Polymer electrolyte membranes having sulfoalkyl grafts into ETFE film prepared by radiation-induced copolymerization of methyl acrylate and methyl methacrylate

Hanh, T. T.*; Takahashi, Shuichi; Chen, J.; Sawada, Shinichi; Maekawa, Yasunari

Polymer electrolyte membranes (PEMs) containing alkylsulfonic acid grafts can be prepared by radiation-induced graft copolymerization of methyl acrylate (MA) and methyl methacrylate (MMA) into a poly(ethylene-co-tetrafluoroethylene) (ETFE) film followed by sulfonation of the MA units in the copolymer grafts using an equimolar complex of chlorosulfonic acid and 1,4-dioxane (ClSOH-Complex). The grafted films with 33-79 % MA units are treated with ClSOH-Complex to obtain PEMs with IEC of 0.36-0.81 mmol/g and proton conductivity of 0.04-0.065 S/cm. The PEMs with higher MMA content showed higher durability in water (80 C) and under oxidative conditions (3% HO) at 60 C. This is because the PMMA grafts in the PEMs have no proton at an -carbonyl carbon, which is considered to be a trigger of the degradation of grafting polymers.