Poly(bibenzyl-trifluoromethyl piperidinium)-Based Anion Exchange Membranes with High Alkaline Durability

High alkaline stability and hydroxide conductivity are critical parameters when designing polymeric anion exchange membranes (AEMs) for alkaline electrochemical energy devices. Here, a series of aliphatic chain-containing poly(bibenzyl-trifluoromethyl piperidinium) copolymers were synthesized via superacid-catalyzed polycondensation and subsequent Menshutkin quaternization reactions. Introducing 1,1,1-trifluoroacetone into the polymer backbone improves the trade-off between hydroxide conductivity and dimensional and alkaline stability. The synthesized AEMs based on poly(bibenzyl-trifluoromethyl piperidinium) copolymers possess high conductivity (up to 170 mS cm–1), high alkaline stability (<5.5% loss in hydroxide conductivity), mechanical robustness (tensile strength (TS) > 50 MPa, elongation at break (Eb) up to 25%), and excellent dimensional stability. All of these properties are attributed to the combination of piperidinium cation and rigid high-molecular-weight aryl ether-free backbone.