Comb-shaped cardo poly(arylene ether nitrile sulfone) anion exchange membranes: significant impact of nitrile group content on morphology and properties

Abstract

A series of comb-shaped cardo poly(arylene ether nitrile sulfone) (CCPENS-x) materials were synthesized by varying the content of nitrile groups as anion exchange membranes (AEMs). The well-designed architecture of cardo-based main chains and comb-shaped C10 long alkyl side chains bearing imidazolium groups was responsible for the clear microphase-separated morphologies, as confirmed by atomic force microscopy. The ion exchange capacity (IEC) of the AEMs ranged from 1.56 to 1.65 meq. g⁻¹. With strong dipole interchain interactions, the effects of nitrile groups on the membrane morphology and properties were investigated. With the nitrile group content increasing from CCPENS-0.2 to CCPENS-0.8, CCPENS-x revealed larger and more interconnected ionic domains to form more efficient ion-transport channels, thus increasing the corresponding ionic conductivity from 25.8 to 39.5 mS cm⁻¹ at 30 °C and 58.6 to 83 mS cm⁻¹ at 80 °C. Furthermore, CCPENS-x with a higher content of nitrile groups also exhibited lower water uptake (WU) and swelling ratio (SR), and better mechanical properties and thermal stability. This work presents a promising strategy for enhancing the performance of AEMs.