Synthesis and properties poly(arylene ether sulfone)s with pendant hyper-sulfonic acid

A new class of poly(arylene ether sulfone) with multiple sulfonic acid groups on aromatic side chains (PAES-nS, n = 2 or 3) were prepared from hydroxyphenyl-containing polymer precursors and sulfonated monomer by graft reaction. Those polymers were soluble in the common organic solvents, such as DMAc, DMF, DMSO and NMP, exhibited good thermal stability, the glass transition temperatures ranged from 200 to 240 °C and the 5% weight loss temperatures were higher than 290 °C. Remarkably, all the PAES-nS membranes exhibited high proton conductivity above 10−2 S cm−1 at room temperature, and low swelling ratio below 26% at 80 °C. Compared with Nafion 117, the PAES-3S-40 with high ion exchange capacity (IEC) value (1.89 mequiv. g−1) exhibited higher proton conductivity and appropriate swelling ratio at the same conditions. A combination of good thermal stability, excellent dimensional stability and high proton conductivities indicates these polymers are good candidate materials for proton exchange membrane in fuel cell applications.