Enhancement of hydroxide conduction by self-assembly in anion conductive comb-shaped copolymers

Abstract

An anion exchange membrane (AEM) was prepared from comb-shaped copolymers bearing locally and densely functionalized side chains. In this study, we synthesized the graft copolymer of bromomethylated poly(phenylene oxide)-graft-quaternary ammonium functionalized 4-vinylbenzyl chloride (BPPO-g-QVBC), using an activator regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) of QVBC from a BPPO macroinitiator. The BPPO-g-QVBC graft copolymers with a combination of a high graft density and appropriate graft length present advanced materials for AEMs. Flexible and transparent membranes were obtained by casting the polymers from NMP solutions, and displayed a microphase-separated morphology with nano-sized ionic clusters embedded in the hydrophobic BPPO matrix. Accordingly, the resultant membranes show considerably high conductivities, up to 0.1 S cm⁻¹ at 80 °C, derived from the special polymer architecture. This study gives some pioneering insights and directions from the viewpoint of macromolecular design to prepare highly conductive AEMs.