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Journal Articles

Elucidation of the morphology of the hydrocarbon multi-block copolymer electrolyte membranes for proton exchange fuel cells

Zhao, Y.; Yoshida, Miru*; Oshima, Tatsuya*; Koizumi, Satoshi*; Rikukawa, Masahiro*; Szekely, N.*; Radulescu, A.*; Richter, D.*

Polymer, 86, p.157 - 167, 2016/03

 Times Cited Count:10 Percentile:47.96(Polymer Science)

Journal Articles

Molecular dynamics simulation of telomeric single-stranded DNA and POT1

Kaburagi, Masaaki; Yamada, Hironao*; Miyakawa, Takeshi*; Morikawa, Ryota*; Takasu, Masako*; Kato, Takamitsu*; Uesaka, Mitsuru*

Polymer Journal, 48(2), p.189 - 195, 2016/02

 Times Cited Count:4 Percentile:73.91(Polymer Science)

We performed molecular dynamics (MD) simulations of telomeric single-stranded DNA and POT1 for 100 ns. The distance between $$C_alpha$$ (POT1) and O5' (telomeric ssDNA) is calculated to verify the binding system for 100 ns MD. We then calculated the distance between the bases of telomeric DNA ends and the root mean square deviation and gyration radius in single and binding states. We compared the root mean square fluctuations between single and binding states and calculated the number of hydrogen bonds between POT1 and telomeric DNA. There are many hydrogen bonds between Gln94 and the first guanine of the closest TTAGGG sequence in telomeric single-stranded DNA. These Gln94 and the guanine have a large difference in root mean square fluctuation between single and binding states. We found that Gln94 and guanine are important components of the binding system, and they are related to its stability.

Journal Articles

Combining small-angle and intermediate-angle neutron scattering to study the hierarchical structure in microbial cellulose

Zhao, Y.; Koizumi, Satoshi

European Polymer Journal, 66, p.437 - 443, 2015/05

 Times Cited Count:2 Percentile:89.21(Polymer Science)

Journal Articles

Dependence of structure of polymer side chain on water structure in hydrogels

Sekine, Yurina; Takagi, Hajime*; Sudo, Sayoko*; Kajiwara, Yutaro*; Fukazawa, Hiroshi; Fukazawa, Tomoko*

Polymer, 55(24), p.6320 - 6324, 2014/11

 Times Cited Count:13 Percentile:46.24(Polymer Science)

To investigate the effects of structure of polymer side chains on structure of water in hydrogels, Raman spectra of polyacrylamide (PAA) and poly-$$N$$,$$N$$-dimethylacrylamide (PDMAA) hydrogels were measured. PAA and PDMAA have similar chemical structures, except for the side chain structure. The result shows that the frequency of the OH stretching mode for the PAA hydrogel decreases as the water content decreases, while that for the PDMAA hydrogel increases. We conclude that most of the bound water molecules in the PAA hydrogel form four strong hydrogen bonds with the hydrophilic groups in the side chain of PAA, whereas those in the PDMAA hydrogel form weak hydrogen bonds with surrounding water molecules. The water structure is an important factor governing the physical and chemical properties of gel materials.

Journal Articles

Pulse radiolysis study on a highly sensitive chlorinated resist ZEP520A

Hosaka, Yuji*; Oyama, Tomoko; Oshima, Akihiro*; Enomoto, Satoshi*; Washio, Masakazu*; Tagawa, Seiichi*

Journal of Photopolymer Science and Technology, 26(6), p.745 - 750, 2013/12

 Times Cited Count:8 Percentile:69.41(Polymer Science)

ZEP520A is one of the most popular positive electron beam (EB) resists used in research and photomask fabrication owing to its excellent properties. Herein, EB-induced initial reactions of ZEP520A were investigated via pulse radiolysis (EB energy: 28 MeV, time resolution: 10 ns). Dissociative electron attachment and formation of a charge transfer complex were definitive contributing factors to the efficient degradation of ZEP520A. Furthermore, products induced by direct ionization of ZEP520A were observed in a highly concentrated ZEP520A solution in tetrahydrofuran, suggesting that initial reactions in the ZEP520A solid film that are induced only by direct ionization could be simulated via pulse radiolysis in specific solutions.

