Alkaline stable anion exchange membranes based on poly(phenylene-co-arylene ether ketone) backbones

Abstract

To improve the alkaline stability of anion exchange membranes (AEMs) based on conventional poly(ether ketone/sulfone) backbones, two novel poly(phenylene-co-arylene ether ketone) (PPAEK) ionomers with a quaternary ammonium (QA-) or imidazolium (IM-) group were prepared by zero-valent nickel-catalyzed coupling polymerization, benzylic bromination and in situ amination, successively. In particular, the cationic head-groups were incorporated as pendants into the polyphenylene moieties. Due to its higher water uptake and well-developed microphase separations, IM-PPAEK exhibited a better ion conduction ability than QA-PPAEK over the entire temperature range. However, QA-PPAEK displayed significantly higher alkaline stability in a 1 M NaOH aqueous solution at 80 °C, i.e., over 80% of its initial ion conductivity was still maintained after 1000 h of testing. The present work provides a promising new synthetic approach to obtain high performance AEMs based on chemically stable polyphenylene units.