Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Ken Kojio Last modified date:2020.10.01

Associate Professor / Department of Applied Molecular Chemistry / Institute for Materials Chemistry and Engineering


Papers
1. Ya Ting Hsieh, Shuhei Nozaki, Makoto Kido, Kazutaka Kamitani, Ken Kojio, Atsushi Takahara, Crystal polymorphism of polylactide and its composites by X-ray diffraction study, Polymer Journal, 10.1038/s41428-020-0343-8, 52, 7, 755-763, 2020.07, Polylactide (PLA) exhibits various types of crystal modifications depending on the preparation conditions, including the components. To solve the open question, a reliable calculation method for crystallinity, crystal forms, and composition in neat PLA and PLA composites was developed on the basis of temperature-dependent synchrotron wide-angle X-ray diffraction results. The relative composition of amorphous, α-form, and α’-form phases of PLA and its composites filled with halloysite nanotubes during heating was successfully obtained. It was found that only 47–56% of α’-form crystals transform into α-form crystals during a 2 °C/min heating process for PLA with a molecular weight of 54,300 g/mol. The loading of halloysite nanotubes decreases the cold crystallization and starting transition (α’ crystals transform into α-form crystals) temperatures of PLA. The crystallinity and the main diffraction peak intensity as a function of temperature were also analyzed. These results suggest that the α’-to-α form transition is a solid-solid phase transition..
2. Chao Hung Cheng, Shiori Masuda, Shuhei Nozaki, Chigusa Nagano, Tomoyasu Hirai, Ken Kojio, Atsushi Takahara, Fabrication and Deformation of Mechanochromic Nanocomposite Elastomers Based on Rubbery and Glassy Block Copolymer-Grafted Silica Nanoparticles, Macromolecules, 10.1021/acs.macromol.9b02031, 53, 11, 4541-4551, 2020.06, The strength of silica-based mechanochromic nanocomposites was improved by a novel nanocomposite synthesized by grafting poly(butyl acrylate) (PBA)-b-poly(methyl methacrylate) (PMMA) from silica nanoparticles (SiNP). Samples with different PMMA/PBA ratios were prepared to clarify the effect of the rubbery/glassy block copolymer ratios on the mechanical properties of the nanocomposites. The nanocomposites formed a face-centered cubic paracrystal-like structure and exhibited structural color. Time-resolved ultrasmall-angle X-ray scattering was carried out to investigate the structural evolution of the nanocomposites by uniaxial and biaxial mechanical deformation. Changes in color and mechanochromic properties were observed at varying distances between the particles by mechanical deformation. The nanocomposites exhibited elastic and plastic properties and became more rubber-like as the rubbery PBA weight ratio increased. The polymer brush deformed into a prolate spheroid by uniaxial stretching, and the distance between SiNP decreased in the direction perpendicular to elongation, which resulted in the color change by mechanical deformation. Moreover, the distance between SiNP increased isotropically by biaxial stretching. The polymer brush was elongated isotropically toward the in-plane direction and deformed into an oblate spheroid..
3. Ken Kojio, Shuhei Nozaki, Atsushi Takahara, Satoshi Yamasaki, Influence of chemical structure of hard segments on physical properties of polyurethane elastomers
a review, Journal of Polymer Research, 10.1007/s10965-020-02090-9, 27, 6, 2020.06, Hard segments of polyurethanes (PUs) are generally formed from diisocyanate and diol. Diol can be replaced with triol and thiol. These chemical structures of hard segments strongly affect not only a microphase separated structure but mechanical properties of resultant PUs. In this review, we focus on the relationship between chemical structure like symmetry and bulkiness of diisocyanate and mechanical properties of PU. Then, influence of hard segment content, incorporation of 1,1,1-trimethylol propane with trifunctional groups, and alkyldithiol was reviewed mainly on trans-1,4-bis(isocyanatomethyl) cyclohexane-poly(oxytetramethylene) glycol-based PU..
4. Manus Sriring, Adun Nimpaiboon, Sirirat Kumarn, Keiko Higaki, Yuji Higaki, Ken Kojio, Atsushi Takahara, Chee Cheong Ho, Jitladda Sakdapipanich, Film formation process of natural rubber latex particles
roles of the particle size and distribution of non-rubber species on film microstructure, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2020.124571, 592, 2020.05, Natural rubber (NR) films from various mixing ratios of large- (LRP) and small rubber particles (SRP) were prepared through latex and solution casting methods. Film-forming behaviours of the resulting films were investigated by monitoring their surface characteristics using atomic force microscopy (AFM). When the SRP portion was higher, the surface of the latex-cast films was found to be smoother as smaller particles protruded out of the surface less than larger ones did. AFM phase micrographs revealed a hexagonal shape of packed rubber particles (RPs) of the LRP film, while the RPs in the other samples were sphere-like. After aging under ambient conditions, the packed RPs were flattened while retaining their RP boundaries, creating a supporting framework within the rubber matrix. On the contrary, when the rubber film was cast from a toluene solution, the characteristic of RP boundaries disappeared and became aggregates of the membrane components on the film surface. The latex-cast films performed much better in mechanical strength than the solution-cast films did due to the destruction of the supporting framework arisen from the non-rubber components at the RP boundaries of the solution-cast film. An inhomogeneous density distribution produced by the non-rubber aggregates in the latex-cast films was observed in small angle X-ray scattering measurements..
5. Ken Kojio, Tomoko Kajiwara, Saburo Yamamoto, Aya Fujimoto, Kento Fukada, Chigusa Nagano, Shiori Masuda, Chao Hung Cheng, Shuhei Nozaki, Kazutaka Kamitani, Atsushi Takahara, Direct visualization of the molecular orientation and microstructure of glassy transparent polymers after the scratch test based on optical microscopy and X-ray scattering, polymer, 10.1016/j.polymer.2019.121773, 181, 2019.10, The scratch test was conducted for polycarbonate (PC) and poly(methyl methacrylate) (PMMA) with a load-progressive mode. Changes in the molecular aggregation structure of PC and PMMA induced by the scratch test were investigated based on polarized optical microscopic observation and small-angle X-ray scattering (SAXS) measurement. The scratching coefficient of friction (SCOF), the ratio of tangential load to normal load, of PC was much larger than that of PMMA. The width and depth of the damage on the scratch path was increased monotonically with the increase in the normal load. Hardness obtained by nanoindentation and microindentation tests were similar to those with SCOF, indicating that compression resistance mainly governs the scratch properties. The polarized optical microscopic images revealed that molecules were oriented from the edge to the center of the scratch path at a certain acute angle for both PC and PMMA. SAXS measurement revealed that microfibrils were formed along the direction of stress for PC..
6. Ken Kojio, Aya Fujimoto, Tomoko Kajiwara, Chigusa Nagano, Shiori Masuda, Chao Hung Cheng, Shuhei Nozaki, Kazutaka Kamitani, Hirohmi Watanabe, Atsushi Takahara, Advantages of bulge testing and rupture mechanism of glassy polymer films, polymer, 10.1016/j.polymer.2019.121632, 179, 2019.09, The advantages of bulge testing as a method of mechanical property analysis for polymer films was described. Deformation and rupture mechanisms of glassy polymer films during bulge testing were investigated by in situ molecular aggregation structure analyses. Heat-pressed polycarbonate (PC, weight-average molecular weight (Mw) = 38k) and poly(methyl methacrylate) (PMMA, Mw = 70k and 1.2 M (PMMA-70k and PMMA-1.2 M)) films were employed as transparent glassy polymers. Evaluations of molecular aggregation structures during bulge testing were conducted by polarized high-speed camera observation and wide-angle X-ray diffraction (WAXD) measurements. PC and PMMA-1.2 M films showed a yield point in their stress-strain curves, indicating ductility, while PMMA-70k film showed brittleness. WAXD measurements revealed that the distances between the main chains slightly increased with increasing strain. With increasing film strain above the yield point, a craze-like morphology with thinning of the film was seen for the PC film, likely due to the flexible PC molecules. Although it is difficult for PMMA molecules to orient along applied stress, a transition to the thinner state with the formation of wrinkled structures occurred for the PMMA-1.2 M film above the yield point. The transition to the thinner state, which corresponds to a discontinuous decrement of the cross-section area by deformation, might be categorized as two-dimensional crazing and/or shear deformation. PMMA-70k did not show such behavior because of the small number of entanglements. The use of a small amount of films in terms of thickness and size and the capability of observation of the entire film were given as advantages of the bulge test..
