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

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


Reports
1. Tisato Kajiyama, Shouren Ge, Ken Kojio, Atsushi Takahara, Scanning force microscopic study of surface structure and properties of (alkylsilane/fluoroalkylsilane) mixed monolayers, Supramolecular Science, 10.1016/0968-5677(96)00024-7, 1996.01, (Alkylsilane/fluoroalkylsilane) mixed monolayers were immobilized covalently on a silicon wafer surface with stable surface structure. Atomic force microscopic observation of the n-octadecyltrichlorosilane(OTS)/[2-(perfluorooctyl)ethyl]trichlorosila ne (FOETS) mixed monolayer revealed that the crystalline OTS circular domains of ca. 1-2 μm in diameter were surrounded by a sea-like amorphous FOETS matrix, even though the molar fraction of OTS was above 75%. Also, the phase-separated monolayer can be prepared from FOETS, and a non-polymerizable and crystallizable amphiphile such as lignoceric acid (LA). The phase separation of the (alkylsilane/fluoroalkylsilane) mixed monolayer might be attributed to both faster spreading of FOETS molecules on the water surface and the crystallizable characteristics of alkylsilane molecules. The mixed monolayer of crystalline alkylsilane (OTS) and amorphous alkylsilane (n-dodecyltrichlorosilane, DDTS) formed a phase-separated structure on the water surface because of the crystallizable characteristics of OTS. Lateral force microscopic (LFM) observation revealed that the order of the magnitude of lateral force generated against the silicon nitride tip was: n-triacontyltrichlorosilane (TATS) domain with longer alkyl chain>amorphous FOETS matrix>crystalline OTS domain. On the other hand, scanning viscoelasticity microscopic observation revealed that the order of the magnitude of modulus was: Si substrate>crystalline OTS domain>amorphous FOETS matrix..
2. Shouren Ge, Ken Kojio, Atsushi Takahara, Tisato Kajiyama, Bovine serum albumin adsorption onto immobilized organotrichlorosilane surface
Influence of the phase separation on protein adsorption patterns
, Journal of Biomaterials Science, Polymer Edition, 10.1163/156856298X00479, 1998.01, Octadecyltrichlorosilane (OTS) and [2-(perfluorooctyl)ethyl]trichlorosilane (FOETS) monolayers and their mixed monolayer were polymerized on a water subphase and subsequently immobilized onto a silicon wafer surface by covalent bonding. Atomic force microscopic (AFM) observation of the mixed (OTS/FOETS) monolayer revealed the formation of a phase-separated structure. Protein-adsorption behavior onto the monolayers was investigated in situ on the basis of an attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopic flow cell method and the morphology of the monolayer surface-adsorbed bovine serum albumin (BSA) was observed by AFM. Protein adsorption behavior observed by ATR-FT-IR flow cell method revealed that the amount of BSA adsorption onto the OTS and FOETS monolayers increased remarkably at an initial experimental stage and attained a steady state within a few minutes at pH 7.5. The amount of steady state adsorption was c. 0.18-0.2 μgcm-2. AFM observation of the monolayer after exposure to BSA solution suggested that BSA adsorbed in the end-on adsorption state on OTS monolayer and side-on one in the FOETS monolayer, respectively. However, in the case of the mixed (OTS/FOETS) monolayer, ATR-FT-IR flow cell experiment revealed that the amount of steady state adsorption of BSA was suppressed. Also, AFM observation revealed that at pH 7.5, BSA preferentially adsorbed onto the FOETS phase of the mixed (OTS/FOETS) monolayer, which had a higher interfacial free energy against water. On the other hand, BSA adsorbed homogeneously onto the OTS and FOETS phases at the isoelectric point of BSA (pH 4.7). These results indicate that the preferential adsorption of BSA onto the FOETS phase in the mixed (OTS/FOETS) monolayer system is due to: (1) the minimization of the interfacial free energy between a monolayer surface and an aqueous solution; and (2) the electrostatic repulsion between BSA molecules bearing negative charges..
3. Ken Kojio, Shouren Ge, Atsushi Takahara, Tisato Kajiyama, Interaction between Polymeric Organosilane Monolayer and Plasma Protein, KOBUNSHI RONBUNSHU, 10.1295/koron.55.344, 1998.01, The n-octadecyltrichlorosilane (OTS) and the [2-(perfluorooctyl)ethyl]trichlorosilane (FOETS) monolayers, and their mixed monolayer were used as the model systems for the study of protein adsorption behavior because of their remarkable surface stability. The attenuated total reflection infrared (ATR-FT-IR) flow cell studies revealed that the adsorption amount of bovine serum albumin (BSA) onto each OTS and FOETS monolayer steeply increased in an initial stage of adsorption experiment and attained an equilibrium within a few minutes at pH 7.5. In the case of the (OTS/ FOETS) (50/50 mol/mol) mixed monolayer, the amount of protein adsorption was suppressed. AFM observation in a BSA solution at pH 7.5 revealed that BSA was preferentially adsorbed onto the FOETS phase of the (OTS/FOETS) mixed monolayer, while selective adsorption of BSA onto the FOETS phase was not observed at the isoelectric point of BSA (pH 4.7). Furthermore, [(3-mercaptopropyl)trimethoxysilane (MTS)/FOETS] mixed monolayer with reactive -SH group in domain was prepared. Then, the BSA was selectively immobilized onto the MTS phase..
4. Atsushi Takahara, Ken Kojio, Tisato Kajiyama, Aggregation structure and surface properties of immobilized polyalkylsiloxane ultrathin films prepared at the air/water interface, American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 1998.03.
5. Ken Kojio, Shouren Ge, Atsushi Takahara, Tisato Kajiyama, Molecular aggregation state of n-octadecyltrichlorosilane monolayer prepared at an air/water interface, Langmuir, 10.1021/la970040p, 1998.03, Molecular arrangement of polymerized n-octadecyltrichlorosilane (OTS, CH3(CH2)17SiCl3) monolayer transferred onto hydrophilic substrate by an upward drawing method was investigated with a transmission electron microscope (TEM) and an atomic force microscope (AFM). The electron diffraction (ED) pattern of the OTS monolayer revealed that the OTS molecules were regularly arranged in a hexagonal array with a (10) spacing of ca. 0.42 nm. The high-resolution AFM image of the OTS monolayer in a scan area of 10 × 10 nm2 exhibited the individual methyl group of which packing was a hexagonal array in a similar molecular arrangement concluded on the basis of the ED study. Also, the point defect in the crystalline OTS monolayer was successfully observed for the first time..
