Side-chain-type poly(arylene ether sulfone)s containing multiple quaternary ammonium groups as anion exchange membranes

Abstract A new difluorodiphenyl sulfone monomer, 3,3′,5,5′-tetra(3′′,5′′- dimethylphenyl)-4,4′-difluorodiphenyl sulfone (M-DFDPS), was synthesized and further polymerized to form a series of poly(arylene ether sulfone)s containing four pendent 3,5-dimethylphenyl groups. After bromination of benzylmethyl groups, side-chain-type poly(arylene ether sulfone)s containing multiple quaternary ammonium groups in pendant phenyl rings (PAES-Q-xx) were prepared by quaternization. Their chemical structures and some properties, including water uptake, swelling ratio, hydroxide conductivities, and thermal and alkaline stabilities, were investigated. These PAES-Q-xx membranes with IEC values of 1.65–2.36 mequiv/g had low water uptake and swelling ratio. Their conductivities were all above 10 mS/cm and the values were in the range of 23–37 and 54–82 mS/cm at 20 and 80 °C, respectively. The good conductivity is probably due to the high IEC and the dense distribution of the pendant quaternary ammonium groups. In addition, PAES-Q-xx membranes also displayed good thermal and alkaline stabilities.