7. Rahmawati Rahmawati, Shiori Masuda, Chao Hung Cheng, Chigusa Nagano, Shuhei Nozaki, Kazutaka Kamitani, Ken Kojio, Atsushi Takahara, Naoki Shinohara, Kazuki Mita, Kiminori Uchida, Satoshi Yamasaki, Investigation of Deformation Behavior of Thiourethane Elastomers Using in Situ X-ray Scattering, Diffraction, and Absorption Methods, Macromolecules, 10.1021/acs.macromol.9b00982, 52, 18, 6825-6833, 2019.09, The deformation behavior of polythiourethane (PTU) elastomers was investigated using in situ small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and X-ray absorption fine structure (XAFS) methods. Two PTUs were prepared from poly(oxytetramethylene) glycol, 1,4-bis(isocyanatomethyl) cyclohexane, and 1,4-butanedithiol (PTU-B) or 1,5-pentanedithiol (PTU-P). The effect of methylene length of the chain extender on molecular aggregation structure of PTU during the elongation process was evaluated. SAXS measurement revealed that the spacing of hard segment domains of PTUs increased and decreased in the directions parallel and perpendicular to the elongation direction and showed a constant value of strain above 2. The strain calculated from the spacing of the hard segment domains for PTU-B was larger than that for PTU-P, suggesting that well-developed hard segment domains were formed for PTU-B. WAXD measurement showed that strain-induced crystallization of the soft segment occurred at around the strain of 2. XAFS measurement showed that at the strain of 2 or 3, atoms in the vicinity of sulfur became more ordered, which is confirmed by the decrement of the extended XAFS Debye-Waller factor. It seems reasonable from these SAXS, WAXD, and XAFS results that the hard segment domains orientation occurred for both PTUs during the deformation process, followed by strain-induced crystallization of the soft segment. In addition, PTU-B exhibits more ordered hard segment domains that maintain their aggregation structure upon uniaxial deformation in comparison with PTU-P..
8. Manus Sriring, Adun Nimpaiboon, Nattanee Dechnarong, Sirirat Kumarn, Yuji Higaki, Ken Kojio, Atsushi Takahara, Chee Cheong Ho, Jitladda Sakdapipanich, Pre-Vulcanization of Large and Small Natural Rubber Latex Particles
Film-Forming Behavior and Mechanical Properties, Macromolecular Materials and Engineering, 10.1002/mame.201900283, 304, 9, 2019.09, The pre-vulcanized large rubber particle (LRP) and small rubber particle (SRP) latices are independently prepared to investigate their film-forming process and mechanical properties after being cast into films. The surface morphologies and roughness of both LRP and SRP films are found to be dependent on crosslink densities. The networks inside each rubber particle (RP) restrict particle deformation resulting in residual contour of RP within the film surface. For highly crosslinked RP, the collapse of the top surface of the RPs in the LRP films appears to create many “crater-like” structures within the film surfaces, while they present only protruding particles within the SRP and blend films. This seems to indicate that LRPs are easier to coalesce and form film than SRPs. Additionally, dynamic and mechanical properties and strain-induced crystallization (SIC) behaviors of the latex films, are effectively enhanced after pre-vulcanization. The pre-vulcanized LRP films perform better tensile properties and SIC than the SRP can..
9. Hitoshi Shimamoto, Chao Hung Cheng, Kazutaka Kamitani, Ken Kojio, Yuji Higaki, Atsushi Takahara, Nanocomposite elastomers composed of silica nanoparticles grafted with a comb-shaped copolymer Brush, Macromolecules, 10.1021/acs.macromol.9b00927, 52, 15, 5963-5970, 2019.08, Nanocomposites composed of monodisperse silica nanoparticles (SiNPs) modified with an elastic comb-shaped block copolymer brush were produced for the first time. Comb-shaped polymer brushes consisting of glassy poly(methyl methacrylate) branches and a rubbery poly(butyl acrylate) backbone were grafted from 100 nm diameter SiNPs by surface-initiated atom transfer radical polymerization. The comb-shaped polymer brush-grafted SiNPs produced self-standing films with a face-centered cubic ordered lattice structure via solvent-casting. The composite films showed rubber elasticity because of the interparticle rubbery polymer brush boundary phase. The ordered lattice exhibited significant alignment and distortion in response to the macroscopic film strain, and then reproduced the initial ordered lattice after unloading. ©.
10. Shuhei Nozaki, Shiori Masuda, Chao Hung Cheng, Chigusa Nagano, Kazutoshi Yokomachi, Kazutaka Kamitani, Kohki Aoyama, Hiroyasu Masunaga, Ken Kojio, Atsushi Takahara, Direct Evaluation of Local Dynamic Viscoelastic Properties of Isotactic Polypropylene Films Based on a Dynamic μ-Beam X-ray Diffraction Method, ACS Macro Letters, 10.1021/acsmacrolett.8b00994, 8, 2, 218-222, 2019.02, The local mechanical properties of crystalline polymer were evaluated using synchrotron radiation X-ray diffraction with 10 μm lateral resolution. A nonoriented isotactic polypropylene (iPP) film with isolated spherulites in a crystallized matrix was used as a model sample. In situ wide-angle X-ray diffraction (WAXD) measurement was performed on the iPP film using a microbeam synchrotron radiation X-ray under sinusoidal strain. The lattice spacing of the crystal planes increased and decreased in response to the applied sinusoidal strain. Local dynamic viscoelastic functions (dynamic storage and loss moduli (E′ and E″)) were calculated at room temperature from the relationship between the calculated applied stress and the response strain obtained by dynamic μ-beam WAXD measurement inside and outside of the spherulites. The E′ values inside and outside of spherulite obtained from the change in spacing of the (110) plane were 1.8 and 1.1 GPa, respectively. Furthermore, the E′ value inside of spherulite obtained from the change in spacing of the (113) plane was 6.0 GPa. These values can be explained by the deformation of crystallite, which depends on the direction of crystal planes. The results obtained here revealed that synchrotron radiation X-ray diffraction measurement gives not only structural information but also the local mechanical properties of the materials E′..
11. Kiminori Uchida, Kazuki Mita, Yuji Higaki, Ken Kojio, Atsushi Takahara, Lamellar orientation in isotactic polypropylene thin films
a complement study via grazing incidence X-ray diffraction and surface/cross-sectional imaging, Polymer Journal, 10.1038/s41428-018-0138-3, 51, 2, 183-188, 2019.02, The crystalline structures of isotactic polypropylene (iPP) thin films were investigated using grazing incident wide-angle X-ray diffraction (GIWAXD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The out-of-plane (110) reflection split with 99° inclination in the GIWAXD pattern. The film surface was covered with flat-on mother lamellae with orthogonal daughter lamellae. The cross-sectional TEM image and the fast Fourier transform-processed image showed vertically aligned daughter lamellae and cross-hatched lateral mother lamellae. Flat-on lamellae may be preferentially produced at the substrate interface, after which the mother lamellae may yield daughter lamellae from the ac plane to give vertically aligned lamellae. The daughter lamellae yield in-plane lamellae with flat-on alignment from the ac plane, resulting in the global growth of a cross-hatched lamellar structure..
12. Rahmawati Rahmawati, Shuhei Nozaki, Ken Kojio, Atsushi Takahara, Naoki Shinohara, Satoshi Yamasaki, Microphase-separated structure and mechanical properties of cycloaliphatic diisocyanate-based thiourethane elastomers, Polymer Journal, 10.1038/s41428-018-0148-1, 51, 2, 265-273, 2019.02, Abstract: Polythiourethane (PTU) and polyurethane (PU) elastomers were prepared from poly(oxytetramethylene) glycol, 1,4-bis(isocyanatomethyl) cyclohexane and a dithiol or diol chain extender with two methylene numbers (tetramethylene (C4) and pentamethylene (C5)). The effect of dithiol and diol and the methylene length of the chain extenders on the microphase-separated structure and mechanical properties of PTU and PU were evaluated. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction measurements revealed that the degree of ordering of hard segment chains in PTUs is lower than that for PU elastomers. However, it was revealed from the DSC, small-angle X-ray scattering and temperature dependent dynamic viscoelasticity measurements that the degree of microphase separation in the PTUs became stronger than that for the PUs. As a result, the mechanical property of PTUs is comparable with PUs. Furthermore, the glass transition temperature for the soft segment of PTU became lower than that for PU. PTU and PU exhibited a larger degree of microphase separation and mechanical property when the chain extender was composed of a tetramethylene (C4) chain compared to a pentamethylene (C5) chain..
13. Ken Kojio, Yudai Kiyoshima, Tomoko Kajiwara, Yuji Higaki, Hung Jue Sue, Atsushi Takahara, Effect of Blend Composition on Scratch Behavior of Polystyrene/Poly(2,6-dimethyl-1,4-phenyleneoxide) Blends, Macromolecular Chemistry and Physics, 10.1002/macp.201800371, 220, 1, 2019.01, The relationship between the scratch behavior and molecular aggregation states of polystyrene (PS), poly(2,6-dimethyl-1,4-phenyleneoxide) (PPO), and their blends, is investigated based on differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), polarized optical microscopy (POM), and indentation and scratch tests. DSC reveals that all the PS/PPO blends show the single glass transition temperature (Tg) and the Tg monotonically increase and Tg breadth exhibits a maximum, with an increase in PPO content. Furthermore, density and intermolecular chain distance obtained by WAXD exhibits maximum and minimum values at near 50 wt% of PPO, respectively. It is evident that densification occurs by blending PS and PPO. The scratch coefficient of friction (SCOF) value of PS is the largest and PS exhibits a fish-scale pattern after scratch testing, while the SCOF value of PPO is much smaller than PS and PPO exhibits smooth groove formation. The PS50/PPO50 and PS20/PPO80 blends exhibit superior scratch and indentation resistance than PS and PPO. Damage morphology observation by POM and indentation tests reveals that molecular orientation is more restricted, and resistance against indentation increases for blends. This is due mainly to densification of the blend system..
