Poly(ether sulfone) copolymers containing densely quaternized oligo(2, 6-dimethyl-1, 4-phenylene oxide) moieties as anion exchange membranes

Abstract

Anion exchange membranes (AEMs) with phase-separated morphologies were prepared by brominating poly(ether sulfone) copolymers with oligo(2, 6-dimethyl-1, 4-phenylene oxide) moieties, followed by quaternization and ion exchange. By this synthetic strategy, quaternary ammonium groups were densely and selectively introduced into oligo(phenylene oxide) moieties. Small angle X-ray scattering patterns of quaternized poly(ether sulfone) with oligo(2, 6-dimethyl-1, 4-phenylene oxide) segments (QPES-co-PPO) showed obvious ionic peaks, whereas no peak was observed for quaternized poly(phenylene oxide) (QPPO) homo-polymers. The properties of these AEMs were studied according to their water uptake, hydration numbers, conductivities, mechanical properties, alkaline stability. In comparison with QPPO-based AEMs with similar ion exchange capacities, AEMs based on QPES-co-PPO showed markedly higher conductivity. This could be ascribed to the existence of ionic clusters stemmed from their phase-separated morphologies.