Anion exchange membranes (AEMs) have been explored for a solid ion conducting separator for various electrochemical devices such as fuel cells, electrolyzers and flow-batteries. To deliver high performance and durability of such technologies, AEMs are required to have high ionic conductivity, good chemical/alkaline stability, and good mechanical properties. Chemical/alkaline stability of the membrane can be improved by removing labile sites from the chemical structure of polymers. All-hydrocarbon polymer backbones without alkaline labile aryl ether (C_sp2–O) bonds have significantly improved chemical stability.

In this study, cyclic olefin copolymer (COC) was studied for a new class of chemically stable and low-cost polymers for AEM applications. Ethylene and norbornene are well-known inexpensive raw chemicals, and COC consists of only C–C bonds which are essential for good alkaline stability. COC was functionalized to tether the branched side chains by Friedel-Crafts bromoalkylation and converted to AEM by quaternization of the bromoalkyl groups with trimethylamine. IEC and degree of crosslinking were controlled to optimize the AEM properties. COC AEMs were prepared in both freestanding membrane and pore-filled reinforced membrane forms to study the fundamental study of the polymer material and to enhance the stability, respectively.