films have been totally prospected in the framework of mean field theory. (c) 2005 Wiley Periodicals, Inc..
78. Masashi Harada, Masayuki Ohya, Takahisa Suzuki, Daisuke Kawaguchi, Atsushi Takano, Yushu Matsushita, Preparation and phase behavior of poly(4-trimethylsilylstyrene)-block-polyisoprene, Journal of Polymer Science Part B: Polymer Physics, 10.1002/polb.20415, 43, 10, 1214-1219, 2005.05, Three poly(4-trimethylsilylstyrene)-block-polyisoprenes (TIs), the molecular weights of which were 82,000, 152,000 and 291,000 (TI-82K, TI-152K, and TI-291K), were synthesized by sequential anionic polymerizations. The component polymers were a miscible pair that presented a lower critical solution temperature phase diagram if blended. The TI phase behavior was investigated with transmission electron microscopy. The order-disorder transition could be observed at a temperature between 200 degrees C (the ordered state) and 150 degrees C (the disordered state) for the block copolymer TI-152K. The block copolymer TI-82K presented the disordered state at 200 degrees C, whereas TI-291K was in the ordered state at 150 degrees C. With the Flory-Huggins interaction parameter between poly(4-trimethylsilylstyrene) and polyisoprene, which was evaluated by small-angle neutron scattering for the block copolymers, the TI phase behavior could be reasonably explained by mean-field theory. (c) 2005 Wiley Periodicals, Inc..
79. M. Harada, M. Ohya, T. Suzuki, D. Kawaguchi, A. Takano, Y. Matsushita, Preparation and Phase Behavior of Poly(4-trimethylsilylstyrene)-block-Polyisoprene, J. Polym. Sci. Part B-Polym. Phys., 10.1002/polb.20415, 43, 1214-1219, 2005.03.
80. Tisato Kajiyama, Daisuke Kawaguchi, Keiji Tanaka, Surface mobility in monodisperse polystyrene films, Macromolecular Symposia, 10.1002/masy.200351111, 201, 1, 95-102, 2003.10, 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..
81. Keiji Tanaka, Daisuke Kawaguchi, Yasuyuki Yokoe, Tisato Kajiyama, Atsushi Takahara, Seiji Tasaki, Surface segregation of chain ends in α,ω-fluoroalkyl-terminated polystyrenes films, Polymer, 10.1016/s0032-3861(03)00391-4, 44, 15, 4171-4177, 2003.07, alpha,omega-Fluoroalkyl-terminated polystyrenes (alpha,omega-PS(R-f)(2)) with various molecular weights were synthesized by an anionic polymerization. Then, chain end distribution in the surface region of the alpha,omega-PS(R-f)(2) films was studied by angular-dependent X-ray photoelectron spectroscopy in conjunction with neutron reflectivity. The alpha,omega-PS(R-f)(2) films annealed under vacuum exhibited surface localization of chain ends. Since the fluoroalkyl chain ends possess a lower surface free energy compared with the main chain part, they energetically prefer to partition to the surface. The extent to which the chain ends were segregated at the surface was examined as a function of molecular weight. Also, it was presented how surface orientation of the fluoroalkyl end groups was dependent on molecular weight. On the other hand, no segregation of the chain ends was observed at the surface of the alpha,omega-PS(R-f)(2) film annealed in boiled water. This is because the chain ends with a lower surface free energy tend to stay away from the higher energy medium of the boiled water. This result reveals that the surface concentration of chain ends can be regulated by selecting an appropriate annealing condition based on surface thermodynamics. (C) 2003 Elsevier Science Ltd. All rights reserved..
82. 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..
83. T. Kajiyama, N. Satomi, Y. Yokoe, D. Kawaguchi, K. Tanaka, A. Takahara, Effect of End Group Chemistry on Surface Molecular Motion of Monodisperse Polystyrene Films, Macromol. Symp., 10.1002/1521-3900(200010)159:1<35::AID-MASY35>3.0.CO;2-R, 159, 35-42.
84. T. Kajiyama, D. Kawaguchi, A. Sakai, N. Satomi, K. Tanaka, A. Takahara, Determination Factors on Surface Glass Transition Temperatures of Polymeric Solids, High Performance Polym., 10.1088/0954-0083/12/4/314, 12, 587-597, 2000.12.
85. A. Takahara, K. Tanaka, D. Kawaguchi, S. Tasaki, M. Takeda, N. Torikai, and T. Kajiyama, Neutron Reflectivity Study of Surface and Interfacial Structure in Polymer Thin Films, Trans. MRS-J., 28, 81-84, 2003.01.
86. A. Takahara, D. Kawaguchi, K. Tanaka, M. Tozu, T. Hoshi, T. Kajiyama, Analysis of surface composition of isotopic polymer blend based on time-of-flight secondary ion mass spectroscopy, Applied Surface Science, 10.1016/s0169-4332(02)00748-1, 203-204, 538-540, 2003.01, Surface chemical composition of blend composed of monodisperse polystyrene (hPS) with the number-average molecular weight, M-n, of 19.7k and deuterated monodisperse polystyrene (dPS) with M-n of 847k was analyzed based on time-of-flight secondary ion mass spectroscopy (ToF-SIMS). Although hPS possess higher surface free energy than dPS, ToF-SIMS revealed that hPS was preferentially segregated at the outermost surface of the blend films with various compositions. The surface segregation of hPS can be explained in terms of the molecular weight disparity for both components, i.e., an entropic effect. (C) 2002 Elsevier Science B.V. All rights reserved..
87. Daisuke Kawaguchi, Keiji Tanaka, Tisato Kajiyama, Atsushi Takahara, Seiji Tasaki, Mobility Gradient in Surface Region of Monodisperse Polystyrene Films, Macromolecules, 10.1021/ma025667f, 36, 4, 1235-1240, 2003.02, Surface mobility in polystyrene (PS) films was studied using (PS/deuterated PS) bilayer films, which were prepared by attaching original two surfaces together. Time evolution of the bilayer interface at various temperatures was examined by dynamic secondary ion mass spectroscopy in conjunction with neutron reflectivity. When the bilayer was annealed at a temperature above bulk glass transition temperature, T-g(b), the interfacial thickening was well expressed by the context of Fickian diffusion. On the other hand, in the case of an annealing temperature above surface glass transition temperature, T-g(s), and below T-g(b), the interface monotonically thickened with the time at first and then turned to be independent. This means that chains went across the "mobile" interface and then reached the "dead" bulk region in which the diffusivity should be frozen. Hence, it was claimed that chains could diffuse discernibly in the surface region even at a temperature lower than the T-g(b). On the basis of temperature and molecular weight dependences of quasi-equilibrium interfacial thickness after a sufficiently long time, a possible model of mobility gradient in the surface region was proposed..
88. Daisuke Kawaguchi, Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Surface Mobile Layer of Polystyrene Film below Bulk Glass Transition Temperature, Macromolecules, 10.1021/ma010012k, 34, 18, 6164-6166, 2001.08.