Proton exchange membranes prepared by simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene) films. II. Properties of sulfonated membranes

Proton exchange membranes were prepared by radiation-induced grafting of st yrene onto commercial poly(tetrafluoroethylene-co-hexafluoropropylene) film s using a simultaneous irradiation technique followed by a sulfonation reac tion. The resulting membranes were characterized by measuring their physico chemical properties such as water uptake, ion exchange capacity, hydration number, and proton conductivity as a function of the degree of grafting. Th e thermal properties (melting and glass transition temperatures) and therma l stability of the membrane were also investigated using differential scann ing calorimetry and thermal gravimetric analysis, respectively. Membranes h aving degrees of grafting of 16% and above showed proton conductivity of th e magnitude of 10(-2) Ohm (-1) cm(-1) at room temperature, as well as therm al stability at up to 290 degreesC under an oxygen atmosphere. (C) 2000 Joh n Wiley & Sons, Inc.