6. 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, 1998.12, Organochlorosilane monolayers were polymerized on the water surface and immobilized onto the silicon wafer surface by Langmuir method. The electron diffraction (ED) pattern of the n-octadecyltrichlorosilane(OTS) monolayer revealed that OTS molecules were regularly arranged in a hexagonal array with the (10) spacing of ca. 0.42 nm. On the other hand, ED study revealed that the [2-(perfluorooctyl)ethyl]trichlorosilane (FOETS) monolayer was amorphous state at room temperature. The high-resolution atomic force microscopic (AFM) image of the OTS monolayer in a scan area of 10×10 nm2 exhibited the individual methyl groups of which packing was a hexagonal array in a similar molecular arrangement concluded by the ED study. AFM observation of the (OTS/FOETS) mixed monolayer revealed that the crystalline OTS circular domains of ca. 1-2 μm in diameter were surrounded by a sea-like amorphous FOETS matrix, even though the molar fraction of OTS was above 75%. Phase separation was observed for monolayer prepared from FOETS and non-polymerizable and crystallizable amphiphile such as lignoceric acid (LA). The phase separation of the (alkylsilane/fluoroalkylsilane) mixed monolayer might be attributed to both the crystallizable characteristics of alkylsilane molecules and faster spreading of FOETS molecules on the water surface. The mixed monolayer of crystalline alkylsilane (OTS) and amorphous alkylsilane (n-dodecyltrichlorosilane, DDTS) formed phase-separated structure on the water surface because of the crystallizable characteristics of OTS. Lateral force microscopic (LFM) observation revealed that the order of the magnitude of lateral force generated against the silicon nitride tip was crystalline Si substrate >crystalline n-triacontyltrichlorosilane (TATS) domain> crystalline n-dococyltrichlorosilane (DOTS) domain> amorphous FOETS matrix > crystalline OTS domain>amorphous DDTS matrix. On the other hand, scanning viscoelasticity microscopic observation revealed that the order of the magnitude of modulus was Si substrate > crystalline OTS domain > amorphous FOETS matrix..
7. 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, 1999.12, The 18-nonadecyltrichlorosilane (NTS) monolayer with a vinyl end group was prepared by the Langmuir method. The monolayer with a hydrophilic carboxylated surface was subsequently obtained by oxidation of the vinyl end group. For the multilayer preparation, the NTS monolayer was immobilized onto the hydrophilic carboxylated NTS (NTSCOOH) monolayer. The NTS multilayer film was obtained by repetitions of depositions and oxidations. Aggregation structure of the NTS multilayer film was evaluated on the basis of X-ray reflectivity (XR), Brewster angle infrared (IR) spectroscopic measurements, electron diffraction (ED) and atomic force microscopic (AFM) observations. It was revealed that the NTS multilayer film with a well-ordered structure could be prepared by the Langmuir method. The local height control was performed by utilizing the phase-separated mixed monolayer being composed of the NTS and [2-(perfluorooctyl)ethyl]trichlorosilane (FOETS) molecule. The (NTS/FOETS) mixed monolayer showed phase-separated structure like sea-island, whose domain and matrix phases were composed of crystalline NTS and amorphous FOETS molecules, respectively. The (NTSCooH/FOETS) mixed monolayer with the hydrophilic domain and the hydrophobic matrix was obtained by selective oxidization of the NTS phase in the (NTS/FOETS) mixed monolayer. Furthermore, the local height control on the NTSCOOH phase of the (NTSCOOH/FOETS) mixed monolayer was performed by chemisorption of NTS from the solution. The height increase in the NTSCOOH phase was confirmed by AFM and lateral force microscopy (LFM)..
8. 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, 10.1163/156856200743535, 2000.01, A mixed (n-octadecyltrichlorosilane (OTS)/[2-(perfluorooctyl)ethyl]trichlorosilane (FOETS)) monolayer was prepared on the water subphase and was subsequently immobilized onto the silicon wafer surface by chemical bonds. Atomic force microscopic (AFM) observation of the mixed (OTS/FOETS) monolayer revealed the formation of a phase-separated structure. In situ AFM observation of the adsorption behavior of bovine serum albumin (BSA) onto the mixed (OTS/FOETS) monolayers, successfully showed the adsorption behavior of BSA onto the phase-separated surface. It also revealed that in the case of pH 7.5, BSA was preferentially adsorbed onto the lower surface free energy FOETS phase of the mixed (OTS/FOETS) monolayer. On the other hand, BSA was adsorbed homogeneously onto the OTS and FOETS phases at the isoelectric point of BSA (pI 4.7). These results indicate that the preferential adsorption of BSA onto the FOETS phase in the mixed (OTS/FOETS) monolayer system may be due to: (1) the minimization of interfacial free energy between a monolayer surface and an aqueous solution; and (2) the electrostatic repulsion among BSA molecules bearing negative charges..
9. Ken Kojio, Atsushi Takahara, Kazuhiko Omote, Tisato Kajiyama, Molecular aggregation state of n-octadecyltrichlorosilane monolayers prepared by the Langmuir and chemisorption methods, Langmuir, 10.1021/la9909042, 2000.04, A comparative study in molecular arrangements of the n-octadecyltrichlorosilane (OTS) monolayer prepared by the Langmuir method and the chemisorption methods were carried out on the basis of grazing incidence X-ray diffraction (GIXD) and X-ray reflectivity (XR) measurements. The OTS molecules in the Langmuir OTS monolayer uniformly tilt ca. 8-10° to the surface normal and packed in a hexagonal lattice with the (10) spacing of 0.412 nm. On the other hand, the OTS molecules in the chemisorbed OTS monolayer tilt ca. 15-17° to the surface normal and also crystallite orient randomly in the two-dimensional plane. The average magnitude of the (10) spacing of the chemisorbed OTS monolayer was ca. 0.417 nm. Direct evidence that the packing density of the Langmuir OTS monolayer was higher than that of the chemisorbed OTS monolayer was obtained by GIXD and XR measurements for the first time..
10. Ken Kojio, Atsushi Takahara, Tisato Kajiyama, Formation mechanism of n-octadecyltrichlorosilane monolayer prepared at the air/water interface, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/S0927-7757(00)00444-1, 2000.09, The n-octadecyltrichlorosilane (OTS) monolayer was prepared by the Langmuir-Blodgett method. The formation mechanism of the OTS monolayer on the water subphase was investigated on the basis of electron diffraction (ED) study, Fourier transform infrared external reflection spectroscopic (FT-IR/ERS) measurement and high-resolution atomic force microscopic (AFM) observation. Morphological changes in the monolayer in a compression process were observed by AFM. FT-IR/ERS measurement was performed for the monolayer at the air/water interface, and that the ED and AFM observations were done for the monolayer transferred onto substrate. ED study and high-resolution AFM observation revealed that the OTS monolayer was in a crystalline state at 293 K. Also, FT-IR/ERS measurement and AFM observation showed that the OTS molecules crystallize and polymerize spontaneously right after spreading a toluene solution of OTS on the water subphase. Then, during a monolayer compression, the crystalline OTS monolayer domain did not form the larger ones by sintering at the crystalline domain interface at 293 K. Also, AFM and ED observations revealed that the defect-diminished OTS monolayer could be successfully prepared by using the multi-step creep method..
