Amphiphilic Phosphonated-Fluorinated Block Copolymer-Modified PFSA (Perfluorosulfonic Acid) Membranes with Enhanced Proton Conductivity

Amphiphilic block copolymers containing hydrophilic phosphorylcholine segments and fluorinated methacrylate segments were incorporated into perfluorosulfonic acid (PFSA) membranes via solution blending and casting to improve proton transport. The resulting PFSA/PMPCF-x composite membranes exhibit good structural stability and interfacial compatibility, accompanied by slight modification of the membrane microstructure and reduced crystallinity. The PFSA/PMPCF-6 membrane with 1 wt % additive achieves a proton conductivity of 214 mS cm–1 at 80 °C and 100% RH. Notably, significantly enhanced conductivity is observed under low-humidity conditions, reaching 28.88 mS cm–1 at 80 °C and 50% RH, corresponding to a 6.73-fold increase over pristine PFSA. The improvement is mainly attributed to the hygroscopic and water-retention capability of the phosphorylcholine groups. Membrane electrode assembly tests further demonstrate improved device performance. This work provides a practical strategy for improving the PFSA membrane performance under low-humidity conditions and offers useful insights for the design of advanced proton exchange membranes.