Bifunctional side-chains decorating a distorted poly(aryl ether sulfone) backbone to endow an anion exchange membrane with high perm-selectivity for chloride ions

Mono-valent selective ion-exchange membrane, as the core component of selective electrodialysis (SED), has received extensive attention. In this work, we report a mono-valent selective anion-exchange membrane (AEM), which was fabricated with distorted poly(aryl ether sulfone) and decorated with bifunctional side-chains providing anion exchange groups and hydrophobic segments. By tuning the length of the hydrophobic side-chains, the nanophase separation within AEMs was finely tuned, evidenced by an ionic cluster size of about 0.47 nm from SAXS analysis. The optimized AEM (PAES-TA-7 AEM) shows a very low water swelling ratio of 6.4%, signaling good dimensional stability. The perm-selectivity () of PAES-TA-7 AEM during ED reached 107 at 2.5 mA∙cm−2 (ion flux: 2.69 × 10−8 mol·cm−2·s−1 at 90 min) significantly exceeding that of the commercial Neosepta ACS (11; 2.08 × 10−8 mol·cm−2·s−1). It is inferred that the ion channels, resulting from nanophase separation between the side-chains and the backbone, as well as the free volume cavity created by the distorted backbone, significantly contribute to the smooth transport of the Cl– ions through the AEM with less resistance. As a result, it is believed that this work offers a useful strategy to advance the monovalent anion-selective membranes.