14. Yukiro Kitagawa, Kazuhiro Yoshida, Kazuma Takase, Alireza Valanezhad, Ikuya Watanabe, Ken Kojio, Hiroshi Murata, Evaluation of viscoelastic properties, hardness, and glass transition temperature of soft denture liners and tissue conditioner, Odontology, 10.1007/s10266-019-00477-9, 108, 3, 366-375, 2019.01, Soft denture liners and tissue conditioners are widely used for the denture patients to cushion masticatory force and condition abused tissues, respectively. This study assessed methods for the evaluation of the viscoelasticity and glass transition temperature (Tg) of the silicone permanent soft liner, acrylic permanent soft liner, and tissue conditioner. Three rheological parameters of storage modulus (E′), loss modulus (E′′), and loss tangent (tan δ), Tg, and hardness were determined using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and the Shore A0 hardness test. Five specimens were measured for each material. The time–temperature superposition principle was applied to produce master curves of E′, E′′, and tan δ for the tested materials at a reference temperature of 37 °C. The acrylic permanent soft liner and tissue conditioner exhibited viscoelastic behavior and sensitivity to frequency, especially at lower frequencies. The silicone permanent soft liner showed elastic behavior and was frequency-independent. Tg for the acrylic permanent soft liner was higher than that for the tissue conditioner, which in turn was higher than that for the silicone permanent soft liner for both DMA and DSC. In DMA, a higher frequency led to higher Tg values. A positive linear relationship was found between Shore A0 hardness and E′ values, but not E′′ and tan δ values. Shore hardness reflects elasticity, but not viscosity. The results of the present study can be used to improve methods for evaluating the viscoelasticity and Tg of soft denture liners and tissue conditioners..
15. Ken Kojio, Chigusa Nagano, Aya Fujimoto, Shuhei Nozaki, Kazutoshi Yokomachi, Kazutaka Kamitani, Hirohmi Watanabe, Atsushi Takahara, In situ synchrotron radiation X-ray diffraction studies on molecular aggregation structure of nylon 12 films during bulge testing, Soft Matter, 10.1039/c7sm01842h, 14, 9, 1659-1664, 2018.01, It is desirable to establish a method for evaluating mechanical properties, such as modulus and strength, of micrometer and sub-micrometer thick polymer films. Bulge tests, where bulge deformation is imposed on films by the pressure of an inert gas, are suitable for satisfying this demand. However, very few studies on polymer films exist in the literature. In this study, bulge testing equipment for in situ synchrotron radiation wide-angle X-ray diffraction (WAXD) measurements is designed and used to study the relationship between the molecular aggregation structure and the mechanical properties of a crystalline nylon 12 (Ny12) film during bulge testing. Isothermally crystallized and quenched Ny12 films exhibited stress-strain curves similar to those obtained by conventional uniaxial elongation. In situ WAXD measurements during bulge testing revealed that the lattice extension of the crystallites is clearly dependent on crystallinity. Concretely, crystallites in the isothermally crystallized film show higher elastic properties than those in the quenched one. The results of the molecular aggregation structure, including the crystal structure and the amorphous chain surrounding the crystallites, of the films during bulge deformation firstly obtained in this study must be useful for designing toughened polymer films..
16. Yucheng Zhang, Tomoyasu Hirai, Wei Ma, Yuji Higaki, Ken Kojio, Atsushi Takahara, Synthesis of a bio-inspired catechol/phosphorylcholine surface modifier and characterization of its surface properties, Journal of Polymer Science, Part A: Polymer Chemistry, 10.1002/pola.28858, 56, 1, 38-49, 2018.01, Biocompatible and blood-compatible surface modification is urgently needed for stainless steel (SUS)-based human implant devices to avoid inflammation and biofouling. To this end, the use of polymeric surface modifiers, whose surface properties are specifically tailored, is a promising approach since this approach minimizes the impact on device's mechanical properties. However, adhesion between the device and surface modifier is relatively weak, since van der Waals forces are employed, leading to low device durability. To address this issue, this work functionalized poly(ɛ-caprolactone)-b-[poly(α-chloride-ɛ-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine)]2 (PCL-b-(PCL-Cl-b-PMPC)2) with catechol groups via a nucleophilic substitution, whereby the catechol functionalization was optimized. The resultant surface modifier showed strong adhesion toward SUS surfaces, forming a smooth and uniform hydrophilic polymeric film that reduced SUS fouling (i.e., protein). Notably, no significant changes of adhesion between the SUS and thin films (thin film) were observed after immersion for 45 days in a pH 7.4 phosphate buffer solution..
17. Shuhei Nozaki, Tomoyasu Hirai, Yuji Higaki, Kohji Yoshinaga, Ken Kojio, Atsushi Takahara, Effect of chain architecture of polyol with secondary hydroxyl group on aggregation structure and mechanical properties of polyurethane elastomer, Polymer, 10.1016/j.polymer.2017.03.031, 116, 423-428, 2017.05, Polyurethane elastomers (PUEs) based on poly(2-ethyl-1,3-hexamethylene adipate) glycol (PEHA), poly(2,4-diethyl-1,5-pentamethylene adipate) glycol (PDEPA) and poly(2-butyl-2-ethyl-1,3-trimethylene adipate) glycol (PBETA) were synthesized with 4,4’-diphenylmethane diisocyanate (MDI) and 1,4-butane diol (BD)/1,1,1-trimethylol propane (TMP). PEHA has one primary and one secondary hydroxyl groups, but PDEPA or PBETA has two primary hydroxyl groups. The effect of low reactive secondary OH group on molecular aggregation structure and mechanical properties of the PUEs was investigated using Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), dynamic viscoelastic measurement and tensile testing. The study demonstrates that PEHA-based PUE has lower cross-linking density and lower degree of microphase separation than PDEPA- and PBETA-based PUEs. As a result, PEHA-based PUE has lower dynamic storage modulus value at the rubbery plateau region and Young's modulus..
18. Shuhei Nozaki, Shiori Masuda, Kazutaka Kamitani, Ken Kojio, Atsushi Takahara, Goro Kuwamura, Daisuke Hasegawa, Krzysztof Moorthi, Kazuki Mita, Satoshi Yamasaki, Superior Properties of Polyurethane Elastomers Synthesized with Aliphatic Diisocyanate Bearing a Symmetric Structure, Macromolecules, 10.1021/acs.macromol.6b02044, 50, 3, 1008-1015, 2017.02, Polyurethane elastomers (PUEs) containing trans-1,4-bis(isocyanatomethyl)cyclohexane (1,4-H6XDI) have been synthesized by polymerizing 1,4-H6XDI with poly(oxytetramethylene) glycol and 1,4-butanediol. The molecular aggregation state and mechanical properties of these PUEs have been compared with those exhibited by PUE analogues made of MDI and diols. The hard segment chains in the 1,4-H6XDI-based PUEs are found to readily crystallize and form strong hydrogen bonds due to a high symmetry of 1,4-H6XDI molecule. Consequently, the 1,4-H6XDI-based PUEs exhibit well-organized hard segment domains. This leads to their generally superior mechanical properties as compared to those of the well-known MDI-based PUEs. 1,4-H6XDI’s lack of aromatic moieties is expected to greatly enhance color stability of resulting PUEs. All the above features suggest 1,4-H6XDI could replace MDI in a range of applications..
19. Satoshi Yamasaki, Hirokazu Morita, Goro Kuwamura, Daisuke Hasegawa, Ken Kojio, Development of novel polyurethanes with high elasticity and durability based on a cycloaliphatic diisocyanate controlled the stereoisomer structure, Nihon Reoroji Gakkaishi, 10.1678/rheology.45.205, 45, 5, 205-207, 2017.01, We have developed and commercialized novel polyurethane (PU) with high elasticity and durability based on a cycloaliphatic diisocyanate controlled the stereoisomer structure. The diisocyanate is called FORTIMO™ trans-1,4-bis (isocyanatomethyl) cyclohexane (1,4-H6XDI). FORTIMO™ 1,4-H6XDI controlled with high trans isomer structure forms a well-organized hard segment phase. Therefore a micro-phase separation structure between soft segment and hard segment phases is progressed, resulting in an improved elasticity and heat resistance of PU elastomer. In addition, the light stability for long term of this PU is excellent due to an aliphatic structure. FORTIMO™ 1,4-H6XDI based PU achieve superior elasticity and durability which was not able to be realized with the existing diisocyanate. FORTIMO™ 1,4-H6XDI is applicable to various PUs, for example, not only thermoplastic, thermoset PU elastomers, but also water dispersed PU, micro-cellar and flexible PU foam with these advantages. This paper will describe the concept and examples of application of FORTIMO™ PU to industry..