11. Ken Kojio, Atsushi Takahara, Tisato Kajiyama, Molecular aggregation state and molecular motion of organosilane monolayers prepared at the air/water interface, Langmuir, 10.1021/la0004303, 2000.11, Relationships between the molecular aggregation state and the molecular motion of organosilane monolayers with various chain lengths prepared by the Langmuir-Blodgett (LB) method were investigated by lateral force microscopic, Fourier transform-infrared (FT-IR) spectroscopic, and electron diffraction (ED) measurements. The lateral force of the organosilane monolayers increased with increasing their chain length. This is mainly because the intermolecular cohesive energy is proportional to the number of carbons in a chain. The lateral force of the alkylsilane monolayer was compared with that of the fluoroalkylsilane monolayer for the corresponding alkyl chain length. Consequently, the fluoroalkylsilane monolayer showed higher lateral force than the alkylsilane one. Temperature-dependent ED and FT-IR measurements revealed that the molecular aggregation state of the n-octadecyltrichlorosilane (OTS) monolayer changed from the rectangular lattice to the amorphous state via the hexagonal lattice with increasing temperature. The transition temperatures, rectangular to hexagonal and hexagonal to amorphous, were found to be 240 and 333 K, respectively. The distinct lateral force decrease was concurrently observed for the OTS monolayer at 240 and 333 K. The remarkable decrement of the lateral force at 240 K might be attributed to the decreasing molecular density and the activation of molecular motion (rotational motion along the molecular axis) owing to the rectangular-hexagonal crystal transition. And, the second remarkable depression of the lateral force observed at 333 K might come from the activation of thermal molecular motion due to the melting of alkyl chains..
12. Ken Kojio, Atsushi Takahara, Tisato Kajiyama, Aggregation Structure and Surface Properties of Immobilized Fluoroalkylsilanes and Their Mixed Monolayers, ACS Symposium Series, 2001, Stable fluoroalkyl, alkyl and mixed fluoroalkyl/alkyl monolayers were prepared on solid substrates by the Langmuir method. The n-octadecyltrichlorosilane (OTS), 18-nonadecenylrichlorosilane (NTS) and [3-(perfluorododecyl)propyloxy]triethoxysilane (FDOPTES) in monolayers were in a crystalline state at 293 K, as by electron diffraction (ED) studies. In contrast, the n-dodecyltrichlorosilane (DDTS) and [2-(perfluorooctyl)ethyl] -trichlorosilane (FOETS) monolayers with shorter hydrophobic chains were in an amorphous state at 293 K. Molecular images of the crystalline OTS and FDOPTES monolayers were acquired with high-resolution atomic force microscopy (AFM). The direct observation of the molecular arrangement of the crystalline OTS and FDOPTES was successfully achieved The (10) spacings for these monolayers corresponded well to the cross section area of the alkyl and fluoroalkyl chains. It was revealed from the contact angle measurements that the magnitudes of surface free energies of the fluoroalkylsilane monolayers were higher than of the alkylsilane monolayers. The surface free energy of the crystalline fluoroalkylsilane monolayer (FDOPTES monolayer) was higher than that of the amorphous monolayers due to high orientation of the fluoromethyl end groups at the monolayer surface. AFM observation revealed that the (crystalline OTS/amorphous FOETS) mixed monolayer was in a phase-separated state due to the crystallization of the OTS molecules. The (crystalline NTS/amorphous FOETS) mixed monolayer also showed a phase separation. By oxidation of the NTS phase in the (NTS/FOETS) mixed monolayer, a phase-separated structure with large suface energy gap can be constructed. The surface properties of the mixed monolayer was evaluated based on lateral force microscopy (LFM) and adhesion force measurement. Literatures cited..
13. 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, 10.1002/1521-3900(200103)167:1<271::AID-MASY271>3.0.CO;2-Y, 2001.01, The n-octadecyltrichlorosilane (OTS, CH3(CH2)17SiCl3), 18-nonadecenyltrichlorosilane (NTS, CH2=CH(CH2)17SiCl3), [2-(perfluorooctyl)ethyl] trichlorosilane (FOETS, CF3(CF2)7CH2 CH2SiCl3) monolayers, and their mixed monolayers were used as the model substrates for the study of protein adsorption mechanism. Surface plasmon resonance (SPR) spectroscopy was applied to analyze the protein adsorption behavior onto the surface of the monolayers. Atomic force microscope (AFM) was used to observe the monolayer surfaces after exposure of these monolayers to bovine serum albumin (BSA) and Δ-globulin(IgG) solution. AFM observation revealed that the charged protein either below or above the isoelectric point was preferentially adsorbed onto the FOETS phase of the (OTS/FOETS) mixed monolayer. SPR revealed that the amount of adsorbed protein in the charged state was lower than that in the neutral state. These results indicate that the preferential adsorption of protein onto the FOETS phase for the mixed monolayer systems at either below or above pI is due to (1) the minimization of interfacial free energy between the monolayer surface and the buffer solution, and (2) the electrostatic repulsion among protein molecules bearing charges..
14. T. Kajiyama, R. Tominaga, Ken Kojio, Keiji Tanaka, Structural study of crystal transition from hexagonal to rectangular phase of lignoceric acid monolayers, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.74.765, 2001.04, Crystal transition behavior of lignoceric acid (LA) monolayer was structurally investigated by electron diffraction (ED) in conjunction with scanning force microscopy (SFM). LA molecules form two-dimensional hexagonal crystallites right after one spreads a solution at the air/water interface. The hexagonal-rectangular transition of the LA monolayer was attained by two different experimental procedures: monolayer compression under an isothermal condition and monolayer cooling under an isobaric condition. In the compression process, the hexagonal and rectangular phases coexisted in the monolayer at the surface pressure, π, of 10 mN m-1, which was slightly lower than the plateau pressure, and the subphase temperature of 293 K. When the π exceeded the plateau pressure, the hexagonal phase in the LA monolayer was entirely transformed to the rectangular one. High-resolution SFM showed that the crystal transition from the hexagonal to rectangular phase proceeded via a quasi-disordered phase upon compression. A similar hexagonal-rectangular transition was also observed during the monolayer cooling process at the π of 15 mN m-1. Based on SFM observation, we claimed that the molecular ordering or packing state in the rectangular lattice induced by cooling was better than that by the monolayer compression. Finally, the crystal transition mechanisms for these two procedures were proposed..
15. Atsushi Takahara, Yukiko Hara, Ken Kojio, Tisato Kajiyama, Characterization of the surface structural, mechanical, and thermal properties of benzocyclobutene dielectric polymers using scanned probe microscopy, Macromolecular Symposia, 10.1002/1521-3900(200103)167:1<213::AID-MASY213>3.0.CO;2-D, 2001.06, Scanning probe microscopy (SPM) techniques are used to characterize surfaces related to the processing of benzocyclobutene (BCB) dielectric thin films. Thermally cured resins and photodefineable resins are sold under the trade name CYLCOTENE™ 1) for electronic applications. TappingMode AFM (TMAFM) imaging is used to follow changes in adhesion promoter morphology upon baking to help explain adhesion performance. Power spectral density (PSD) analysis of TMAFM images of plasma treated BCB surfaces are unique and can be used to 'fingerprint' processes. Selective oxidation of the BCB surface can be used to fabricate a phase imaging standard for TMAFM. Near surface modulus of the BCB materials is 3.6 ± 0.2 GPa and the hardness is 0.38 ± 0.2 GPa measured by depth-sensing nanoindentation. Creep recovery of indents can be used to qualitatively distinguish between thermal and photocureable materials. A heated tip in a scanning thermal microscope can induce the thermal curing of BCB over micron sized areas. Local thermal analysis with the same probe allows the measurement of the changes in the glass transition, T g, at the surface with cure temperature..
