Comb-shaped 2-Methylimidazolium Poly(arylene ether sulfone) Anion Exchange Membranes with High Alkaline Stability

A series of comb-shaped poly(arylene ether sulfone)s containing pendant 2-methyl-3-alkylimidazolium group(ImPAES-Cx, x=1, 6, 10) was prepared and characterized as novel anion exchange membranes. These Im-PAES-Cx membranes were obtained by benzylic bromination and imidazolium functionalization. The characteristic nano-phase separation structure was formed in membranes with longer alkyl side chains, as confirmed by small-angle X-ray scattering. The nano-phase separation structures endowed ImPAES-Cx membranes with improved ionic conductivity, dimensional stability(at least 60% decrease water uptake and swelling ratio at 60 °C) and mechanical properties, together with excellent alkaline stability. Especially, ImPAES-C6 membranes possessed enhanced hydroxide conductivity and chemical stability simultaneously. These results suggest that it is a feasible strategy to introduce appropriate length of alkyl side chains into anion exchange membranes(AEMs) to improve the performance.