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Enomoto, Kazuyuki; Takahashi, Shuichi; Rohani, R.; Maekawa, Yasunari
Journal of Membrane Science, 415-416, p.36 - 41, 2012/10
Times Cited Count：15 Percentile：46.12(Engineering, Chemical)Polymer electrolyte membranes (PEM) consisting of ion conducting alkylsulfonic acid and hydroxyl groups were successfully synthesized by radiation-induced graft polymerization of vinyl acetate (VAc) into a poly(ethylene-
-tetrafluoroethylene) (ETFE) film, followed by alkylsulfonation with 1,3-propanesulfone. The prepared PEM showed higher conductivity under 30% relative humidity at 80
C than that of the conventional poly(styrenesulfonic acid)-grafted ETFE. Furthermore, the prepared PEM also showed better mechanical properties than those of Nafion. Thus, the PEM with hydroxyl groups possesses sufficient mechanical and electrochemical properties, required for a fuel cell, operating at a high temperature and low humidity.
Rohani, R.*; Yamaki, Tetsuya; Koshikawa, Hiroshi; Takahashi, Shuichi*; Hasegawa, Shin; Asano, Masaharu; Maekawa, Yasunari; Voss, K.-O.*; Trautmann, C.*; Neumann, R.*
Nuclear Instruments and Methods in Physics Research B, 267(3), p.554 - 559, 2009/08
Times Cited Count：14 Percentile：66.94(Instruments & Instrumentation)We investigated how pretreatment and high-LET beam irradiation affected the ion-track dissolution rate in poly(vinylidene fluoride) (PVDF) films by SEM observations and conductometric analysis in order to develop the preparation methodology of nano-sized ion-track membranes. PVDF thin films irradiated with four types of ion beams were exposed to a 9 M KOH aqueous solution after their storage in air at 120C. This heating treatment was found to enhance the etch rate in the latent track, both in the inner core and outer halo regions, without changing that in the bulk, probably due to the formation of parasitic oxidation products facilitating the introduction of the etching agent to improve the etchability. Additionally, the irradiation of heavier higher-LET ions, causing each track to more activated sites (like radicals), was preferable for achieving effective etching.
Yamaki, Tetsuya; Rohani, R.*; Koshikawa, Hiroshi; Takahashi, Shuichi; Hasegawa, Shin; Asano, Masaharu; Voss, K.-O.*; Neumann, R.*; Maekawa, Yasunari
Kobunshi Rombunshu, 65(3), p.273 - 276, 2008/03
Times Cited Count：3 Percentile：10.77(Polymer Science)Poly(vinylidene fluoride) thin films irradiated with four kinds of ion beams were exposed to a 9 M KOH aqueous solution after their storage in air for 30 or 90 days at different temperatures. According to the conductometry, the heating at 120ºC was found to enhance the etch rate in the latent track without changing that in the bulk, thereby enabling us to obtain very high etching sensitivity for the preparation of nano-sized through-pores. The formation of hydroperoxides during this pretreatment should facilitate the introduction of the etching agent to improve etchability. Additionally, the irradiation of higher-LET ions, causing each track to more activated sites (like radicals), was preferable to achieve high sensitivity of the etching.
Enomoto, Kazuyuki; Takahashi, Shuichi; Rohani, R.*; Maekawa, Yasunari
no journal, ,
The polymer electrolyte membranes consisting grafted sulfoalkyl ether on ETFE film were prepared. Grafting of vinyl acetate into the irradiated ETFE was carried out under Ar at 40 C. The grafting degrees increased with increasing an irradiation dose. The basic hydrolysis of poly(vinyl acetate) units in the grafting chain led to poly(vinyl alcohol) (PVA) in good yields. The sulfoalkylation of the hydroxyl group in the grafted PVA with 1,3-propanesultone was performed. A ring-opening reaction of 1,3-sultone induced by the nucleophilic addition of PVA gives sulfoalkyl ether in 70% yield. The ATR-IR spectrum of the membrane shows new peaks at 3369, 1647, and 1032 cm
, which are assigned to sulfoalkyl ether. The SEM-EDS image of the membrane shows a homogenous distribution of S atoms. The ion exchange capacity and proton conductivity of the membrane are estimated to be 1.6 mequiv g and 0.12 S cm, which are high enough for a fuel cell application.
Koshikawa, Hiroshi; Yamaki, Tetsuya; Rohani, R.*; Takahashi, Shuichi*; Hasegawa, Shin; Asano, Masaharu; Maekawa, Yasunari
no journal, ,
Poly(vinylidene fluoride) thin films irradiated with four kinds of ion beams were exposed to a 9 M KOH aqueous solution after their storage in air for 30 or 90 days at different temperatures. According to the conductometry, the heating at 120C was found to enhance the etch rate in the latent track without changing that in the bulk, thereby enabling us to obtain very high etching sensitivity for the preparation of nano-sized through-pores. The formation of hydroperoxides during this pretreatment should facilitate the introduction of the etching agent to improve etchability. Additionally, the irradiation of higher-LET ions, causing each track to more activated sites (like radicals), was preferable to achieve high sensitivity of the etching.
