High-temperature-operable poly(phenylene)-based multiblock copolymer membrane for anion exchange membrane electrochemical energy devices

A thermally stable anion exchange membrane (AEM) based on quaternized multiblock poly(phenylene-co-arylene ether)s (QPPs) has been developed. Incorporation of benzophenone side chains into the hydrophilic phenylene segments improves the solubility of the rigid phenylene polymer and enhances phase separation. The QPPs demonstrate high ion conductivity, reaching 0.15 S cm –1 at 90% relative humidity (RH), and maintain 67% of their conductivity over 30 h at 70 °C and 50% RH. Remarkably, the fuel cell performance of B-QAA-1.8 matches that of the commercial FAA-3-50. In water electrolysis tests, the B-QAA-1.8 membrane demonstrates unprecedented thermal stability and performance at 90 °C, maintaining its structural integrity and showing minimal performance degradation. Such high-temperature durability for AEMs in water electrolysis has rarely been reported. These results indicate that phenylene-based block copolymer AEMs have significant commercial potential in both AEM fuel cells and water electrolysis. • Multi-block copolymers containing hydrophilic segments as a phenylene block were synthesized. • The block copolymers (B-QAAs) showed a well-developed hydrophilic/hydrophobic morphology compared to its random form. • A high hydroxide conductivity of 0.151 S cm-1 was obtained for the B-QAA-1.8 membrane at 90 %RH and 70 °C. • The well-developed morphology also affected better stability, not only higher conductivity. • The B-QAA-1.8 showed better performance than commercial FAA-3-50 in AEMFC and AEMWE.