Synthesis and characterization of novel fluorinated poly(arylene ether sulfone)s containing pendant sulfonic acid groups for proton exchange membrane materials

Abstract

A series of new fluorinated poly(arylene ether sulfone) (BPAQSH-XX) copolymers were prepared by potassium carbonate mediated direct copolymerization of 4,4′-bis(4′-fluoro-3′-trifluoromethyl benzyl) biphenyl (QBF), 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (SDCDPS) and 4,4′-isopropylidene diphenol (BPA). The degree of sulfonation (DS) of the copolymers was controlled with variation of ratio of SDCDPS to QBF. The copolymer structures were confirmed by FTIR spectroscopy and 1H-NMR analysis. The copolymer films obtained from N,N-dimethylacetamide (DMAc) solution showed good thermal stability, oxidative stability and mechanical properties depending upon their chemical compositions (DS from 0.2 to 0.6). Transmission electron microscopy (TEM) showed fibril like microstructures for the copolymer membranes. The copolymers showed good dimensional stability with low water uptake and swelling ratios. Ion exchange capacity (IECW) of the copolymer films was determined by NMR and titration methods. The proton conductivities of acid form membrane increased with IECW value and temperature; maximum to 88 mS/cm at 90 °C for BPAQSH-60 copolymer.