Synthesis and characterization of anion-exchange membranes based on hydrogenated poly(norbornene)

Trimethylammonium-containing (TMA) polynorbornene is synthesized via ring-opening metathesis polymerization for study as an anion exchange membrane (AEM) in solid state alkaline fuel cells. The AEMs in this work are designed to incorporate flexible tethers between the TMA and polymer backbone, methyl groups at the β position, and to be semicrystalline, with the goals of high OH− conductivity, good electrochemical stability in high pH environments, and robust mechanical properties when in the membrane form. The resulting materials are found to have high conductivities, but are mechanically weak due to an overall lack of crystalline domains. Electrochemical stability appears dependent on the environment in which lifetime is measured, suggesting that the hydration state of the polymer has a substantial influence on the result.