20. Satoshi Yamasaki, Goro Kuwamura, Hirokazu Morita, Daisuke Hasegawa, Ken Kojio, Atsushi Takahara, High performance polyurethane elastomers using new cyclaliphatic diisocyanate, Nihon Reoroji Gakkaishi, 10.1678/rheology.45.261, 45, 5, 261-268, 2017.01, Trans-1,4-bis (isocyanatomethyl) cyclohexane (1,4-H6XDI) has been newly developed as a novel cycloaliphatic diisocyanate with a high symmetric chemical structure. The PUEs were prepared with 1,4-H6XDI, polyesterpolyol as a long chain polyol and 1,4-butanediol (BD) as a chain extender. As the representative aromatic and aliphatic diisocyanates, 4,4'-diphenylmethane diisocyanate (MDI) and dicyclohexyl methane-4,4'-diisocyanate (H12MDI) were also used as the control. As a result, it was revealed that 1,4-H6XDI-based PUEs achieved high elasticity such as higher impact resilience, lower compression set, improved heat resistant, and good light stability which was not able to be realized with the existing diisocyanates. The reason is explained that the hard segment chains of the 1,4-H6XDI-based PUEs crystallized well with formation of hydrogen bonds in the PUEs due to the symmetric structure of 1,4-H6XDI. Thus, the 1,4-H6XDI-based PUEs can provide superior properties such as mechanical and thermal properties and excellent light stability compared to existing diisocyanate-based PUEs by rheological evaluation..
21. Ken Kojio, Structure analysis of elastomer materials using synchrotron radiation x-ray diffraction and scattering measurements, Sen'i Gakkaishi, 73, 5, 197, 2017.
22. Shiki Nojima, Yuji Higaki, Katsuhiro Kaetsu, Ryohei Ishige, Noboru Ohta, Hiroyasu Masunaga, Tomoyasu Hirai, Ken Kojio, Atsushi Takahara, Effect of molecular mobility of pre-ordered phase on crystallization in microphase-separated lamellar morphology of strongly segregated crystalline-crystalline diblock copolymers, Polymer, 10.1016/j.polymer.2017.02.086, 2016.12, The effect of molecular mobility of a pre-crystallized phase on the isothermal crystallization in the microphase-separated lamellar morphology of a strongly segregated crystalline-crystalline block copolymer, poly(ethylene glycol)-block-poly(perfluorooctylethyl acrylate) (PEG-b-PFA-C8), was investigated. The diblock copolymer produced a microphase-separated lamellar morphology in the melt state, and the precedent crystallization of PFA-C8 blocks provided the lamellar confinement field. The counter PEG block crystallized within the lamellar confinement field. The molecular mobility of the pre-crystallized PFA-C8 phase was modulated by the thermal history. The structural evolution was monitored by a complementary combination of in situ time-resolved simultaneous small-angle X-ray scattering/wide-angle X-ray diffraction measurements and thermal analyses. The degree of crystallinity and the melting temperature of the PEG crystals were associated with the molecular mobility of the pre-crystallized PFA-C8 phase. The highly packed PFA-C8 phase (higher-ordered phase) constrained the PEG crystallization, whereas the loosely packed PFA-C8 phase (lower-ordered phase) caused a weak restriction in the PEG crystallization to give relatively ordered PEG crystals. Subsequent crystallization in a confinement field of crystalline-crystalline block copolymers was controlled by adjusting the molecular mobility of the pre-crystallized phase..
23. Shiki Nojima, Yuji Higaki, Ryohei Ishige, Hirofumi Kabayama, Noboru Ohta, Hiroyasu Masunaga, Tomoyasu Hirai, Ken Kojio, Atsushi Takahara, Crystallization-induced structure fluctuation of crystallized microdomain structure composed of strongly segregated crystalline-crystalline diblock copolymers, Polymer, 10.1016/j.polymer.2016.09.024, 102, 256-265, 2016.10, Crystallization-induced structure fluctuations in the layer thickness direction and disordering of pre-crystallized structure in crystallized microdomain structure that consist of a strongly segregated crystalline-crystalline diblock copolymer, poly(ethylene glycol)-block-poly(perfluorooctyl ethyl acrylate) (PEG-b-PFA-C8), were investigated. The structure formation process during isothermal crystallization was monitored by in-situ time-resolved simultaneous SAXS/WAXD measurements and thermal analysis. At early stage of isothermal crystallization, three dimensional growth of the PEG lamellar crystals within lamellar microphase-separated morphology induced the volume shrinkage of PEG phase, resulting in the reduction of PEG layer thickness, increase of PFA-C8 layer thickness and disordering of pre-crystallized PFA-C8 crystals. At late stage of isothermal crystallization, one dimensional growth, thickening of PEG lamellar crystals induced the increase of PEG layer thickness and reduction of PFA-C8 layer thickness. The structure fluctuation in the crystallized microdomain structure depends on the crystal growth dimension..
24. Yoshio Furusho, Takeshi Endo, Keiko Higaki, Katsuhiro Kaetsu, Yuji Higaki, Ken Kojio, Atsushi Takahara, Supramolecular network polymers formed from polyamidine and carboxy-terminated telechelic poly(n-butyl acrylate) via amidinium-carboxylate salt bridges, Journal of Polymer Science, Part A: Polymer Chemistry, 10.1002/pola.28082, 54, 14, 2148-2155, 2016.07, We have prepared the amidinium-carboxylate salt bridge-based supramolecular network polymers from a carboxy-terminated telechelic poly(n-butyl acrylate) and a linear polyamidine having N,N′-di-substituted acetamidine group in the main chain. FTIR measurements indicated that the salt bridge was attributed to the three-dimensional network formation. Virtually, no fluidity was observed for the blend containing equimolar amounts of the carboxyl group and the amidine group, which showed a high G′ value of about 1 MPa at -5 °C. For comparison, the supramolecular network polymers crosslinked by ammonium-carboxylate salt were prepared using a linear polyethyleneimine instead of the polyamidine. The blend with equimolar amounts of the carboxyl group and the secondary amino group showed liquid-like fluidity with a G′ value of about 0.01 MPa at -5 °C, which was attributed to the fact that a certain amount of the carboxyl group remained as its free form, as evidenced by FTIR analysis..
25. Ken Kojio, Front-line polymer science
Current polyurethane science C, Kobunshi, 65, 5, 233-237, 2016.05, Polyurethane studies has been still fascinating to us. In this review, current polyurethane science has been addressed focusing on structure-properties relationship of polyurethane with controlled primary strcutre, structure analysis using synchrotron radiation x-ray diffraction and scattering, development of polyurethane withself- healing properties, environment friendly polyurethanes. It is expected that polyurethane would give new brand properties by studies combining analysis based on synchrotron radiation x-ray and simulation..
26. Tomoyasu Hirai, Yuji Higaki, Ken Kojio, Atsushi Takahara, An effect of surface segregation of polyhedral oligomeric silsesquioxanes on surface physical properties of acrylic hard coating materials, Polymer, 84, 81-88, 2016.02.
27. Patcharida Chouwatat, Shiki Nojima, Yuji Higaki, Ken Kojio, Tomoyasu Hirai, Masaya Kotaki, Atsushi Takahara, An effect of surface segregation of polyhedral oligomeric silsesquioxanes on surface physical properties of acrylic hard coating materials, Polymer, 10.1016/j.polymer.2015.12.037, 84, 81-88, 2016.02, An effect of surface segregation of polyhedral oligomeric silsesquioxanes (POSS) on surface physical properties was investigated. Hard coating layer with various MA8POSS loadings was prepared on a bilayer of soft layer and PMMA substrate via a UV curing process. The scratch resistance of the coating layer showed specific properties. When MA8POSS loadings in the coating layers were less than 10 wt %, the coating layers showed a great performance in scratch resistance. While MA8POSS loadings were higher than 10 wt %, the surface performance was deteriorated. This is because the outermost surface of the coating layer was covered by MA8POSS molecules when the MA8POSS loadings were higher than 10 wt %, resulting in uncompleted curing reaction caused by large steric hindrance of MA8POSS..
28. Tomoyasu Hirai, Y. Nagae, K. L. White, K. Kamitani, M. Kido, T. Uchiyama, Maiko Nishibori, Y. Konishi, K. Yokomachi, R. Sugimoto, K. Saigo, T. Ohishi, Yuji Higaki, Ken Kojio, Atsushi Takahara, Solvent free oxidative coupling polymerization of 3-hexylthiophene (3HT) in the presence of FeCl3 particles, RSC Advances, 10.1039/c6ra23178k, 6, 113, 111993-111996, 2016.01, A solvent free oxidative coupling reaction of 3-hexylthiophene (3HT) within a nanocavity is reported. It is found that 3HT can be encapsulated in nanocavities larger than 1 nm, which corresponds to the size of the molecule. In this case, the side reaction at the 4-position in 3HT is regulated..
