Effect of steric constraints on the physico-electrochemical properties of sulfonated polyaromatic copolymers

The impact of incorporating additional steric restrictions into highly sterically encumbered sulfonated polyaromatic polymers was investigated. Copolymers possessing between 0 and 10% nonlinearorthoormetabiphenyl units in an otherwise linearparabiphenyl-containing sulfo-phenylated poly(phenylene) were synthesized in yields >80% and evaluated on the basis of their physical and electrochemical properties. When incorporated into sulfonated copolymers in <= 5 mol%,orthoandmetalinked biphenyl moieties reduced membrane swelling in water by up to 23 and 19 vol%, respectively, compared to strictlyparabiphenyl-linked copolymers. Despite this, copolymers possessing nonlinear, biphenyl-linked monomers displayed a decrease in proton conductivity and mechanical strength. This study reinforces the importance of considering restricted rotation, backbone flexibility, and chain entanglement in the design of polymers aimed at improving their physical and electrochemical properties. (c) 2020 Society of Industrial Chemistry

Automated summary

The study demonstrates that incorporating additional steric restrictions into highly sterically encumbered sulfonated polyaromatic polymers can reduce membrane swelling, but also decrease proton conductivity and mechanical strength.