16. Ken Kojio, Keiji Tanaka, Atsushi Takahara, Tisato Kajiyama, Novel method to prepare organosilane monolayers on solid substrate, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.74.1397, 2001.08, A novel and convenient method to prepare organosilane monolayers was proposed. Pure water was put onto a cleaned silicon wafer and then a toluene solution of n-trichloro(octadecyl)silane (OTS) was spread on it. X-ray photo-electron spectroscopy and atomic force microscopic observation revealed that an OTS monolayer was successfully formed on the solid substrate after the water was evaporated. The static water contact angle of the silicon wafer covered with the OTS monolayer was 105°. Molecular aggregation states of the OTS monolayer were examined by electron diffraction, Fourier transform infrared spectroscopic, X-ray reflectivity, and grazing incidence X-ray diffraction measurements. The prepared OTS monolayer was in a two-dimensional hexagonal crystalline state at 293 K and alkyl chains of the OTS molecules were oriented normal to the surface. Also, the alkyl chains in the monolayer were highly ordered, although the experimental procedure for the monolayer preparation was quite simple. The development of this novel method to prepare a low energy surface will contribute to the material science as well as having industrial applications..
17. 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 and Surfaces B: Biointerfaces, 10.1016/S0927-7765(01)00231-4, 2002.01, The n-octadecyltrichlorosilane (OTS, CH3(CH2)17SiCl3), 18-nonadecenyltrichlorosilane (NTS, CH2.CH(CH2)17SiCl3), [2-(perfluorooctyl)ethyl]trichlorosilane (FOETS, CF3(CF2)7CH2CH2SiCl 3) monolayers, and their mixed monolayers were used as model surfaces for the study of protein adsorption mechanism. Surface plasmon resonance (SPR) spectroscopy was applied to analyze the protein adsorption behavior onto the monolayer surfaces. The surfaces after exposure of these monolayers to bovine serum albumin (BSA) and γ-globulin(IgG) solutions were observed with atomic force microscope(AFM). AFM observation revealed that the charged protein either below or above pI was preferentially adsorbed onto the FOETS phase of the phase-separated (OTS/FOETS) mixed monolayer. in situ AFM observation of monolayer surfaces in BSA solution also revealed the preferential adsorption of BSA onto the hydrophobic FOETS surface. SPR clarified that the amount of adsorbed protein in the charged state was lower than that in the neutral state. Adhesion force was not detected in the force-distance curve measurement between negatively-charged HOOC(CH2)9SH chemisorbed cantilever tip and the OTS phase in the presence of adsorbed BSA on FOETS phase of mixed monolayer. These results indicate that the preferential adsorption of protein onto the FOETS phase for the mixed monolayer systems at either below or above pI is due to, (1) the minimization of interfacial free energy between the monolayer surface and the buffer solution; and (2) the electrostatic repulsion among protein molecules bearing charges..
18. K. Kojio, S. Jeon, S. Granick, Confinement-induced differences between dielectric normal modes and segmental modes of an ion-conducting polymer, European Physical Journal E, 10.1140/epje/i2001-10090-x, 2002.05, Dielectric measurement in the range 0.1 Hz to 1 MHz were used to study the motions of polymers and ions in an ion-conducting polymer, polypropylene oxide containing small quantities (on the order of 1%) of lithium ions (LiClO4), confined as a sandwich of uniform thickness between parallel insulating mica surfaces. In the dielectric loss spectrum, we observed three peaks; they originated from the normal mode of the polymer, segmental mode of the polymer, and ion motions. With decreasing film thickness, the peak frequencies corresponding to the normal mode and ion motion shifted to lower frequencies, indicating retardation due to confinement above 30 nm. This was accompanied by diminished intensity of the dielectric normal-mode relaxation, suggesting that confinement diminished the fluctuations of the end-to-end vector of the chain dipole in the direction between the confining surfaces. On the contrary, the segmental mode was not affected at that thickness. Finally, significant retardation of the segmental mode was observed only for the thinnest film (14 nm). The different dynamical modes of the polymer (segmental and slowest normal modes) respond with different thickness and temperature dependence to confinement..
19. Atsushi Takahara, Ken Kojio, Tisato Kajiyama, Effect of aggregation state on nanotribological behaviors of organosilane monolayers, Ultramicroscopy, 10.1016/S0304-3991(02)00100-6, 2002.08, Nanotribological behaviors of organosilane monolayers prepared by the Langmuir-Blodgett (LB) and chemisorption methods are discussed in terms of their aggregation states. Aggregation structure of the LB n-octadecyltrichlorosilane (OTS-C18) monolayers changed from a rectangular to an amorphous phase via a hexagonal phase with increasing temperature. A distinct lateral force decrease accompanies the phase transition. The LB alkyltrichlorosilane monolayers with longer alkyl chains were in a crystalline state at 293K. The lateral force of the LB alkyltrichlorosilane monolayers at 293K increased with increasing chain length. The n-triacontyltrichlorosilane LB monolayer (TATS-C30) in a rectangular phase showed higher lateral force than that of the alkyltrichlorosilane with shorter alkyl chains in a hexagonal phase. The lateral force of the OTS-C18 monolayer prepared by the LB method was higher than that of the chemisorbed one because of the higher packing density of alkyl chain for the LB monolayer, though both monolayers are in a hexagonal phase at 293K. A large increase in lateral force was observed for the 18-nonadecenyltrichlorosilane (NTS) after oxidation of vinyl end groups..
20. 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, 10.1295/polymj.35.44, 2003.03, Well-defined poly(methyl methacrylate) (PMMA) brush layers were prepared onto silicon wafers by surface-initiated atom transfer radical polymerization using 2-(4-chlorosulfonylphenyl)-ethyltrichlorosilane as an initiator. Based on molecular weight and layer thickness measurements, it was deduced that the apparent graft density was 0.6-0.8 chains nm-2 depending on the polymerization time and that the conformation of tethered chains was highly extended. Surface relaxation behavior of the PMMA brush layer and the spin-coated PMMA film was examined by lateral force microscopy. The αa- and β-relaxation processes were discernibly observed at both surfaces. Although surface molecular motion of the brush layer and the spin-coated film was markedly different from the bulk one, both were hardly distinguishable in terms of relaxation phenomena..
21. Mutsuhisa Furukawa, Yukinori Hamada, Ken Kojio, Aggregation structure and mechanical properties of functionally graded polyurethane elastomers, Journal of Polymer Science, Part B: Polymer Physics, 10.1002/polb.10628, 2003.10, Functionally graded polyurethane elastomers (FGPUEs) were prepared with two molds fixed at different temperatures (30 and 150°C). The effects of the molar ratio of the curing agent (60/40, 75/25, or 97/3 1,4-butane diol/1,1,1-trimethylol propane) and the molecular weight of the polymer glycol (number-average molecular weight = 2000 or 3000) on the molecular aggregation state and mechanical properties of the FGPUEs were investigated with differential scanning calorimetry, polarized optical microscopy, dynamic viscoelastic measurements, and tensile tests. The aggregation state of the FGPUEs was changed continuously from the one side (lower temperature side) to the other side (higher temperature side); for example, the glass-transition temperature gradually increased in this direction. Also, the number of spherulites formed in the FGPUEs increased in the same manner. In the mechanical tests, the tensile strength and elongation at break of the lower temperature side were higher than those of the higher temperature side. This was correlated with the strong phase separation of the lower temperature side. The poly(oxytetramethylene glycol)-based FGPUE with a chain extender of 75 wt% showed the largest degree of the temperature gradient..
