Synthesis of copolymer grafts containing sulfoalkyl and hydrophilic groups in polymer electrolyte membranes

Enomoto, Kazuyuki; Takahashi, Shuichi; Rohani, R.; Maekawa, Yasunari

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 80C 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.