Tailoring ion networks of block-graft copolymers using click chemistry for high-performance hydrocarbon polymer electrolyte membranes

To address the environmental and economic concerns associated with perfluorinated sulfonic acids (PFSAs), we propose a novel approach to synthesize block-graft copolymers for hydrocarbon polymer electrolyte membranes (PEMs) designed for clean energy applications including fuel cells and water electrolysis. This study introduces an efficient “graft-onto” approach using click chemistry, which couples side chains onto a main polymer backbone, enabling the precise structural construction of block-graft copolymers. This method allows the formation of long side chains and enables stepwise tuning of ionic channel through adjustments of the graft degree. Our membrane, poly(styrene-b-ethylene-co-butylene-b-styrene)-graft-triazole-poly(styrene sulfonic acid) (SEBS-g-TzPSSA, referred to as Click SgP) exhibited a highly ordered, microphase-separated morphology. The Click SgP membranes achieved record-high ion conductivities even at low ion exchange capacity (IEC) values. Their well-defined nanostructure, coupled with extended side chains, provided enhanced mechanical stability and elongation properties while efficiently regulating water uptake and minimizing swelling. Unlike conventional hydrocarbon PEMs, the Click SgP membranes were successfully employed in a large-scale, mass-production-compatible decal transfer method for fabricating membrane electrode assemblies (MEAs). This study explores vapor sorption, ion transport, and electrochemical performance, highlighting the pivotal role of click chemistry in developing advanced nanostructured polymer architectures.