Main-Chain Cobaltocenium-Containing Ionomers for Alkaline Anion-Exchange Membranes

Cationic metallopolymers representa new class of ionomersas anion-exchangemembranes (AEMs) for transporting hydroxide ions in alkaline fuelcells. In this work, main-chain cobaltocenium-containing polymerswith a complete hydrocarbon framework were synthesized by ring-openingmetathesis polymerization (ROMP) of cobaltocenium-fused cycloalkenesand cis-cyclooctene followed by backbone hydrogenation.These copolymers with varied fractions of cobaltocenium exhibit highchemical and thermal stability, low swelling, and favorable mechanicalproperties, with hydroxide conductivity as high as 95 mS/cm and about94% retention of the conductivity after 45 days of exposure to highalkaline conditions. Comparison with side-chain cobaltocenium polymer-basedAEMs reveals that the main-chain hydrocarbon-based polymers endowlower water uptake and swelling ratio while maintaining similar ionexchange capacity and hydroxide conductivity.