Journal Articles

Graft-type polymer electrolyte membranes for fuel cells prepared through radiation-induced graft polymerization into alicyclic polybenzimidazoles

Park, J.*; Takayama, Toshio*; Asano, Masaharu; Maekawa, Yasunari; Kudo, Kazuaki*; Takayama, Toshio*

Polymer, 54(17), p.4570 - 4577, 2013/08

 Times Cited Count:5 Percentile:78.3(Polymer Science)

Graft-type sulfonated polybenzimidazole was prepared through radiation-induced graft polymerization of styrenes into an alicyclic polybenzimidazole film and subsequent sulfonation. The alicyclic polybenzimidazole, ChPBI, was prepared from $$trans$$-1,4-cyclohexanedicarboxylic acid and 3,3'-diaminobenzidine using typical polycondensation. Anisotropic domains with a size of several tens of micrometers were found in the ChPBI films casted from LiCl-containing $$N$$,$$N$$-dimethylacetamide. Irradiation of the ChPBI membranes with a 220 kGy dose of $$gamma$$-rays created radical species with mean lifetimes of two days. The treatment of this membrane with a 50/50 (v/v) mixture of 1-propanol and styrene produced polystyrene graft chains. Sulfonation of the resulting grafted membrane with ClSOH$$_{3}$$OH occurred selectively on the polystyrene grafts. The sulfonated films showed proton conductivity on the order of 10$$^{-3}$$ to 10$$^{-2}$$ S/cm with an ion exchange capacity between 2.1 and 2.9 mmol/g. SEM-EDX analysis of the membrane indicated the presence of macrophase separated domains up to 1 $$mu$$m in diameter. The proton conductivity of the membrane did not decrease for 600 h at 120$$^{circ}$$C in liquid water.

Journal Articles

Nanoscale structures of radiation-grafted polymer electrolyte membranes investigated via a small-angle neutron scattering technique

Sawada, Shinichi; Yamaguchi, Daisuke; Putra, A.; Koizumi, Satoshi*; Maekawa, Yasunari

Polymer Journal, 45(8), p.797 - 801, 2013/08

 Times Cited Count:5 Percentile:78.3(Polymer Science)

The nanoscale structures of graft-type polymer electrolyte membranes based on poly(ethylene-co-tetrafluoroethylene) (ETFE) films were investigated using a small-angle neutron scattering (SANS) technique. For comparison, SANS measurements were also performed on two precursor materials, the original ETFE film and polystyrene (PS)-grafted films. The SANS profiles of the grafted films showed shoulder peaks at a d-spacing of approximately 30 nm, which were attributed to the PS grafts introduced into the amorphous phases between the ETFE lamellar crystals. In the ETFE PEMs, the spacing of the polystyrene sulfonic acid (PSSA) grafts and ETFE crystals increased because the graft regions were enlarged by the volume of the attached sulfonic acid groups. Interestingly, the graft / crystal stack spacing in the PEMs did not increase from the dry- to fully-hydrated states. This finding implies restricted water absorption in the PSSA grafts between the ETFE lamellar crystals.

Journal Articles

Effects of crosslinker density on the polymer network structure in poly-$$N$$,$$N$$-dimethylacrylamide hydrogels

Fukazawa, Tomoko*; Ikeda, Naohiro*; Tabata, Mayu*; Hattori, Masataka*; Aizawa, Mamoru*; Yunoki, Shunji*; Sekine, Yurina

Journal of Polymer Science, Part B; Polymer Physics, 51(13), p.1017 - 1027, 2013/07

 Times Cited Count:21 Percentile:31.38(Polymer Science)

Journal Articles

Crystal morphology-dependent graft polymerization in poly(ether ether ketone) films

Hasegawa, Shin; Takahashi, Shuichi*; Iwase, Hiroki*; Koizumi, Satoshi; Onuma, Masato*; Maekawa, Yasunari

Polymer, 54(12), p.2895 - 2900, 2013/05

 Times Cited Count:7 Percentile:69.41(Polymer Science)

