Aromatic Polymer with Pendant Perfluoroalkyl Sulfonic Acid for Fuel Cell Applications

Novel proton exchange membranes were prepared and investigated as polymer electrolyte membranes (PEMs) for polymer electrolyte membrane fuel cells (PEMFCs). Polymers having poly(arylene ether sulfone) in the main chain and −CF 2 CF 2 OCF 2 CF 2 SO 3 H in the side chain (PES-PSA) were synthesized by dehalogen coupling of poly{oxy-4,4′-(3,3′-dibromobiphenylene)oxy-4,4′-diphenylsulfone} (PES-Br) and potassium 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoro-2- iodoethoxy)ethanesulfonate (PSA-K) using copper metal, followed by treatment with aqueous HCl. The proton conductivity of PES-PSA with an ion exchange capacity (IEC) of 1.58 mmol/g was 0.12 S/cm at 80 °C under 90% relative humidity. PES-PSA with an IEC of 1.34 mmol/g was used as the membrane for PEMFC, and the maximum power output at 80 °C was 805 mW/cm 2 when fully humidified hydrogen and air were provided. A DMA measurement and a tensile test revealed that PES-PSA had a higher α-relaxation temperature than Nafion and higher flexibility than sulfonated polyethersulfone (SPES).