Synthesis and Properties of Novel Side-Chain Sulfonated Poly(Arylene Ether Sulfone)s for Proton Exchange Membranes

A series of novel side-chain sulfonated poly(arylene ether sulfone) (SPAES) multiblock and random copolymers were synthesized by condensation polymerization from a new disulfonated aryl sulfone monomer, 4,4′-difluoro-2,2′-bis(3-sulfobenzoyl)diphenyl sulfone disodium salt (DFBSPS). The chemical structures of DFBSPS and the SPAESs were characterized by proton nuclear magnetic resonance (¹H NMR) and Fourier transform infrared (FTIR) spectra. The SPAES membranes prepared by solution cast method exhibited high tensile strength (50–71 MPa) and high radical oxidative stability. They could keep their morphology and maintain proton conductivities after hydrolysis test in 95 °C water for 1000 h. They also showed smaller swelling ratio in in-plane direction than in through-plane direction and such an anisotropic effect was more significant for the multiblock copolymers than for the random ones. The multiblock copolymer membranes exhibited higher proton conductivity than the random ones with similar ion exchange capacities (IECs). Preliminary hydrogen-oxygen fuel cell tests were performed at 60 °C and 80% relative humidity (RH). The results showed that the single cell equipped with the multibiock copolymer membrane SB3 exhibited 0.12 W cm⁻² higher maximum output power density than the one equipped with the random copolymer membrane SR3 (with the same IEC), indicating much better performance of the former.