22. Ken Kojio, Tomoya Fukumaru, Mutsuhisa Furukawa, Highly softened polyurethane elastomer synthesized with novel 1,2-bis(isocyanate)ethoxyethane, Macromolecules, 10.1021/ma0359988, 2004.05, A novel diisocyanate, 1,2-bis(isocyanate)ethoxyethane (TEGDI), whose backbone is ether bonds was used for the preparation of polyurethane elastomers (PUEs). 1,6-Hexamethylene diisocyanate (HDI) was also used as a control. The PUEs were prepared with either TEGDI or HDI, poly-(oxytetramethylene) glycol (PTMG), and curing agent by a prepolymer method. Differential scanning calorimetry, infrared spectroscopy, and wide-angle X-ray diffraction revealed that the phase separation of the network TEGDI-based PUEs was much weaker compared with that of the HDI ones. Highly softened TEGDI-based PUEs were successfully prepared on account of flexibility of TEGDI itself and weaker phase separation..
23. Ken Kojio, Sadaharu Nakamura, Mutsuhisa Furukawa, Effect of side methyl groups of polymer glycol on elongation-induced crystallization behavior of polyurethane elastomers, polymer, 10.1016/j.polymer.2004.09.061, 2004.11, Effect of side methyl and dimethyl groups of soft segment component on polyurethane elastomers (PUEs) was investigated with and without elongation. The polymer glycols used were poly(oxytetramethylene) glycol (PTMG), PTMG with dimethyl groups (PTG-X) and methyl groups (PTG-L). Phase separation of the PUEs became weaker with an increasing methyl group content. Tensile test revealed that the increasing methyl group concentration made the PUEs be soften and weaken. The PTMG based PUEs obviously exhibited elongation-induced crystallization during elongation process. In contrast, for the PTG-L and PTG-X based PUEs, crystallinity decreased with an increasing side methyl group content, and the PUEs with PTG-L and PTG-X with highest methyl group content did not crystallize. We succeeded the control of the crystallization behavior of elastomers under an elongation by the introduction of side methyl groups..
24. Tisato Kajiyama, Ken Kojio, Keiji Tanaka, Aggregation states and molecular motion of polymer ultrathin films prepared at the air/water interface, Advances in Colloid and Interface Science, 10.1016/j.cis.2004.09.007, 2004.12, The preparation of poly(amido amine) (PAMAM) dendrimer monolayers at the air/water interface was analyzed. Investigations show the transfer of PAMAM dedrimer monolayers from the air side onto hydrophobic silicon wafers, which were treated by the horizontal lifting method. X-ray reflectivity, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques were used to study the aggregation states in the PAMAM monolayers. The results show that the PAMAM molecules sit on the substrate with an oblate shape in which the hydrophilic core and hydrophobic alkyl end groups were towards the substrate and air sides..
25. Ken Kojio, Yoshiteru Nonaka, Tetsuo Masubuchi, Mutsuhisa Furukawa, Effect of the composition ratio of copolymerized poly(carbonate) glycol on the microphase-separated structures and mechanical properties of polyurethane elastomers, Journal of Polymer Science, Part B: Polymer Physics, 10.1002/polb.20303, 2004.12, Randomly copolymerized poly(carbonate) glycols were employed as starting materials for the synthesis of polyurethane elastomers (PUEs). The poly(carbonate) glycols had hexamethylene (C6) and tetramethylene (C4) units between carbonate groups in various composition ratios (C4/C6 = 0/100, 50/50, 70/30, and 90/10), and the number-average molecular weights of these poly(carbonate) glycols were 1000 and 2000. The PUEs were synthesized with these poly(carbonate) glycols, 4,4′-diphenyl-methane diisocyanate, and 1,4-butanediol by a prepolymer method. Differential scanning calorimetry measurements revealed that the difference between the glass-transition temperature of the soft segment in the PUEs and the glass-transition temperature of the original glycol polymer decreased and the melting point of the hard-segment domain increased with an increasing C4 composition ratio. The microphase separation of the polycarbonate) glycol-based PUEs likely became stronger with an increasing C4 composition ratio. Young's modulus of these PUEs increased with an increasing C4 composition ratio. This was due to increases in the degree of microphase separation and stiffness of the soft segment with an increase in the C4 composition ratio. The molecular weight of poly(carbonate) glycol also influenced the microphase-separated structure and mechanical properties of the PUEs. The addition of different methylene chain units to poly(carbonate) glycol was quite effective in controlling the microphase-separated structure and mechanical properties of the PUEs..
26. Mutsuhisa Furukawa, Yoshitaka Mitsui, Tomoya Fukumaru, Ken Kojio, Microphase-separated structure and mechanical properties of novel polyurethane elastomers prepared with ether based diisocyanate, polymer, 10.1016/j.polymer.2005.09.009, 2005.11, A diisocyanate baring ether bonds, 1,2-bis(isocyanate)ethoxyethane (TEGDI), was used for the preparation of polyurethane elastomers (PUEs). The PUEs were synthesized with either TEGDI or HDI, poly(oxytetramethylene) glycol (PTMG), and curing agents by a prepolymer method. 1,6-Hexamethylene diisocyanate (HDI) was also used as a control diisocyanate. The TEGDI-based PUEs exhibited highly softened property on account of flexibility of TEGDI itself and weaker phase separation. Another TEGDI-based PUEs were prepared with either poly(oxypropylene) glycol (PPG) or poly(caprolactone) glycol (PCL). Microphase-separated structure of these TEGDI-based PUEs are quite different from those with general diisocyanates and the PUEs were made be greatly softened..
27. Mutsuhisa Furukawa, Ken Kojio, Yasumitsu Sakamoto, Yoshie Minamida, Properties of fish protein-hydrophilic polymer hybrid gels, Polymer Bulletin, 10.1007/s00289-006-0612-5, 2007.01, Biogels and bio-hybrid gels were prepared from myofibril of fish and their properties were evaluated. The muscular protein used was extracted from fish meat. After washing and centrifugal separation, the muscular protein was mixed with 3 wt % of NaCl and the gels were prepared by heating the mixtures from 50 to 90 °C. The bio-hybrid gels were prepared from fish protein gel and poly(vinyl alcohol). Tensile tests revealed that the tensile strength, strain at break and Young's modulus of heated hybrid gels prepared at 50, 80 and 90 °C increased with increasing preparation temperature. This can be explained by the difference in crosslinking density. Also, the heated gels showed a good response to electric field in acid and alkaline solutions. Young modulus, tensile strength and elongation at break of the bio-hybrid gels increased with an increasing PVA content. Bending of hybrid gels in solutions of various pH under the electric stimulus was observed. The largest bending angle was 20-30 °C at pH=1.2..
