Synthesis and properties of poly(arylene ether nitrile) with pendant bisulfonic acid for proton exchange membrane application

A new class of poly(arylene ether nitrile) with a bisulfonated phenyl ring on the side chains (PAEN-bS) was prepared from a hydroxybenyl-containing polymer precursor and a bisulfonated monomer by applying graft reaction. The polymers were soluble in common organic solvents such as dimethylsulfoxide (DMSO, purity>99.5%; Sinopharm Chemical Reagent Co., Ltd, Shanghai, China), N,N-dimethylacetamide (DMAc, purity>99.0%; Sinopharm Chemical Reagent Co., Ltd, Shanghai, China), dimethylformamide (DMF, purity>99.0%; Sinopharm Chemical Reagent Co., Ltd), and 1-methyl-2-pyrrolidinone (NMP, purity>99.0%; Sinopharm Chemical Reagent Co., Ltd) and showed good thermal stability, with a 5% weight loss and temperature higher than 320°C. Remarkably, all the PAEN-bS membranes showed a high proton conductivity of more than 10？2 S cm？1 at room temperature and a low swelling ratio of less than 20% at 100°C; in particular, the conductivity of the PAEN-Bs-60 polymer membrane with the highest ion exchange capacity value was higher than that of Nafion 117 at all test temperature ranges. The combination of good thermal stability, excellent dimensional stability, and high proton conductivity indicates that these polymers are good candidate materials for proton exchange membranes in fuel cell applications