Synthesis and Characterization of a Side-chain Type Sulfonated Poly (arylene ether sulfone) s for Proton Exchange Membranes

A novel active difluoro sulfone monomer,3,3'-bis (phenoxyphenyl)-4,4'-difluorodiphenyl sulfone, was successfully synthesized through free-radical substitution and Suzuki coupling reactions using 4,4'-difluorodiphenyl sulfone and N-bromosuccinimide (NBS) as starting materials. Then it was employed to prepare a series of poly (arylene ether sulfone)s (PAES-xx) with 4,4'-difluorodiphenyl sulfone and 4,4'-dihydroxybenzophenone via nucleophilic polycondensation reaction. Poly(arylene ether sulfone) s proton exchange membranes (SPAES-xx) were obtained by mild post-sulfonation reaction and solution casting. The structures and properties of these membranes were investigated. The results showed that the SPAES-xx membranes displayed moderate water absorption and good dimensional stability, and the highest proton conductivity of membranes reached 0.16 S/cm at 80 degrees C. Moreover, these membranes showed good thermal stability and mechanical properties. The onset weight loss temperatures of SPAES-xx were approximately 250 degrees C. They had tensile strengths of 29.5 similar to 42.0 MPa, tensile modulus of 0.62 similar to 1.23 GPa, and elongations to break from 9.0% to 31.9%. Excellent comprehensive properties of SPAES-xx membranes were mainly ascribed to the introduction of side-chain sulfonated structure and the formation of well defined hydrophilic/hydrophobic phase separation structure.