Enhanced Fuel Cell Performance with Robust Pyridinium-Derivative-Functionalized SBS Triblock Copolymer Anion-Exchange Membranes

A series of polystyrene-<i>block</i>-polybutadiene-<i>block</i>-polystyrene (SBS) membranes functionalized with pyridinium derivatives (SBS-QA⁺py) were synthesized through free-radical chlorination of the polybutadiene segments using azobis(isobutyronitrile) (AIBN) as the free-radical initiator, promoting uniform chain growth. The resulting SBS-QA⁺py anion-exchange membranes (AEMs) were quaternized via a conventional solution-casting method. The membranes exhibited controlled ion-exchange capacities (IECs), water uptake (WU), and optimized interionic separation, achieving a balance between hydration, dimensional stability, and mechanical integrity. Noncovalent stacking interactions between the polystyrene and pyridinic segments significantly contributed to these properties. Notably, the SBS-Qdpy₂ AEM achieved a peak ionic conductivity of 101.23 mS cm^-1 at 80 °C (IEC: 1.72 mequiv g^-1) and a peak power density of 398.14 mW cm^-2 in a H₂/O₂ flow single cell at 80 °C, surpassing the performance of previously reported SBS-based AEMs. The membranes also demonstrated excellent chemical durability in 1 M NaOH solutions over 30 days, highlighting superior alkaline stability. These results underscore the critical role of optimized ion exchange and membrane morphology enhancing the fuel cell performance, positioning SBS-QA⁺py AEMs as promising candidates for next-generation fuel cells. Optimizing grafting, quaternization, and cross-linking will create stable AEMs with selective, well-defined nanoionic channels for efficient anion diffusion.