Radiation-induced graft polymerization of sulfo-containing styrene derivatives into crystalline poly(ether ether ketone) (PEEK) substrates was carried out to prepare thermally and mechanically stable polymer electrolyte membranes based on an aromatic hydrocarbon polymer, so-called "super-engineering plastics". Graft polymerization of the sulfo-containing styrene, ethyl 4-styrenesulfonate (E4S) into PEEK substrates with degrees of crystallinity (DC) of 11 - 26% gradually progressed, achieving a grafting degree of more than 50% after 72 hours, whereas graft polymerization of the substrates with DC above 26% did not proceed. When morphological change in these films were measured by SAXS, PEEK films with DC larger than 26% showed a new peak at d=14 nm, corresponding to lamella structure. Thus, the suppression of graft polymerization of PEEK films with DC above 26% was due to obstruct of monomer diffusion by the formation of the oriented lamella structure.

Journal Articles

Effect of partial delignification of kenaf bast fibers for radiation graft copolymerization

Mohamed, N. H.*; Tamada, Masao; Ueki, Yuji; Seko, Noriaki

Journal of Applied Polymer Science, 127(4), p.2891 - 2895, 2013/02

Changes in residual lignin of kenaf bast fiber with acidic chlorite using various parameters were conducted to produce partial delignified fiber for radiation graft copolymerization. The effect of delignification temperature, operating time as well as chlorite doses on the residual lignin of the fibers has been reported. Results obtained indicated that the optimal delignification was achieved at 80$$^{circ}$$C for 6h with 0.5% chlorite. The reduction in density, size and tensile strength were attributed to the increase of removal of lignin from the fiber. Radiation induced emulsion graft copolymerization of 4-chloromethyl styrene (CMS) on partial delignified kenaf with residual lignin $$<$$2% resulted in higher degree of grafting of about 143% as compared to the undelignified fiber, which showed the absence of grafting degree.

Journal Articles

$$gamma$$-ray irradiated organic thin film transistors based on perfluoropentacene with polyimide gate insulator

Takayanagi, Yutaro*; Ouchi, Hirokuni*; Duan, Z.*; Okukawa, Takanori*; Yanagi, Yuichiro*; Yoshida, Akira*; Taguchi, Mitsumasa; Hirao, Toshio; Nishioka, Yasushiro*

Journal of Photopolymer Science and Technology, 25(4), p.493 - 496, 2012/08

 Times Cited Count:0 Percentile:100(Polymer Science)

Organic thin film fields effect transistors are expected to be used in spacecrafts/satellites because they can realize large-size, mechanical flexibility, light weight and low-cost devices. N-channel field effect transistors with a Si/polyimide(PI)/perfluoropentacene/Au structure were fabricated, and irradiated with $$gamma$$-ray from Co source. The changes of the drain current vs. source/drain voltage characteristics were measured after every 200 Gy in silicon Gy(Si) irradiations up to the total dose of 1200 Gy(Si). The drain current gradually increased up to the total dose of 1200 Gy(Si). The threshold voltage decreased up to 400 Gy(Si), and gradually recovered above 600 Gy(Si). The mobility was almost unchanged up to 1200 Gy(Si). Those behaviors were explained by accumulation of positive trapped charge within the gate insulator PI near the interface. Evidence for the accumulation of interface traps was hardly observed.

Journal Articles

Microprocessing of arched bridge structures with epoxy resin by proton beam writing

Takano, Katsuyoshi*; Asano, Atsushi*; Maeyoshi, Yuta*; Marui, Hiromi*; Omichi, Masaaki*; Saeki, Akinori*; Seki, Shu*; Sato, Takahiro; Ishii, Yasuyuki; Kamiya, Tomihiro; et al.

