Partially fluorinated poly(arylene ether)s bearing long alkyl sulfonate side chains for stable and highly conductive proton exchange membranes

• Published in: Journal of membrane science Vol. 549; pp. 12 - 22
• Main Authors: Chen, Xialin, Lü, Haixia, Lin, Qilang, Zhang, Xiang, Chen, Dongyang, Zheng, Yuying
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2018
• Subjects: Condensation polymerization; Fluorinated ionomers; Phase separation; Thiol-ene reaction; Fluorinated ionomers; Condensation polymerization; Thiol-ene reaction; Phase separation
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2017.11.066

Condensation polymerization of two diallyl-containing bisphenol monomers with decafluorobiphenyl catalyzed by CsF at low temperatures yielded quantitatively the diallyl-containing fluorinated poly(arylene ether)s, which after the thiol-ene click reaction with sodium 3-mercapto-1-propanesulfonate yielded sulfonated fluorinated poly(arylene ether)s (SFPAEs) with long alkyl sulfonate side-chains. The sulfonate groups were spaced by 7 atoms away from the aromatic backbone, in stark contrast to the previous reports where only 6 spacing atoms could be achieved using a similar chemistry but rather harsh reaction conditions. Two series of SFPAEs based on bisphenol A and bisphenol S units, respectively, were both found to exhibit distinct phase separation and enhanced proton conductivity. Specifically, the SFPAE-A-70 with an ion exchange capacity (IEC) of 1.62mmolg−1 exhibited an in-plane proton conductivity of 90mScm−1 at room temperature, which was slightly higher than that of Nafion 212. Furthermore, all of the SFPAEs showed significantly improved oxidative stability in Fenton's reagent when comparing to non-fluorinated analogs. This study offered a new strategy for the synthesis of highly branched ionomers with long and flexible aliphatic side-chains for high performance PEMs. •Long alkyl sulfonate side chains were incorporated by a new synthetic route.•Distinct phase separations were observed by TEM and SAXS characterizations.•Similar proton conductivity to Nafion 212 was achieved at IECs of ~ 1.60mmolg−1.•Excellent oxidative stabilities were observed because of the content of F atoms.•Improved efficiencies in vanadium redox flow batteries were demonstrated.