Novel Wholly Aromatic Sulfonated Poly(arylene ether) Copolymers Containing Sulfonic Acid Groups on the Pendants for Proton Exchange Membrane Materials

A series of novel wholly aromatic sulfonated poly(arylene ether) copolymers containing sulfonic acid groups on the pendants [SC-SPAE, i.e., side-chain-type sulfonated poly(arylene ether)] were prepared by direct copolymerization of sulfonated monomer [sodium 4-(4-(2,6-difluorobenzoyl)phenoxy) benzenesufonate (SDFBS)], 4,4‘-dichlorodiphenyl sulfone (DCDPS), and 4,4‘-dihydroxyldiphenylether (DHDPE). The sulfonate degree (DS) of the copolymers was readily controlled by adjusting the feed ratio of SDFBS to DCDPS. Structures of the sulfonated copolymers were confirmed by FT-IR and NMR. Tough and flexible films of the wholly aromatic copolymers with good thermal and oxidative stability were obtained by solvent cast process in N,N-dimethylacetamide (DMAc) solution. The films of these side-chain-type copolymers show good dimensional stability, and their water uptake and swelling ratios at high temperature are lower than those of the main-chain-type sulfonated poly(arylene ether) with similar ion exchange capacity...