Sulfonated poly(arylene sulfone) multiblock copolymers for proton exchange membrane fuel cells

We report herein aromatic multiblock copolymers (sPAS-A/Bs) consisting of sulfonated hydrophilic poly(arylene sulfone) blocks combined with hydrophobic poly(arylene ether sulfone) blocks. The synthesis involved polycondensation reactions of sulfonated and non-sulfonated oligomers, coupling reactions between these oligomers to produce the precursor copolymers based on sulfonated poly(arylene thioether sulfone)s (sPTS-A/Bs), followed by their oxidation to the corresponding sPAS-A/Bs. Thus, the sulfonated poly(arylene sulfone) blocks were chosen as the hydrophilic part due to their high chain stiffness, strong acidity, and resistance against desulfonation. The sPAS-A/B membranes showed well-connected hydrophilic nanophase domains, an increased thermal and oxidative stability, and decreased water uptake compared to the corresponding sPTS-A/B membranes. At 80 °C and 50% relative humidity (RH), sPAS-A/B membranes showed a high proton conductivity of 0.028 S/cm, which was comparable to that of Nafion 212 and far exceeded those of the parent sPTS-A/B membranes. Moreover, the sPAS-A/B membranes showed high cell performance of 826 mA/cm2 at low humidity (@ 0.6 V, 70 °C, 50% RH) and great durability over 1200 h in open circuit voltage hold test (80 °C, 10% RH). Because of their superior transport and stability properties, the sPAS-A/B membranes hold tremendous potential to fulfill the demands of proton exchange membrane fuel cells.