Fluorine-induced Microphase Separation & Acid Redistribution: A Dual-regulation Strategy toward High Temperature Proton Exchange Membranes with Broad-temperature Adaptability and Exceptional Durability

Advanced high-temperature proton exchange membranes (HT-PEMs) demand integrated broad-temperature adaptability and operational stability to fulfill the stringent requirements of industrial applications. The strategic construction of microphase-separate architectures within membrane emerges as a viable approach to simultaneously extend the operational temperature window and enhance mechanical-chemical stability HT-PEMs. This study developed poly( p -terphenyl imidazole) membranes incorporating acid-phobic fluorinated 3,3’-difluoro-1,1’-biphenyl (BP2F) units via superacid-catalyzed polyhydroxyalkylation. The membrane maintains enhanced proton conductivity and requires lower proton transport activation energy even when containing low PA doping level (ADL), revealing that proton transport mechanisms rely not merely on ADL, but crucially on fluorine-induced microphase separation and PA redistribution. The membrane containing 15 wt% BP2F demonstrated exceptional proton conductivity (145.11 mS cm -1 at 180 o C and 47.26 mS cm -1 at 80 o C) and fuel cell performance (1019 mW cm -2 peak power density at 180 o C and 310 mW cm -2 peak power density at 80 o C), while exhibiting remarkable stability under accelerated stress testing (4.5% power density decay after 200 cycles at 180 o C). This study successfully enhanced the formation of microphase-separated structures in polymers and improved fuel cell performance through the strategic incorporation of fluorinated acid-phobic units.