28. Ken Kojio, Shohei Nakashima, Mutsuhisa Furukawa, Microphase-separated structure and mechanical properties of norbornane diisocyanate-based polyurethanes, polymer, 10.1016/j.polymer.2006.12.057, 2007.02, Norbornane diisocyanate (NBDI: 2,5(2,6)-bis(isocyanatomethyl)bicyclo[2.2.1]heptane) is a new commercialized diisocyanate. NBDI-based polyurethane elastomers (PUEs) were prepared from poly(oxytetramethylene) glycol (PTMG), NBDI and 1,4-butanediol (BD) by a prepolymer method. Microphase-separated structure and mechanical properties of the NBDI-based PUEs were compared with general aliphatic and cycloaliphatic diisocyanate-based PUEs. The diisocyanates used were isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (HMDI) and 1,6-hexamethylene diisocyanate (HDI). Regular polyurethanes were also prepared as hard segment models from each isocyanate and BD to understand the feature of each hard segment chain. The HDI-based PUE showed the largest Young's modulus and tensile strength in the four PUEs due to the ability of crystallization of the hard segment component and the strongest microphase separation. HMDI has both properties of aliphatic and cycloaliphatic diisocyanates because of its high symmetrical chemical structure compared with NBDI and IPDI. On the other hand, the NBDI- and IPDI-based PUEs have an inclination to phase mixing, leading to decreased Young's modulus and tensile strength. The NBDI-based PUE exhibited better thermal properties at high temperatures due to stiff structure of NBDI..
29. 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, 10.1021/ma0700577, 2007.04, The role of film thickness and interfacial interaction for controlling the size of microphase separation is described. XPS measurement was carried out to analyze the surface chemical composition of the PU films. The interdomain spacing of microphase-seaparated structure in the PU films were investigated by grazing incident small-angle X-ray scattering (GISAXS) measurement. As the film thickness decreases, the space for the crystallization of the hard segment chains become smaller. With decreasing film thickness, the size of the microphase-separated domains decrease, resulting in the amount of the interfacial region between hard segment domains and soft segment matrix increases. Fourier-transform infrared (FT-IR) spectra shows that the aggregation of the hard segment chains become weaker with decreasing film thickness. Strong polarity of the urethane groups leads to the strong interaction between the PU films and substrate surface, which results in the formation of the microphase-separated domain size..
30. Satoshi Yamasaki, Daisuke Nishiguchi, Ken Kojio, Mutsuhisa Furukawa, Effects of polymerization method on structure and properties of thermoplastic polyurethanes, Journal of Polymer Science, Part B: Polymer Physics, 10.1002/polb.21080, 2007.04, The effects of the dynamic polymerization method and temperature on the molecular aggregation structure and the mechanical and melting properties of thermo-plastic polyurethanes (TPUs) were successfully clarified. TPUs were prepared from poly (ethylene adipate) glycol (Mn = 2074), 4,4′-diphenylmethane diisocyanate and 1,4-butanediol by the one-shot (OS) and the prepolymer (PP) methods in bulk at dynamic polymerization temperatures ranging from 140 to 230°C. Glass-transition temperatures (Tgs) of the soft segment and melting points (Tms) of the hard segment domains of OS-TPUs increased and decreased, respectively, with increasing polymerization temperatures, but those of PP-TPUs were almost independent of the polymerization temperature. Tgs of the soft segment and T ms of the hard segment domains of these TPUs polymerized above 190°C were almost the same regardless of the polymerization method. Solid-state nuclear magnetic resonance spectroscopy (NMR) analyses of OS-and PP-TPUs showed that the relative proton content of fast decay components, which corresponds to the hard segment domains, in these TPUs decreased with increasing polymerization temperatures. These results clearly show that the degree of microphase separation becomes weaker with increasing polymerization temperatures. The temperature dependence of dynamic storage modulus and loss tangent of OS-TPUs coincided with those of PP-TPUs at polymerization temperature above 190°C. The apparent shear viscosity for OS- and PP-TPUs polymerized above 190°C approached a Newtonian behavior at low shear rates regardless of the polymerization method. These results indicate that TPUs polymerized at higher temperatures form almost the same molecular aggregation structures irrespective of the dynamic polymerization method..
31. Satoshi Yamasaki, Daisuke Nishiguchi, Ken Kojio, Mutsuhisa Furukawa, Effects of aggregation structure on rheological properties of thermoplastic polyurethanes, polymer, 10.1016/j.polymer.2007.06.006, 2007.07, The effects of the molecular aggregation structure on the rheological properties of thermoplastic polyurethane (TPU) were investigated. The TPU was composed of poly{(tetramethylene adipate)-co-(hexamethylene adipate)} glycol as the soft segments, 4,4′-diphenylmethane diisocyanate and 1,4-butanediol as the hard segments. The TPU sheets prepared by injection molding were annealed at various temperatures from 23 to 120 °C to vary the molecular aggregation structure. Glass transition temperature of the soft segment and melting points of the hard segment domains of the TPUs decreased and increased, respectively, with increasing annealing temperature. The results of DSC, solid-state NMR spectroscopy and dynamic viscoelastic measurements revealed that the degree of micro-phase separation of the TPUs becomes stronger with increasing annealing temperature due to the progress of formation of well-organized hard segment domains. The dynamic temperature sweep experiments for molten TPUs revealed that the temperature at critical gel point, which is defined as the temperature at which the dynamic storage modulus coincides with the loss storage modulus, in the cooling process increased with the progress of aggregation of the hard segments in the TPUs observed in the solid state. The uniaxial elongational viscosity measurements showed that TPUs exhibited an obvious strain hardening behavior with strain rate owing to residual hard segment domains at an operating temperature. It was revealed that the formation of well-organized hard segment domains had a profound effect on the rheological properties of TPUs, in particular on their elongational viscosity..
32. Ken Kojio, Microphase-separated structure of polar polymer ultrathin films, KOBUNSHI RONBUNSHU, 10.1295/koron.64.498, 2007.08, I investigated the specific chain structure of polyurethane (PU) films, which possess strong polar groups in the main chains and multiblock structure under confinement. The PU was synthesized from poly (oxytetramethylene) glycol (PTMG), 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD) by a prepolymer method. The hard segment contents were 20, 34 and 45 wt%. The ultrathin PU films were prepared onto a silicon wafer from a PU tetrahydrofuran solution by spin coating. The PU films exhibited microphase-separated structures, which are composed of hard segment domains surrounded by a soft segment matrix. For thicker films (∼200 nm), interdomain spacing almost corresponded to bulk value. On the other hand, it dramatically decreased for film thickness below 7 nm. This effect seems to be directly related to the decreasing film thickness. This is the first report, in which the phase-separated domain size of multiblock copolymers decrease with decreasing film thickness..
