Exploring the Potential of Triphenylmethane-Based Polymers Prepared via Facile Friedel–Craft (F–C) Hydroxyalkylation Polymerization as Gas Separation Membranes: Effect of Substituent Group

This work reports a versatile polymer platform that produces high molecular weight polymers containing triphenylmethane-based backbones with highly tailorable chemical structures via facile Friedel–Crafts (F–C) hydroxyalkylation polymerization and investigates their applications as gas separation membrane materials. Two series of triphenylmethane-based polymers with systematically varied substituent groups were synthesized from carefully selected monomers containing varying substituent groups. Chemical structures, thermal properties, and microstructures were comprehensively characterized. The separation performance of the polymer membranes was evaluated via conducting pure-gas permeation measurements to elucidate how substituent groups influence the fundamental gas transport properties. Variations of side groups display dominant effects on gas diffusion processes in which bulky groups disrupt chain packing more efficiently, while steric hindrance and overall flexibility of segments also play a role, leading to diverse and highly tailorable separation performance. Some membranes in this work exhibit much-enhanced permeability and selectivity comparable to those of commercial materials. The feasible and flexible synthesis procedure as well as promising separation performance indicate the great potential of triphenylmethane-based polymers for major light–gas separations.