29. Ken Kojio, Overseas post-doc experience, Sen'i Gakkaishi, 72, 1, P31-P32, 2016.01.
30. Shota Fujii, Makoto Kido, Masanao Sato, Yuji Higaki, Tomoyasu Hirai, Noboru Ohta, Ken Kojio, Atsushi Takahara, pH-Responsive and selective protein adsorption on an amino acid-based zwitterionic polymer surface, Polymer Chemistry, 10.1039/c5py00783f, 6, 39, 7053-7059, 2015.10, The synergistic interactions between the α-amine and the carboxylic acid in an amino acid have recently been studied as bio-based zwitterions. Here, we report a new amphiphilic polymer containing glutamic acid grafted to the end of a dodecyl polymer side chain, which contains the α-amine and the γ-carboxylic acid of the glutamic acid moiety. The polymer self-assembled into a multilayered structure in the thin film, and the glutamic acid moieties in the polymer side chains were exposed to the polymer film/water interface. Annealing the sample enhanced the formation of a well-oriented lamellar structure in the films. Due to the presence of the glutamic acid moieties at the interface, the surface charge was controllable by pH in buffer solutions, resulting in zwitterionic character at neutral pH. It has been widely accepted that zwitterionic surfaces can exhibit non-fouling for proteins. Interestingly enough, the polymer film showed charge-selective protein adsorption since the synergistic interaction between the α-amine and the γ-carboxylic acid was weaker than conventional amino acid-based zwitterionic systems. This is due to the separated state of the functional groups by a three carbon spacer..
31. Tomoyasu Hirai, Yuji Higaki, Ken Kojio, Atsushi Takahara, X-Ray Absorption Fine Structure Study on the Role of Solvent on Polymerization of 3-Hexylthiophene with Solid FeCl3 Particles, Journal of Polymer Science, Part A, Polymer Chemistry, 53, 2075-2078, 2015.09.
32. Ken Kojio, Improvement of the Low-Temperature Property of Aliphatic Polycarbonate Glycols-Based Polyurethane Elastomers , 10.1166/sam.2015.1913 , 7, 5, 934-939, 2015.05.
33. Ken Kojio, Mutsuhisa Furukawa, Machiko Shimada, Makoto Shimada, Takuya Komatsu, Shuhei Nozaki, Suguru Motokucho, Kohji Yoshinaga, Improvement of the low-temperature property of aliphatic polycarbonate glycols-based polyurethane elastomers, Science of Advanced Materials, 10.1166/sam.2015.1913, 7, 5, 934-939, 2015.01, Structure-property relationship of polyurethane elastomers (PUEs) based on aliphatic carbonate glycols (PCglycols) with various molecular weights (HO-[(CH2)mOC(=O)O]n-(CH2)m-OH, m = 3 and 6, Mn = 1000-3000) were investigated to improve their low-temperature property. Differential scanning calorimetry (DSC) measurement revealed that the glass transition temperature (Tg) of the soft segment in the PUEs decreased ca. 10-25 oC and crystallized hard segment exhibited larger heat of fusion with increasing molecular weight of the PC-glycol. This trend clearly implies that the degree of microphase separation of the PUEs became stronger with an increase in molecular weight of the PC-glycol. In the tensile testing, Young's modulus and tensile strength increased with increase in the degree of microphase separation. In other words, an increase in molecular weight of the PC-glycol gives the PUEs bearing lower Tg and superior mechanical properties..
34. Tomoyasu Hirai, Masanao Sato, Makoto Kido, Yusuke Nagae, Katsuhiro Kaetsu, Yudai Kiyoshima, Shota Fujii, Tomoyuki Ohishi, Kevin L. White, Yuji Higaki, Yasutake Teraoka, Maiko Nishibori, Kazutaka Kamitani, Kenji Hanada, Takeharu Sugiyama, Ryuichi Sugimoto, Kazuhiko Saigo, Ken Kojio, Atsushi Takahara, X-ray absorption fine structure study on the role of solvent on polymerization of 3-hexylthiophene with solid FeCl3 particles, Journal of Polymer Science, Part A: Polymer Chemistry, 10.1002/pola.27720, 53, 18, 2075-2078, 2015.01, Poly(3-hexylthiophene) (P3HT) is an important basic material that is widely used in p-type semiconductor devices for organic solar cells and transistors. time. However, the change is dramatically suppressed in comparison with the initial reaction. This supports that there is polymer adsorption on the ferric chloride particles that regulates formation of the radical cation on the 3HT. In short, the adsorbed polymer appears to poison the catalytic behavior. To clarify the effect of solvent on the polymerization, researchers replaced chloroform with hexane and carried out the reaction under similar conditions. The polymerization is initiated when two radical cations react. A pair of protons departs at the extended part of the dimer to form a neutral structure. Another radical cation is then generated at the end of the extended polymer chain due to reduction of Fe(II), propagating the reaction. Through this reaction, a polymer with high molecular weight is formed..
35. Saburo Yamamoto, Tatsuya Kubozono, Ken Kojio, Atsushi Takahara, Development of total internal reflection raman microscope with an apparatus for adhesion test and changes in depolarization ratio of polymer brush by compressive force, Kobunshi Ronbunshu, 10.1295/koron.2015-0043, 72, 11, 673-680, 2015, A new total internal reflection (TIR) Raman microscope that can be used for adhesion testing based on the Johnson-Kendall-Roberts (JKR) theory was developed. The angle and the focus of the laser beam can be accurately controlled by observing the image of the laser spot on a CCD camera in the spectrometer. As a result, strong Raman signals were obtained. It was observed that the depolarization ratio of polymer brushes changes with the compressive force. This equipment is useful for the analysis of the interface and the anisotropic structure of polymer thin films..
36. Keiji Tanaka, Ken Kojio, The 45th summer seminar - For realization of sustainable society by time- and space-domain controls of fibers, Sen'i Gakkaishi, 71, 6, P267, 2015.
37. Kohji Yoshinaga, Atsushi Yonezawa, Suguru Motokucho, Ken Kojio, Synthesis of ZnO nanoparticles using reverse micelles of block copolymer hybridized with ZnO/PMMA, Kobunshi Ronbunshu, 10.1295/koron.71.644, 71, 12, 644-650, 2014.12, Synthesis of zinc oxide nanoparticles in the core of reverse micelles of poly(methyl methacrylate)-block-poly(acrylic acid) (PMMA-b-PAA) in toluene, and succeeding hybridization with poly(methyl methacylate) (PMMA) to fabricate transparent hybrid films was investigated. Inclusion of a ZnO precursor into the cores of the reverse micelles formed in toluene was carried out by addition of diethyl zinc, and heating the resulting solution to 125°C in an autoclave to form ZnO that formed crystals. Fabrication of ZnO/PMMA hybrid films by a casting method using a mixed solution of the reverse micelles and PMMA resulted in low transparency films due to aggregation of ZnO nanoparticles during film forming. Freeze drying of the reverse micelle solution to prepare a ZnO/PMMA hybrid powder and succeeding hybridization with PMMA by hot-pressing at 150°C and 20 MPa gave highly transparent ZnO/PMMA hybrid films, refractive indexes of which were coincident with calculated values. TEM images showed small domains of PMMA and domains containing ZnO nanoparticles..
38. Kohji Yoshinaga, Yin Yang, Teruhisa Ohno, Suguru Motokucho, Ken Kojio, Inclusion of fullerene in polymer chains grafted on silica nanoparticles in an organic solvent , 高分子学会, 10.1038/pj.2014.24 , 46, 9, 623-627, 2014.09.
39. Suguru Motokucho, Mutsuhisa Furukawa, Masahiro Kawashima, Ken Kojio, Kohji Yoshinaga, Physical properties of poly(tetrahydrofuran)-block-poly(2-ethyl-2- oxazoline) triblock copolymer, Polymer Journal, 10.1038/pj.2013.39, 45, 11, 1115-1119, 2013.11, ABA-type triblock copolymers (PEOxz-PTHF-PEOxz) composed of poly(tetrahydrofuran) (PTHF) and poly(2-ethyl-2-oxazoline) (PEOxz) were synthesized by cationic sequential polymerization. Differential scanning calorimetry and wide-angle X-ray diffraction analyses revealed that PEOxz-PTHF-PEOxzs produced a microphase separation structure, which consisted of a partially crystallized amorphous PTHF phase containing PEOxz chains on both ends. Tensile testing showed that PEOxz-PTHF-PEOxz exhibited tough mechanical properties that differed from those of the brittle PTHF homopolymer. Thus, it was suggested that the amorphous PTHF/PEOxz phase played a role in physically cross-linking the moieties via entanglement, resulting in a PEOxz-PTHF-PEOxz material with tough mechanical properties and the ability to be cold-drawn..
