Abstract

Anion exchange membranes (AEMs) having polyvinylimidazolium grafts were synthesized by radiation-induced graft polymerization of N-vinylimidazole (NVIm) or the coplymerizaiton with styrene onto poly(ethylene-co-tetrafluoro-ethylene) (ETFE) film, followed by N-alkylation and ion exchange reactions. The alkaline durability of the membranes was evaluated in 1M KOH at 60 and 80{degree sign}C. The AEM consisting of the homopolymer and copolymer (1:1 molar ratio) grafts (AEM2 and AEM3) with the ion exchange capacity (IEC) of 0.86 and 1.18 mmol g-1 exhibited ionic conductivity of 23 and 63 mS cm-1, respectively. The homopolymer-type AEM2 showed alkaline stability at 60 {degree sign}C for 270 hours, but degraded at 80 {degree sign}C for ca. 150 hours. In contrast, the copolymer-type AEM3 kept its ion conductivity above 10 mS cm-1 in 1M KOH at 80 {degree sign}C for 250 h. The alkylimidazolium group in the copolymer grafts is a promising anion exchange group in AEMs for highly alkaline durable fuel cells.

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