Journal of Photopolymer Science and Technology, 25(1), p.43 - 46, 2012/07

 Times Cited Count:2 Percentile:91.32(Polymer Science)

Journal Articles

Surface modification of vulcanized rubber by radiation grafting, 2; Improvement in performance of wiper rubber

Mizote, Norihito*; Katakai, Akio; Tamada, Masao

Journal of Applied Polymer Science, 123(4), p.2172 - 2176, 2012/02

 Times Cited Count:3 Percentile:87.1(Polymer Science)

Surface of natural rubber was modified by radiation-induced grafting of 2-hydroxyethyl methacrylate (HEMA) to improve the properties of surface hardness, dry friction, wiping performance, and wear duration. The composition ration of HEMA to rubber was controlled from 0.29 to 0.93 by changing HEMA concentration and dose in graft polymerization. When this composition ration was higher than 0.7, the surface hardness was higher than 64 and the coefficient of dry friction lower than 0.65. Those values became better than those of commercially available chlorinated-rubber in terms of wear and friction against glass. The resulting wear resistance was 10 times higher than chlorinated rubber. However, the surface hardness in wet state was 62.5 since grafted-HEMA gave the hydrophilicity to the rubber. As a result, the grafted-HEMA rubber realized 95% and higher wiping performance of water on glass.

Journal Articles

Synthesis and characterization of carboxymethyl derivatives of kappa-carrageenan

Tranquilan-Aranilla, C.*; Nagasawa, Naotsugu; Bayquen, A.*; Dela Rosa, A.*

Carbohydrate Polymers, 87(2), p.1810 - 1816, 2012/01

 Times Cited Count:54 Percentile:7.64(Chemistry, Applied)

Carboxymethyl derivatives of kappa-carrageenan (KC) with varying degrees of substitution were obtained by multi-step carboxymethylation process. The structural and chemical profiles of the derivatives were determined by FTIR, $$^{13}$$C NMR, gel permeation chromatography, elemental analysis, potentiometric titration and visual estimation of gelation temperature. The derivatives exhibited high degrees of substitution and acidity. However, sulfur content, molecular weight and gelation temperature were lower compared to the parent KC polymer. FTIR confirmed the presence of carboxymethyl groups in the polymer backbone while $$^{13}$$C NMR revealed that functionalization occurred at the three hydroxyl groups in KC disaccharide unit.

Journal Articles

Structure and dynamics of poly(vinyl alcohol) gels in mixtures of dimethyl sulfoxide and water

Kanaya, Toshiji*; Takahashi, Nobuaki; Takeshita, Hiroki*; Okura, Masatoshi*; Nishida, Koji*; Kaji, Keisuke*

Polymer Journal, 44(1), p.83 - 94, 2012/01

 Times Cited Count:11 Percentile:55.88(Polymer Science)

Journal Articles

Thermoresponsive extraction of cadmium(II) ions by poly(TPEN-NIPA) gels; Effect of chain length and branched spacer structure on gel formation and extraction behavior

Inaba, Yusuke*; Tsumagari, Takayuki*; Kida, Tatsuya*; Watanabe, Wataru*; Nakajima, Yasutaka*; Fukuoka, Sachio*; Mori, Atsunori*; Matsumura, Tatsuro; Nakano, Yoshio*; Takeshita, Kenji*

Polymer Journal, 43(7), p.630 - 634, 2011/07

 Times Cited Count:11 Percentile:57.53(Polymer Science)

${it N,N,N',N'}$-(tetrakis-2-pyridylmethyl)ethylenediamine (TPEN) derivatives bearing a polymerizable double bond in the substituent structure of the pyridine ring are synthesized and subjected to copolymerization with ${it N}$-isopropylacrylamide in the presence of AIBN. The obtained poly(TPEN-NIPA) gels show thermo-responsive swelling/shrinking behaviors and are employed for the extraction of cadmium(II) ion from the aqueous solution to examine the relationship of the gel characteristics and the extraction performance. The polymer gels composed of the TPEN derivative bearing C3, C4, C10 and branched C3 spacer chains are synthesized and temperature-dependent extraction behavior of cadmium ion is compared. These gels extract Cd(II) ion efficiently from the aqueous solution in the swelling state at 5$$^{circ}$$C, while little extraction is observed at 45$$^{circ}$$C with shrinking. It is found that poly(TPEN-NIPA) gel of branched C3 spacer (C3b) shows the excellent thermoresponsive extraction performance.

