Fluorine-Free Synthesis and Optimization of Graft Polymer Proton Exchange Membranes for Enhanced Water Electrolysis Performance

An aromatic graft polymer was synthesized for use as a proton exchange membrane (PEM) by grafting a highly sulfonated poly(phenylene sulfide sulfone) side chain onto a poly(arylene ether sulfone) main chain, resulting in a phase-separated morphology with continuous hydrophilic ion channels. This structure provided low hydrogen permeability and high proton conductivity, alongside excellent dimensional, mechanical, and thermohydrolytic stability, making it highly suitable for demanding water electrolysis environments. The graft PEM demonstrated superior performance in proton exchange membrane water electrolysis (PEMWE). Additionally, an investigation into the structure-property relationship showed that longer side chains reduced swelling and permeability during high-temperature water immersion, optimizing the graft PEM for water electrolysis applications. This highlights the potential of the graft PEM for efficient use in fluorine-free PEMWE systems.