40. Takeo Hyodo, Shu Ichi Furuno, Eriko Fujii, Katsuhide Matsuo, Suguru Motokucho, Ken Kojio, Yasuhiro Shimizu, Porous In2O3 powders prepared by ultrasonic-spray pyrolysis as a NO2-sensing material
Utilization of polymethylmethacrylate microspheres synthesized by ultrasonic-assisted emulsion polymerization as a template, Sensors and Actuators, B: Chemical, 10.1016/j.snb.2013.02.090, 187, 495-502, 2013.01, NO2-sensing properties of porous In2O3 (pr-In2O3) powders prepared by ultrasonic-spray pyrolysis employing polymethylmethacrylate (PMMA) microspheres as a template has been investigated in this study. The PMMA microspheres were synthesized in water by ultrasonic-assisted emulsion polymerization employing methyl methacrylate monomer, sodium lauryl sulfate as a surfactant and ammonium persulfate as an initiator. The PMMA microspheres synthesized was quite uniform and the particle size was ca. 60.2 nm (measured by dynamic light scattering). The microstructure of pr-In2O3 powders prepared was largely dependent on the kind of In2O3 sources. The pr-In2O3 which was prepared from In(NO3)3 as an In 2O3 source (pr-In2O3(N)) consisted of submicron-sized spherical particles with welldeveloped spherical mesopores (several tens of nanometers in pore diameter) and each oxide wall among pores was constructed with meso-sized In2O3 particles connected continuously. On the other hand, the pr-In2O3 which was prepared from InCl3 as an In2O3 source (pr-In2 O3(Cl)) was composed of a large number of dispersed meso-sized particles and a few submicron-sized dense spherical particles. In contrast, the morphology of conventional In2O3 powder (c-In 2O3) prepared by ultrasonic-spray pyrolysis of PMMAfree In(NO3)3 aqueous solution as a reference was relatively dense and roughly spherical with a diameter of ca. 100-700 nm. The responses to 1.0 and 10ppm NO2 of pr-In2O3 sensors in air were much larger than those of a c-In2O3(N) sensor in the temperature range of less than 250°C and 300°C, respectively. In addition, the response and recovery speeds of both the pr-In2O 3 sensors were much faster than those of the c-In2O 3(N) sensor, because of the well-developed porous structure of the pr-In2O3 sensors..
41. Kazuya Z. Suzuki, Hideto Yanagihara, Tomohiko Niizeki, Ken Kojio, Eiji Kita, Room temperature magnetoresistance in a polyimide-Co granular film synthesized by vapor deposition polymerization, Applied Physics Letters, 10.1063/1.4768783, 101, 22, 2012.11, Magnetic and magnetotransport properties of pyromellitic dianhydride-4,4′-oxydianiline polyimide-Co granular thin films prepared by vapor deposition polymerization are investigated. The prepared sample is composed of Co particles with diameters of 2-3 nm homogeneously dispersed in a denatured polyimide matrix. The temperature dependence of the resistivity closely follows the T - 1 / 2 law, suggesting that the dominant conduction mechanism is tunneling between metallic granules embedded in the insulating polyimide matrix. The magnetoresistances at 300 and 90 K are 2.6 and 3.0, respectively. The results indicate that polyimide is a promising material for organic spintronics..
42. Kohji Yoshinaga, Suguru Motokucho, Ken Kojio, Akemi Nakai, Effective dispersion of fullerene with methacrylate copolymer in organic solvent and poly(methyl methacrylate), Colloid and Polymer Science, 10.1007/s00396-012-2707-x, 290, 12, 1221-1226, 2012.08, Dispersion of fullerene, C 60, by addition of polymethacrylate dispersant in methyl methacrylate (MMA) and incorporation of C 60 into poly(methyl methacrylate) (PMMA) were investigated. Copolymers synthesized by radical copolymerization of MMA and 2-naphthyl methacrylate (NMA), poly(MMA-co-NMA), effectively dispersed C 60 in MMA to form clusters of 20 nm. In these cases, addition of minimal 110 naphthyl groups per unit C 60 molecule afforded to give clusters with minimum of 20 nm sizes. Furthermore, block copolymers, poly(MMA-b-NMA) with MMA/NMA mole ratio from 12:1 to 20:1, also efficiently dispersed C 60 to give formation of clusters of 20 nm size by addition of minimal 40 naphthyl groups per unit C 60 molecule, which was corresponding to approximate nine layers of naphthyl group in block copolymer adsorbed on the surface of the cluster. Hybrid films of C 60/PMMA, prepared by casting of C 60-dispersed solution containing PMMA, exhibited absorbance at 400 nm linearly increased with C 60 content..
43. Ken Kojio, Mutsuhisa Furukawa, Shun Matsumura, Suguru Motokucho, Takeshi Osajima, Kohji Yoshinaga, The effect of cross-linking density and dangling chains on surface molecular mobility of network polyurethanes, Polymer Chemistry, 10.1039/c2py20149f, 3, 8, 2287-2292, 2012.08, Chemically cross-linked polyurethanes (PUs) were synthesized with two different cross-linking densities and dangling chain concentrations to understand the difference between the molecular mobility of the bulk and free surface based on dynamic viscoelastic properties, lateral force microscopy (LFM) and scanning viscoelasticity microscopy (SVM) measurements. The PUs were synthesized from poly(oxypropylene) triol (PPT; M n = 3000) and tolylene-2,4-diisocyanate (TDI) with a formulation ratio (= [NCO]/[OH]) of 0.85 and 1.20. The former PU has a lightly cross-linked structure with dangling chains, and the latter one has a densely cross-linked structure with allophanate groups and without dangling chains. The α-relaxation process, associated with glass transition of the PPT chains for the bulk and surface, was observed for both PUs in dynamic viscoelastic properties and lateral force microscopy measurements, respectively. The temperature region, at which the α-relaxation process was observed, for the surface was lower and broader in comparison with bulk and the trend was more obvious for the PU with dangling chains. These results can be explained well with the existence of dangling chains and their segregation at the top surface because of lower conformational entropy..
44. Ken Kojio, Keisuke Matsuo, Suguru Motokucho, Kohji Yoshinaga, Yoshiki Shimodaira, Kazuya Kimura, Simultaneous small-angle X-ray scattering/wide-angle X-ray diffraction study of the microdomain structure of polyurethane elastomers during mechanical deformation, Polymer Journal, 10.1038/pj.2011.48, 43, 8, 692-699, 2011.08, Polyurethane elastomers (PUEs) were prepared with poly(oxytetramethylene) glycol (Mn=2000), 4,4′-diphenylmethane diisocyanate, 1,4-butanediol (BD) and 1,1,1-trimethylol propane (TMP) by a prepolymer method. To evaluate the effect of curing temperature and the ratio of curing and crosslinking agents ((BD/TMP)=(10/0 and 8/2)(wt/wt)) on deformation behavior, four different samples were prepared. In the small-angle X-ray scattering (SAXS) profile for the PUEs prepared at 120 °C, a four-point pattern was observed with the preferred tilt being produced by local torques exerted within the strained soft segments from the initial deformation. At near failure strains, strong meridional scattering appeared and the four-point pattern disappeared. In contrast, the PUEs at 80 °C produced meridional scattering through the deformation. As the microdomain structure of the PUEs prepared at 120 and 80 °C initially possessed cylinder- and sphere-like structures, respectively, the cylinder-like structure might have produced the four-point pattern. Obvious changes in interdomain spacing of PUEs at 120 °C during the deformation process were observed in comparison with the spacing at 80 °C. This was due mainly to the formation of a well-developed, networked, cylinder-like microdomain structure. Strain-induced crystallization of the soft-segment chains evaluated by wide-angle X-ray diffraction results was also consistent with the results from SAXS..
45. Ken Kojio, Mutsuhisa Furukawa, Yoshiteru Nonaka, Sadaharu Nakamura, Control of mechanical properties of thermoplastic polyurethane elastomers by restriction of crystallization of soft segment, Materials, 10.3390/ma3125097, 3, 12, 5097-5110, 2010.12, Mechanical properties of thermoplastic polyurethane elastomers based on either polyether or polycarbonate (PC)-glycols, 4,4'-dipheylmethane diisocyanate (1,1'-methylenebis(4-isocyanatobenzene)), 1,4-butanediol, were controlled by restriction of crystallization of polymer glycols. For the polyether glycol based-polyurethane elastomers (PUEs), poly(oxytetramethylene) glycol (PTMG), and PTMG incorporating dimethyl groups (PTG-X) and methyl side groups (PTG-L) were employed as a polymer glycol. For the PC-glycol, the randomly copolymerized PC-glycols with hexamethylene (C6) and tetramethylene (C4) units between carbonate groups with various composition ratios (C4/C6 = 0/100, 50/50, 70/30 and 90/10) were employed. The degree of microphase separation and mechanical properties of both the PUEs were investigated using differential scanning calorimetry, dynamic viscoelastic property measurements and tensile testing. Mechanical properties could be controlled by changing the molar ratio of two different monomer components..