33. Mutsuhisa Furukawa, Ken Kojio, So Kugumiya, Yusuke Uchiba, Yoshitaka Mitsui, Microphase separation of bulk and ultrathin films of polyurethane elastomers, Macromolecular Symposia, 10.1002/masy.200850702, 2008.06, Polyurethane elastomers (PUEs) were synthesized with poly(oxytetramethylene) glycol (PTMC), 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD)/1,1,1-trimethylol propane (TMP) by a prepolymer method. The degree of microphase separation of bulk and ultrathin films for these PUEs was confirmed by Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and atomic force microscopy (AFM). In the bulk films, FT-IR and DSC measurements revealed that the degree of micro-phase separation strengthened with increasing BD content. AFM observation of the BD-PUE showed hard segment domains surrounded by a soft segment matrix. The domains ranged in size from 10-20 nm, while BD/TMP- and TMP PUEs did not have clear domains. On the other hand, AFM observation was carried out on thin films (200 mm in thickness) and ultrathin films (approximately 8-5 nm) prepared by spin-coating the different concentrations of PUE solutions. The microphase separated strucuture under 10 nm in thickness showed marked decreases in the size of the microphase-separated domain..
34. Ken Kojio, Sadaharu Nakamura, Mutsuhisa Furukawa, Effect of side groups of polymer glycol on microphase-separated structure and mechanical properties of polyurethane elastomers, Journal of Polymer Science, Part B: Polymer Physics, 10.1002/polb.21540, 2008.10, The effect of side methyl and dimethyl groups of the soft segment component on the microphase-separated structure and mechanical properties of Polyurethane elastomers (PUEs) was investigated. Poly(oxytetramethylene) glycol (PTMG), and PTMG incorporating dimethyl groups (PTG-X) and methyl side groups (PTG-L) were used as a polymer glycol, which forms a soft segment in the PUEs. The PUEs were synthesized with 4,4′-dipheylmethane diisocyanate [1, 1′- methylenebis(4-isocyanatobenzene)], 1,4-butane diol, and 1,1,1-trimethylol propane by a prepolymer method. The degree of microphase separation of the PUEs became weaker with increasing side group content in polymer glycols. Dynamic viscoelastic properties measurement showed reorganized-crystallization and melting of the soft segment for the PUEs based on PTMG, PTG-L, and PTG-X with a lower content of the side groups, but not for a PTG-L and PTG-X with higher content of the side groups. Tensile testing revealed that increasing methyl group concentration made the PUEs soften and weaken. The PTMG-based PUEs obviously exhibited strain-induced crystallization of the soft segment chains during elongation process. In contrast, for the PTG-L and PTG-X-based PUEs, crystallinity decreased with increasing side group content, and the PUEs with PTG-L and PTG-X with highest methyl group content did not crystallize even at a large strain..
35. Ken Kojio, Microphase-separated structure and rheological properties of polyurethanes, Nihon Reoroji Gakkaishi, 10.1678/rheology.36.229, 2008.12, A novel diisocyanate, 1,2-bisisocyanate ethoxyethane (TEGDI) whose backbone is ether bonds, was used for the preparation of polyurethane elastomers (PUEs). Highly softened TEGDI-based PUEs were successfully prepared on account of flexibility of TEGDI itself and weaker phase separation. A relationship between conformation and molecular mobility of the soft segment were investigated using dynamic viscoelastic measurement. The peaks of α relaxation of the soft segment chains were clearly observed in the loss tangent (tan δ) curves at various strains. The onset temperature of α relaxation decreased with increasing strain. This result indicates that the size of cooperative motion of the glass transition decreased due to the orientation of the soft segment chains with increasing strain. The effect of the microaggregation structure on the rheological properties of thermoplastic polyurethane (TPU) were investigated. The TPUs showed the strain hardening of uniaxial elongation viscosity with increasing annealing temperature owing to residual hard segment domains at an operating temperature. It was revealed that the formation of well-organized hard segment domains had a profound effect on the rheological properties of TPUs, in particular on their elongational viscosity..
36. Ken Kojio, Yusuke Uchiba, Yasunori Yamamoto, Suguru Motokucho, Mutsuhisa Furukawa, Chain and mirophase-separated structures of ultrathin polyurethane films, Journal of Physics: Conference Series, 10.1088/1742-6596/184/1/012028, 2009.01, Measurements are presented how chain and microphase-separated structures of ultrathin polyurethane (PU) films are controlled by the thickness. The film thickness is varied by a solution concentration for spin coating. The systems are PUs prepared from commercial raw materials. Fourier-transform infrared spectroscopic measurement revealed that the degree of hydrogen bonding among hard segment chains decreased and increased with decreasing film thickness for strong and weak microphase separation systems, respectively. The microphase-separated structure, which is formed from hard segment domains and a surrounding soft segment matrix, were observed by atomic force microscopy. The size of hard segment domains decreased with decreasing film thickness, and possibility of specific orientation of the hard segment chains was exhibited for both systems. These results are due to decreasing space for the formation of the microphase-separated structure..
37. Baiju John, Suguru Motokucho, Ken Kojio, Mutsuhisa Furukawa, Polyamide 6 fibers with superior mechanical properties
TPU coating techniques
, Journal of Fiber Science and Technology, 10.2115/fiber.65.236, 2009.01, Thermoplastic polyurethane (TPU) was thin film coated on polyamide 6 (PA6) fibers by the reactive bulk and solution coating techniques. The thickness of the coating was 40 um for the reactive bulk coating technique and 20 μm for the solution coating. The increase in crystallinity, the formation of the interface interaction region and the entry of TPU thin film coating into the micro-cracks under tensile stress resulted in the increase of strength as well as elongation of the TPU coated PA6 fibers. The microphase separated-structure and the orientation of the hard segment domains of the TPU thin film coating on the PA6 fiber surface had an impact on the force alignment of the PA6 fiber when under a mechanical stress. The hard segment domains of the TPU thin film which was prepared by a solution coating technique showed better alignment to the deformation force direction compared to the reactive bulk based one. This led to better mechanical strength of the former based TPU coated PA6 fiber. The TPU is a son material and the improvement of mechanical property with same should be specially noted. So an understanding of both type of coating techniques is very useful in various industrial applications of PA6 fibers..
38. Ken Kojio, So Kugumiya, Yusuke Uchiba, Yuichi Nishino, Mutsuhisa Furukawa, The microphase-separated structure of polyurethane bulk and thin films, Polymer Journal, 10.1295/polymj.PJ2008186, 2009.04, The microphase-separated structure of polyurethane bulk and thin films were investigated using atomic force microscopy (AFM). The polyurethane (PUs) were synthesized with poly(oxytetramethylene) glycol (PTMG), 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD) by a prepolymer method. The hard segment contents were 34 and 45wt%. Polarized optical microscopy (POM) revealed that the 34wt% PUE is homogeneous at a macroscopic level, while the 45wt% one is macrophase-separated into two phases. One phase forms spherulites of ca. 2-5 urn in diameter. AFM observation for the 34 wt % PUE showed the microphase-separated structure, consisting of hard segment domains and a soft segment matrix. In contrast, for the 45 wt % PUE, a lot of the hard segment domains were observed in the spherulite region, indicating that spherulites include much amount of hard segment component, in contrast, outside of spherulite exhibited similar structure to that of 34 wt % one. For the PU bulk, the different microphase-separated structure in the inside and outside of spherulite was successfully observed for the first time. Also, the microphase-separated structure of PU films was investigated as a function of the film thickness. The PU films exhibited similar microphase-separated structure. For the thicker film (-200nm), the interdomain spacing almost corresponded to bulk one. On the other hand, that for the film thickness below 7nm dramatically decreased. This seems to be simply related to a decreasing space. We obtained the experimental data, which the phase-separated domain size of multiblock copolymer decreased with decreasing film thickness..
