Opening Doors to Future Electrochemical Energy Devices: The Anion-Conducting Polyketone Polyelectrolytes

The numerous potential benefits of incorporating anion-exchange membranes (AEMs), in place of proton-exchange membranes (PEMs), in energy storage and conversion technologies renders their development of fundamental importance for the continued evolution of alternative energy systems. However, the widespread implementation of AEMs is currently plagued by a range of problems including lower conductivity (with respect to PEMs), poor stability, and high cost. This study reports the conversion of polyketone, one of the world's most mass produced and cheap polymers, to a new highly tuneable polymer architecture, functionalized polyketone (FPK), that demonstrates a range of excellent properties rendering it a significant prospect for AEM materials. The thermal, processing, and ion-conducting properties of FPK are governed by the amount and nature of the newly formed N-substituted pyrrole pendant side groups. At 80 °C, the quarternized pyridyl FPK derivative (4MPyrFPK) yields ion-conductivities of 8.6 and 10.5 mS cm-1 in the iodide and hydroxide forms. In addition, the hydroxide form of 4MPyr-FPK demonstrates remarkable stability toward the typically problematic alkaline conditions. No chemical decomposition is observed to the membrane after imbibing it in KOH solution for 72 h, and furthermore, the ion-conductivity is demonstrated to remain constant for at least 30 d at 80 °C.