46. Karen E. Sohn, Ken Kojio, Brian C. Berry, Alamgir Karim, Robert C. Coffin, Guillermo C. Bazan, Edward J. Kramer, Michael Sprung, Jin Wang, Surface effects on the thin film morphology of block copolymers with bulk order-order transitions, Macromolecules, 10.1021/ma1001194, 43, 7, 3406-3414, 2010.04, The morphology of poly(styrene-b-ethylene-r-butylene) (SEB) and poly(styrene-b-ethylener-butylene-b-styrene) (SEBS) thin films annealed both above (165 °C) and below (125 °C) the bulk order-order transition temperatures (OOT) (∼140 °C) was characterized with grazing incidence small-angle X-ray scattering (GISAXS), dynamic secondary ion mass spectrometry (d-SIMS), and atomic force microscopy (AFM). The SEBS thin film morphology is always spherical, regardless of film thickness or annealing temperature, leading us to conclude that the OOT for films up to five layers of spheres is depressed by at least 10 °C relative to the bulk. In contrast, the SEB film morphology at both 125 and 165 °C is always cylindrical, except when the film thickness is less than tcyl, a monolayer of cylinders. For SEB film thicknesses, t, less than tcyl at 165 °C either a partial or full monolayer of spheres forms (thickness tsPh) with coexistence of patches of spheres and cylinders when tsph < t < t cyl. Thus, we conclude that the OOT for SEB film thickness between tcyl and 5tcyl is increased by at least 20 °C over that of the bulk. This complex phase behavior can be understood qualitatively by considering two small contributions to the free energy f per block copolymer chain in the films: (1) an increase in/due to packing frustration and (2) a decrease in f due to the entropy of chain ends near the block copolymer film surfaces. The SEBS has no chain ends near the surface, and we propose that the larger packing frustration of SEBS chains in the square Wigner-Seitz cells of the cylinder monolayer, and the surface half-layers in thicker films, leads to the stabilization of the spherical morphology, which has a smaller packing frustration in the monolayer and surface half-layers. The SEB cylinders and sphere monolayers have the same packing frustration as those of the SEBS, but the contribution of the added entropy of chain ends near the surface is larger for the cylinders than for the spheres, more than offsetting the effect of packing frustration and thus stabilizing the cylindrical morphology at temperatures above the OOT..
47. Ken Kojio, Mutsuhisa Furukawa, Suguru Motokucho, Makoto Shimada, Machiko Sakai, Structure-mechanical property relationships for polycarbonate urethane elastomers with novel soft segments, Macromolecules, 10.1021/ma901317t, 42, 21, 8322-8327, 2009.11, A series of eight aliphatic polycarbonate (PC) glycols with various methylene numbers (HO-[(CH2)mOC(=O)O]2) m-OH, m = 3, 4, 5, 6, 7, 8, 9, and 10) were employed as a soft segment for a synthesis of polyurethane elastomers (PUEs). First of all, viscosity, glass transition temperature, melting point, and crystalline structure of these new PC-glycols were investigated. The PC-glycol-based PUEs were synthesized using the PC-glycols, 4,4′-diphenylmethane diisocyanate, and 1,4-butanediol by a one-shot method. Differential scanning calorimetry and small-angle X-ray scattering measurements revealed that the degree of microphase separation of the PC-glycol-based PUEs became first weaker and then stronger with increasing number of methylene groups of PC-glycols. The threshold carbon number for the degree of microphase separation was six. In the tensile testing, Young's modulus of the PUEs decreased and increased with an increase in the methylene number, which can be explained by the degree of microphase separation. Tensile strength and elongation at break of the PC-glycol-based PUEs increased and decreased with increasing the number of methylene groups. These results are associated with the ease of packing of the PC-glycol chains..
48. Atsushi Takahara, Ken Kojio, Shouren Ge, Tisato Kajiyama, Selective Adsorption of Plasma Protein onto Phase-Separated Domain of Immobilized Organosilane Monolayer Surfaces, In “Advanced Biomaterials in Biomedical Engineering and Drug Delivery Systems” (N. Ogata et al. Eds.), 243-245.
49. Atsushi Takahara, Ken Kojio, Shouren Ge, Tisato Kajiyama, Scanning Force Microscopic Study of Surface Structure and Protein Adsorption Behavior of Organosilane Monolayers, Journal of Vacuum Science & Technology, A14, 3, 1747-1754.
50. Tisato Kajiyama, Shouren Ge, Ken Kojio, Atsushi Takahara, Scanning Force Microscopic Study of Surface Structure and Properties of (Alkylsilane/Fluoroalkylsilane) Mixed Monolayers, Supramolecular Science, 3, 1-3, 123-130.
51. Atsushi Takahara, Shouren Ge, Ken Kojio, Tisato Kajiyama, Scanning Force Microscopy of Surface Structure and Surface Mechanical Properties of Organotrichlorosilane Monolayers Prepared by Langmuir Method, ACS Symposium Series, 694, 204-222.
52. Shouren Ge, Ken Kojio, Atsushi Takahara, Tisato Kajiyama, Bovine Serum Albumin Absorption onto Immobilized Organotrichlorosilane Surface: Influence of the Phase Separation on Protein Adsorption Patterns, Journal of Biomaterials Science, Polymer Edition, 9, 2, 131-150.
53. Ken Kojio, Shouren Ge, Atsushi Takahara, Tisato Kajiyama, Molecular Aggregation State of n-Octadecyltrichlorosilane Monolayer Prepared at an Air/Water Interface, Langmuir, 14, 5, 971-974.
54. Atsushi Takahara, Shouren Ge, Ken Kojio, Tisato Kajiyama, In Situ Atomic Force Microscopic Observation of Albumin Adsorption onto Phase-Separated Organosilane Monolayer Surface, Journal of Biomaterials Science, Polymer Edition, 11, 1, 111-120.
55. Ken Kojio, Atsushi Takahara, Tisato Kajiyama, Aggregation Structure and Surface Properties of 18-Nonadecenyltrichlorosilane Monolayer and Multilayer Films Prepared by the Langmuir Method, ACS Symposium Series, 729, 332-352.
56. Ken Kojio, Atsushi Takahara, Kazuhiko Omote, Tisato Kajiyama, Molecular Aggregation State of n-Octadecyltrichlorosilane Monolayers Prepared by the Langmuir and Chemisorption Methods, Langmuir, 16, 8, 3932-3936.
57. Ken Kojio, Atsushi Takahara, Tisato Kajiyama, Formation Mechanism of n-Octadecyltrichlorosilane Monolayer Prepared at the Air/Water Interface, Colloids & Surfaces A, 169, 1-3, 295-306.
58. Ken Kojio, Atsushi Takahara, Tisato Kajiyama, Molecular Aggregation State and Molecular Motion of Organosilane Monolayers Prepared at the Air/Water Interface, Langmuir, 16, 24, 9314-9320.
59. Ken Kojio, Atsushi Takahara, Tisato Kajiyama, Aggregation Structure and Surface Properties of Immobilized Fluoroalkylsilanes and Their Mixed Monolayers, ACS Symposium Series, 787, 31-47.
60. Atsushi Takahara, Yukiko Hara, Ken Kojio, Tisato Kajiyama, Scanning Force Microscopic Study of Protein Adsorption on the Surface of Organosilane Monolayers Prepared by the Langmuir-Blodgett Method, Macromolecular Symposia, 167, 1, 271-284.
61. Tisato Kajiyama, Ryota Tominaga, Ken Kojio, Keiji Tanaka, Structural Study of Crystal Transition from Hexagonal to Rectangular Phase of Lignoceric Acid Monolayers, Bulletin of Chemical Society Japan, 74, 4, 765-771.
62. Ken Kojio, Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Novel Method to Prepare Organosilane Monolayers on Solid Substrate, Bulletin of Chemical Society Japan, 74, 8, 1397-1401.
63. Atsushi Takahara, Yukiko Hara, Ken Kojio, Tisato Kajiyama, Plasma Protein Adsorption Behavior onto the Surface of Phase-separated Organosilane Monolayers on the basis of Scanning Force Microscopy, Colloids & Surfaces B, 23, 2-3, 141-152.
64. Atsushi Takahara, Ken Kojio, Tisato Kajiyama, Effect of Aggregation State on Nanotribological Behaviors of Organosilane Monolayer, Ultramicroscopy, 91, 1-4, 203-213.
65. Ken Kojio, Sangmin Jeon, Steve Granick, Confinement-Induced Differences between Dielectric Normal Modes and Segmental Modes of an Ion-Conducting Polymer, European Physical Journal E, 8, 2, 167-173.
66. Keiji Tanaka, Ken Kojio, Reiko Kimura, Atsushi Takahara, Tisato Kajiyama, Surface Relaxation Processes of Poly(methyl methacrylate) Brushes Prepared by Atom Transfer Radical Polymerization, Polymer Journal, 35, 1, 44-49.
67. Mutsuhisa Furukawa, Yukinori Hamada, Ken Kojio, Aggregation Structure and Mechanical Properties of Functionally Graded Polyurethane Elastomers, Journal of Polymer Science: Polymer Physics, 41, 20, 2355-2363.
68. Yasumitsu Sakamoto, Hisashi Ichikawa, Masanobu Nozaki, Ken Kojio, Mutsuhisa Furukawa, Syntheses and Properties of Myofibril Gels of Fish, Transaction of Materials Research Society of Japan, 28, 3, 937-940.