39. Baiju John, Ken Kojio, Mutsuhisa Furukawa, High performance polyamide 6 fibers using polycarbonate based thermoplastic polyurethane thin film Coatings- A novel method, Polymer Journal, 10.1295/polymj.PJ2008286, 2009.07, Polycarbonate based thermoplastic polyurethanes (CPU2) were prepared and coated onto polyamide 6 (PA 6) fibers. The CPU2 thin film coatings were prepared by dipping the PA 6 fibers into a viscous CPU2 adduct and cured at 100 °C for 12 h. Both the tensile strength and the elongation at break of the CPU2 thin film coated PA 6 fibers (CPU2-PA6) increased although both the magnitudes of CPU2 are much lower than for the original PA 6 fibers. FE-SEM observation revealed that ; there existed an interface interaction region of 10 um at the interface of PA 6 fiber and the CPU2 thin film coating. Generally , speaking, it is considered that the break of PA 6 fibers is due to the formation of the micro-cracks on the fiber surface when it is under a tensile load. The coating of CPU2 onto the PA 6 fibers reduced the formation of micro-cracks during the elongation process, resulted in the improvement of the mechanical properties. Also, the CPU2-PA6 fibers when exposed to weathering i• tests to check the weathering resistance, showed an increase in the tensile strength for 0-50 h of exposure. This was due to the ; UV light induced crystalline transformation, i.e., from the a crystalline phase to the y crystalline phase. The CPU2-PA6 fibers j I almost retained the strength even after 200 h of exposure in a weatherometer. The crystalline transformations due to the UV 't irradiations have not been reported yet. Also, the CPU2 showed good adhesion property with the PA 6 films. The blending i with various polymers or composites is generally employed for the performance enhancement of PA 6 fibers. On the contrary, the method employed in this study improved the performance of PA 6 fibers without changing its inherent morphological properties..
40. Ken Kojio, Yoshitaka Mitsui, Mutsuhisa Furukawa, Synthesis and properties of highly hydrophilic polyurethane based on diisocyanate with ether group, polymer, 10.1016/j.polymer.2009.05.030, 2009.07, Highly hydrophilic polyurethane elastomers (PUEs) were synthesized from 1,2-bis(isocyanate) ethoxyethane (TEGDI), poly(ethylene oxide-co-propylene oxide) copolyol (EOPO) and 1,4-butane diol/1,1,1-trimethylol propane (75/25) (wt/wt) by a prepolymer method. 4,4′-Diphenylmethane diisocyanate (MDI)-based PUEs were synthesized as a control as well. Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) measurements revealed that the degree of microphase separation of the TEGDI-based PUEs was much weaker than for the MDI-based PUEs. Young's modulus and elongation at break of the TEGDI-based PUEs were quite lower and larger than for the MDI-based PUEs, respectively. This is due to quite weak cohesion force of the hard segment chains in the TEGDI-based PUEs. The degree of swelling of the TEGDI-based PUEs was five times larger than for the MDI-based one. This is associated with the hydrophilic nature of TEGDI and weak cohesion force in the TEGDI-based PUEs..
41. 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, 10.1002/app.30047, 2009.08, Spherulite size graded polyurethane elastomers (PUEs) were prepared using a mold with a temperature gradient from different polymer glycols, 4,40-diphenylmethane diisocyanate (MDI) and a mixture of 1,4-butanediol (BD), and 1,1,1-trimethylol propane (TMP) as a curing agent by a prepolymer method. The used polymer glyocols were poly(oxytetramethylene)glycol (PTMG, M n = 2000), poly(ethylene adipate)glycol (PEA, Mn = 2000), and poly(hexamethylene adipate)glycol (PHA, Mn = 2000). The effect of polyether and polyester glycols and the temperature gradient on the micro-aggregation structure and mechanical properties were studied by polarized optical microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, micro-hardness test, pulsed nuclear magnetic resonance spectroscopy, and tensile test. The prepared PUEs had spherulite size graded super-structure. Spherulite sizes of the PUEs depended significantly on the temperature gradient of the mold. Spherulite of the PUEs in contact with the mold at low temperature was significantly smaller and more dense than that contacting the mold at high temperature. The spherulite diameter of PTMG-, PEA-, and PHA-PUEs changed from 12.6 to 16.3 m̈m, 8.4 to 15.6 m̈m, and 10.4 to 16.0 m̈m, respectively from the lower temperature side (LTS) toward the higher temperature side. In contrast, the number of spherulites became sparser toward the higher one. The glass transition temperature (Tg) of PTMG-, PEA-, and PHA-based PUEs elevated from -55.3°C, -19.0°C and -33.8°C at the LTS to -48.6°C, -17.8°C and -32.8°C at the HTS, respectively. Tg of all PUEs exhibited elevation from the LTS toward the higher one. This result associated with the strong microphase separation of the LTS..
42. Ken Kojio, Shun Matsumura, Takuya Komatsu, Shuhei Nozaki, Suguru Motokucho, Mutsuhisa Furukawa, Kohji Yoshinaga, Microphase-separated structure and dynamic viscoelastic properties of polyurethanes elastomers prepared at various temperatures and cross-linking agent contents, Nihon Reoroji Gakkaishi, 10.1678/rheology.42.143, 2014, The relationship between a microphase-separated structure and dynamic viscoelastic properties of polyurethane elastomers (PUEs) prepared at various temperatures and cross-linking agent contents were investigated. The PUEs were synthesized with poly(oxytetramethylene) glycol (PTMG), 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD) and a mixture of BD and 1,1,1-trimethylol propane (TMP) by a prepolymer method. The PUEs are in the strong-segregation limit. The microphase-separated structure was investigated using Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), small-angle x-ray scattering (SAXS) and atomic force microscope (AFM). The extent of microphase separation of the PUEs became stronger and weaker with increases in curing temperature and trifunctional TMP content, respectively. The consistent results obtained in this study would be quite helpful to design the desirable PUEs..
43. Kohji Yoshinaga, Yin Yang, Teruhisa Ohno, Suguru Motokucho, Ken Kojio, Inclusion of fullerene in polymer chains grafted on silica nanoparticles in an organic solvent, Polymer Journal, 10.1038/pj.2014.24, 2014.01, We successfully achieved inclusion of fullerene (C60) into the grafted-poly(MMA-NMA) chains in THF without inducing the formation of C60 clusters and/or aggregation between the polymer-grafted silica particles. Polymer grafting onto silica was conducted by reacting 12nm colloidal silica particles with polymeric silane, prepared by radical polymerization, in THF without particle aggregation. Molecules of C60 were effectively included into grafted polymer chains in the THF suspension of the poly(MMA-NMA)-grafted silica, prepared from polymers with molecular weights of 33 200 and 48 000, without the formation of C60 clusters and without aggregation between the silica composite particles. It was observed that the maximum C60inclusion into poly(MMA-NMA) chains grafted on 11.2 mg silica particles was 0.25 mg, corresponding to 2.7 C60 molecules per unit SiO2 particle..