Low-temperature crosslinking of anion exchange membranes

Abstract

This paper reports crosslinked anion exchange membranes using a low temperature olefin metathesis crosslinking scheme. Styrene-based block and random copolymers bearing benzyl chloride or benzyl trimethyl quaternary ammonium chloride groups were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. The crosslinked AEMs were prepared from styrene-based block copolymers with alkene pendant groups through crosslinking metathesis via Grubbs 2^nd generation catalyst. The covalent crosslinking afforded robust mechanical properties in dry materials and low water uptake and small dimensional change for the hydrated membranes, even at high ion exchange capacity (IEC). The crosslinked membranes showed good conductivity when in contact with liquid water, but had lower conductivity than samples of uncrosslinked AEMs under relative humidity hydration conditions. The morphologies of crosslinked AEMs as investigated by SAXS showed correlation with their conductivity values.