69. Michael Y. Gelfer, Christian Burger, Alexander Y. Fadeev, Igors Sics, Benjamin Chu, Benjamin S. Hsiao, Amy Heintz, Ken Kojio, Shaw Ling Hsu, Mayu Si, Miriam Rafailovich, Thermally Induced Phase Transitions and Morphological Changes in Organoclays, Langmuir, 20, 9, 3746-3758.
70. Ken Kojio, Tomoya Fukumaru, Mutsuhisa Furukawa, Highly Softened Polyurethane Elastomer Synthesized with Novel 1,2-Bis(isocyanate) ethoxyethane, Macromolecules, 37, 9, 3287-3291.
71. Ken Kojio, Sadaharu Nakamura, Mutsuhisa Furukawa, Effect of Side Methyl Groups of Polymer Glycol on Elongation-induced Crystallization Behavior of Polyurethane Elastomers, Polymer, 45, 24, 8147-8152.
72. Ken Kojio, Yoshiteru Nonaka, Mutsuhisa Furukawa, Effect of Composition Ratio of Copolymerized Polycarbonate Glycol on Microphase Separated Structure and Mechanical Properties of Polyurethane Elastomers, Journal of Polymer Science: Polymer Physics, 42, 24, 4448-4458.
73. Masafumi Horiuchi, Ken Kojio, Mutsuhisa Furukawa, Surface Structure and Properties of (Oligourethane with Fluoroalkyl End Groups /Polyurethane) Blend Thin Films, Transactions of the Materials Research Society of Japan, 30, 3, 635-638.
74. Mutsuhisa Furukawa, Yoshitaka Mitsui, Tomoya Fukumaru, Ken Kojio, Microphase-separated Structure and Mechanical Properties of Novel Polyurethane Elastomers Prepared with Ether Based Diisocyanate, Polymer, 46, 24, 10817-10822.
75. Mutsuhisa Furukawa, Ken Kojio, Yoshie Minamida, Yasumitsu Sakamoto, Properties of Fish Protein–Hydrophilic Polymer Hybrid Gels, Polymer Bulletin, 58, 1, 75-82.
76. Tetsuo Masubuchi, Machiko Sakai, Ken Kojio, Mutsuhisa Furukawa, Takeshi Aoyagi, Structure and Properties of Aliphatic Poly(carbonate) Glycols with Different Methylene Unit Length, e-Journal of Soft Materials, 3, 55-63.
77. Ken Kojio, Shohei Nakashima, Mutsuhisa Furukawa, Microphase-separated Structure and Mechanical Properties of Norbornane Diisocyanate-based Polyurethanes, Polymer, 48, 4, 997-1004.
78. Ken Kojio, Yusuke Uchiba, Yoshitaka Mitsui, Mutsuhisa Furukawa, Sono Sasaki, Hiroyasu Matsunaga, Hiroshi Okuda, Depression of Microphase-Separated Domain Size of Polyurethanes in Confined Geometry, Macromolecules, 40, 8, 2625-2628.
79. Satoshi Yamasaki, Daisuke Nishiguchi, Ken Kojio, Mutsuhisa Furukawa, Effects of Polymerization Method on Structure and Properties of Thermoplastic Polyurethanes, Journal of Polymer Science: Polymer Physics, 45, 7, 800-814.
80. Satoshi Yamasaki, Daisuke Nishiguchi, Ken Kojio, Mutsuhisa Furukawa, Effects of Aggregation Structure on Rheological Properties of Thermoplastic Polyurethanes, Polymer, 48, 16, 4793-4803.
81. Mutsuhisa Furukawa, Ken Kojio, So Kugumiya, Yusuke Uchiba, Yoshitaka Mitsui, Microphase Separation of Bulk and Ultrathin Films of Polyurethane Elastomers, Macromolecular Symposia, 267, 1, 9-15.
82. Ken Kojio, Sadaharu Nakamura, Mutsuhisa Furukawa, Effect of Side Group of Polymer Glycol on Microphase-separated Structure and Mechanical Properties of Polyurethane Elastomers, Journal of Polymer Science: Polymer Physics, 46, 19, 2054-2063.
83. Teerin Kongpun, Suguru Motokucho, Ken Kojio, Mutsuhisa Furukawa, Effect of Ratio of Diol to Triol as Curing Agents on the Microaggregation Structure and Adhesion Properties of Segmented Polyurethanes, 日本接着学会誌, 44, 9, 333-340.
84. Teerin Kongpun, Ken Kojio, Mutsuhisa Furukawa, The Influence of Curing Temperature on Micro-aggregation Structure and Adhesion Properties of Segmented Polyurethanes, 日本接着学会誌, 44, 12, 458-464.
85. Ken Kojio, Yusuke Uchiba, So Kugumiya, Yuichi Nishino, Mutsuhisa Furukawa, The Microphase- separated Structure of Polyurethane Bulk and Thin Films, Polymer Journal, 41, 2, 118-124.
86. Teerin Kongpun, Ken Kojio, Mutsuhisa Furukawa, Effect of Polymer Glycols on Micro-aggregation Structure and Mechanical Properties of Spherulite Size Graded Polyurethane Elastomers, Journal of Applied Polymer Science, 113, 3, 1154-1161.
87. Ken Kojio, Yoshitaka Mitsui, Mutsuhisa Furukawa, Synthesis and Properties of Highly Hydrophilic Polyurethane Based on Diisocyanate with Ether Group, Polymer, 50, 15, 3693-3697.
88. Baiju John, Ken Kojio, Mutsuhisa Furukawa, High Performance Polyamide 6 Fibers Using Polycarbonate Based Thermoplastic Polyurethane Thin Film Coatings- a Novel Method, Polymer Journal, 41, 5, 319-326.
89. Baiju John, Suguru Motokucho, Ken Kojio, Mutsuhisa Furukawa, Polyamide 6 Fibers with Superior Mechanical Properties: Thermoplastic Polyurethane Coating Techniques, SEN’I GAKKAISHI, Vol.65, 65, 9, 236-240.
90. Ken Kojio, Yusuke Uchiba, Yasunori Yamamoto, Suguru Motokucho, Mutsuhisa Furukawa, Chain and Mirophase-separated Structures of Ultrathin Polyurethane Films, Journal of Physics, Conference Series, 184, 012028.
91. Ken Kojio, Mutsuhisa Furukawa, Suguru Motokucho, Makoto Shimada, Machiko Sakai, Structure-Mechanical Property Relationship for Poly(carbonate urethane) Elastomers with Novel Soft Segments, Macromolecules, 42, 21, 8322-8327.
92. Karen E. Sohn, Ken Kojio, Brian C.Berry, Alamgir Karim, Robert C. Coffin, Guillermo C. Bazan, Edward J. Kramer, Michael Sprung, Jim Wang, Surface Effects on the Thin Film Morphology of Block Copolymers with Bulk Order-Order Transition, Macromolecules, 43, 7, 3406-3414.
93. Ken Kojio, Mutsuhisa Furukawa, Yoshiteru Nonaka, Sadaharu Nakamura, Control of Mechanical Properties of Thermoplastic Polyurethane Elastomers by Restriction of Crystallization of Soft Segment, Materials, 3, 12, 5097-5110.
94. Takeo Hyodo, Shuichi Furuno, Suguru Motokucho, Ken Kojio, Yasuhiro Shimizu, Preparation of porous indium oxide sensor materials by utilizing polymer microspheres as a template, Chemical Sensors, 27, 10-12.
95. Ken Kojio, Keisuke Matsuo, Suguru Motokucho, Kohji Yoshinaga, Yoshiki Shimodaira and Kazuya Kimura, Simultaneous small-angle X-ray scattering/wide-angle X-ray diffraction study of the microdomain structure of polyurethane elastomers during mechanical deformation, Polymer Journal, 43, 8, 692-699.
96. Kohji Yoshinaga, Suguru Motokucho, Ken Kojio, Akemi Nakai, Effective dispersion of fullerene with methacrylate copolymer in organic solvent and poly(methyl methacrylate), Colloid and Polymer Science, 290, 12, 1221-1226.
97. Ken Kojio, Mutsuhisa Furukawa, Shun Matsumura, Suguru Motokucho, Takechi Osajima, Kohji Yoshinaga, The effect of crosslink density and dangling chains on surface molecular mobility of network polyurethanes, Polymer Chemistry, 3, 8, 2287-2292.
98. Kazuya Z. Suzuki, Hideto Yanagihara, Tomohiko Niizeki, Ken Kojio, and Eiji Kita, Room temperature magnetoresistance in a polyimide-Co granular film synthesized by vapor deposition polymerization, Applied Physics Letters, 101, 222401, 1-4.
99. Takeo Hyodo, Shuichi Furuno, Emiko Fujii, Katsuhide Matsuo, Suguru Motokucho, Ken Kojio, Yasuhiro Shimizu, Porous In2O3 powders prepared by ultrasonic-spray pyrolysis as a NO2-sensing material: Utilization of polymethylmethacrylate microspheres synthesized by ultrasonic-assisted emulsion polymerization as a template, Sensors and Actuators, B: Chemical, 187, 495-502.