Synthesis of proton conductive polymers with high electrochemical selectivity

Electrochemical selectivity achieved in the cross-linked polymer membrane based on chain-end-functionalized fluoropolymers containing perfluorosulfonic acid side chains was reported. The copolymer of vinylidene fluoride (VDF) and perfluoro(4-methyl-3,6-dioxane-7-ene) sulfonyl fluoride (PFSVE) was prepared through a radical polymerization using 4-tert-butoxycarbonylaminobenzoyl peroxide as the initiator. The removal of the protecting tert-butoxycarbonyl groups in the copolymer using iodotrimethylsilane yielded the copolymer terminated with amino groups. The Hydrolysis of the sulfonyl fluoride groups to the ammonium salt was achieved in triethylamine methanol or water solution, and the sulfonic acid form of the polymer was obtained by ion-exchange with HCI aqueous solution. The cross-linked membrane exhibited methanol permeability of 1.89 × 10^-9cm²/s, which was over 2 orders of magnitude lower than Nafion 117 with a methanol permeability of 1.92 × 10^-6 cm²/s.