Non-covalently crosslinked anion exchange membranes: Effect of urea hydrogen-bonding group position

To investigate the effects of noncovalent intermolecular interaction on the performance of anion exchange membranes (AEMs), two types of side chain urea-containing poly(phenylene oxide)-based AEMs, namely, benzyl urea-linkaged terminal quaternary ammonium (QA)-containing AEMs (bU-AEMs) and benzyl QA-linkaged urea-containing AEMs (sU-AEMs), were synthesized and comparatively studied. The analyses by solubility test and variable-temperature infrared spectroscopy showed that the urea-based hydrogen-bonding strength in bU-AEMs was higher than that of sU-AEMs. The bU-AEMs were characterized with a stable water uptake (WU), as well as high swelling resistance relative to that of the sU-AEM counterparts, as the temperature increases. A high chloride conductivity of 50.3 mS cm −1 was achieved for bU-AEM-0.45 at 90 °C, while its WU maintained a moderate value (80.6 wt%). The H 2 -O 2 single fuel cell performance using the bU-AEM-0.35 membrane as a separator reached a peak power density of 68 mW cm −2 , which was higher than that of the sU-AEM-0.35 sample with 48 mW cm −2 . More importantly, there was less than 10% conductivity loss for the bU-AEMs after incubation in 1 M NaOH at 60 °C after 7 days, while approximately 30% loss was observed for the sU-AEMs. The results indicated that the hydrogen-bonding crosslinking strategy, as well as the configuration of H-bonding groups, provides a platform to tune the properties of AEMs suitable for fuel cell applications .