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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：13 Percentile：41.91(Polymer Science)Hamada, Takashi; Hasegawa, Shin; Fukasawa, Hideyuki*; Sawada, Shinichi; Koshikawa, Hiroshi; Miyashita, Atsumi; Maekawa, Yasunari
Journal of Materials Chemistry A, 3(42), p.20983 - 20991, 2015/11
Times Cited Count：36 Percentile：70.44(Chemistry, Physical)no abstracts in English
Chen, J.; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Applied Polymer Science, 100(6), p.4565 - 4574, 2006/06
Times Cited Count：44 Percentile：75.19(Polymer Science)This study concerns a comparative study of three crosslinkers, divinylbenzene (DVB), 1,2-bis(p,p-vinylphenyl)ethane (BVPE) and triallyl cyanurate (TAC) crosslinked poly(ethylene-co-tetrafluoroethylene) (ETFE)-based radiation-grafted membranes, which were prepared by radiation grafting of p-methylstyrene (MeSt) onto ETFE films and subsequent sulfonation. The effect of the different types and contents of the crosslinkers on the grafting and sulfonation, and the properties such as water uptake, proton conductivity and thermal/chemical stability of the resulting polymer electrolyte membranes was investigated in detail. Introducing crosslink structure into the radiation-grafted membranes leads to a decrease in proton conductivity due to the decrease in water uptake. The thermal stability of the crosslinked radiation-grafted membranes is also somewhat lower than that of the noncrosslinked one. However, the crosslinked radiation-grafted membranes show significantly higher chemical stability characterized in the 3% H
O at 50
C. Among the three crosslinkers, the DVB shows a most pronounced efficiency on the crosslinking of the radiation-grafted membranes, while the TAC has no significant influence; the BVPE is a mild and effective crosslinker, showing the moderate influence between the DVB and TAC crosslinkers.
Chen, J.; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Materials Science, 41(4), p.1289 - 1292, 2006/02
Times Cited Count：22 Percentile：57.69(Materials Science, Multidisciplinary)The MeSt/tBuSt/DVB-grafted polymer electrolyte membrane showed a high performance for the fuel cell applications. The tBuSt contributed the high chemical stability while the MeSt contributed the high conductivity to the resulted membrane. The DVB crosslinker in the membrane further improved the chemical stability. The new polymer electrolyte membrane with a degree of grafting of 36% showed proton conductivity as high as the Gore-Select membrane, and the durability time was about 3 times longer than that of the traditional styrene/DVB-grafted one. Therefore, the MeSt/tBuSt/DVB-grafted polymer electrolyte membrane was more possible to be used for the fuel cells.
Chen, J.; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Membrane Science, 269(1-2), p.194 - 204, 2006/02
Times Cited Count：141 Percentile：95.90(Engineering, Chemical)To develop a highly chemically stable polymer electrolyte membrane for application in a direct methanol fuel cell (DMFC), four styrene derivative monomers, m,p-methylstyrene (MeSt), p-tert-butylstyrene (tBuSt), divinylbenzene (DVB) and bis(p,p-vinyl phenyl) ethane (BVPE) were graft copolymerized into poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by sulfonation and hydrolysis. The latter two monomers were used as crosslinkers. The graft copolymerization was carried out by the 
-ray preirradiation method. The influence of the preirradiation dose and the grafting kinetics were investigated in detail. Sulfonation of the grafted ETFE films was performed in a chlorosulfonic acid solution, by which the sulfonation ratio reached about 90%. The newly obtained membrane possesses significantly higher chemical stability than the traditional styrene/DVB-grafted membrane and six times lower methanol permeability compared to the Nafion 112 membrane. Therefore, this study reveals the possibility of the developed inexpensive four monomers-grafted membranes, which could provide an attractive alternative as a substitute for the expensive Nafion membranes for DMFC applications.
Sawada, Shinichi; Yamaki, Tetsuya; Asano, Masaharu; Terai, Takayuki*; Yoshida, Masaru
Transactions of the Materials Research Society of Japan, 30(4), p.943 - 946, 2005/12
We synthesized crosslinked-polytetrafluoroethylene (PTFE) electrolyte membranes by a radiation grafting technique under different conditions, and then investigated their proton conduction properties at controlled temperatures and relative humidities (R.H.) by an AC impedance method. The density and length of graft chains were controlled by varying the pre-irradiation dose and grafting time, respectively. When the pre-irradiation dose was fixed at 15 kGy to make the graft chains an uniform density, the elongation of the graft chain increased the ion exchange capacity (IEC), there by enhancing their proton conductivity. The membrane with an IEC of 2.8 meq/g possessed the maximum conductivity reaching 0.20 S/cm at 80 C and R.H. 95%. At almost the same IEC, membranes with more and shorter graft chains showed higher conductivity than those with less and longer chains. This result was probably related to the different structures of hydrophilic domains as proton-conducting pathways.
Maekawa, Yasunari
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Maekawa, Yasunari
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Maekawa, Yasunari
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