Journal Articles

The Static structure of polyrotaxane in solution investigated by contrast variation small-angle neutron scattering

Endo, Hitoshi; Mayumi, Koichi*; Osaka, Noboru*; Ito, Kozo*; Shibayama, Mitsuhiro*

Polymer Journal, 43(2), p.155 - 163, 2011/02

 Times Cited Count:5 Percentile:78.85(Polymer Science)

Polyrotaxane (PR) possesses a supramolecular structure in which cyclic molecules are threaded into an axial polymer. In this study, the static structure of PR dissolved in a good solvent was investigated using contrast variation small-angle neutron scattering. The conformation of the axial linear polymer and the alignment of cyclic molecules within the axial polymer were evaluated quantitatively with the help of a detailed derivation of scattering theory. The decomposed partial scattering functions of the cyclic molecules and the axial polymer and the cross-correlation between cyclic molecules and an axial polymer strongly supported the idea that the alignment of cyclic molecules threaded on the axial polymer is random. On the basis of experimental observation, the entropic origin of the stiffening of PR due to the array of cyclic molecules is discussed.

Journal Articles

Radiation-induced graft polymerization of functional monomer into poly(ether ether ketone) film and structure-property analysis of the grafted membrane

Hasegawa, Shin; Takahashi, Shuichi*; Iwase, Hiroki*; Koizumi, Satoshi; Morishita, Norio; Sato, Ken*; Narita, Tadashi*; Onuma, Masato*; Maekawa, Yasunari

Polymer, 52(1), p.98 - 106, 2011/01

 Times Cited Count:40 Percentile:16.35(Polymer Science)

Radiation-induced graft polymerization of sulfo-containing styrene derivatives into poly(ether ether ketone) (PEEK) substrates was carried out to prepare thermally and mechanically stable polymer electrolyte membranes based on an aromatic hydrocarbon polymer. Graft polymerization of ethyl 4-styrenesulfonate into a 32% crystallinity degree PEEK substrate hardly progressed, whereas graft polymerization into 11% PEEK substrate gradually progressed, achieving a grafting degree of more than 50% after 72 h. From Electron Spin Resonance analysis of irradiated PEEK films, it apparent the graft polymerization initiate from the phenoxy radicals. Small-angle X-ray scattering and small-angle neutron scattering observations clearly showed that the graft-type PEEK membranes possessed ion channel domains with the average distance of 13 nm, being larger than that of Nafion. Furthermore, there was a micro-structure in the ion channels with the average distance of 1.8 nm.

Journal Articles

Preirradiation graft polymerization of styrene in a poly(tetrafluoroethylene) film investigated by time-resolved small-angle neutron scattering

Iwase, Hiroki*; Sawada, Shinichi; Yamaki, Tetsuya; Maekawa, Yasunari; Koizumi, Satoshi

International Journal of Polymer Science, 2011(2011), p.301807_1 - 301807_7, 2011/00

 Times Cited Count:8 Percentile:67.34(Polymer Science)

Preirradiation graft polymerization of styrene in a poly(tetrafluoroethylene) (PTFE) film was examined by time-resolved small-angle neutron scattering (SANS). A crosslinked PTFE film, thickness of which is about 50$$mu$$m, was irradiated by $$gamma$$-ray and immersed in a mixed solvent of styrene monomer and toluene. SANS elucidated that graft polymerization proceeds by two reaction processes (I) and (II). In process (I) at 0$$<t<$$200 min, graft polymerization occurs at an interface between crystalline and amorphous PTFE domains and the grafted polystyrene segregates from PTFE, forming a thin layer with a sharp interface. In process (II) at 200$$<t<$$600 min, grafted PS layer starts to bridge between crystalline domains. At the end of process (II), 40% of total crystalline PTFE domain is covered by the grafted PS chains.

Journal Articles

Modification of a hydrophobic-ligand-containing porous sheet using tri-$$n$$-octylphosphine oxide, and its adsorption/elution of bismuth ions

Tanaka, Ryota*; Ishihara, Ryo*; Miyoshi, Kazuyoshi*; Umeno, Daisuke*; Saito, Kyoichi*; Asai, Shiho; Yamada, Shinsuke*; Hirota, Hideyuki*

Reactive and Functional Polymers, 70(12), p.986 - 990, 2010/12

 Times Cited Count:7 Percentile:66.05(Chemistry, Applied)

352 (Records 1-20 displayed on this page)