嵌段共聚物中的少数基团自组装形成高密度离子传输通道

Ion exchange membranes (IEMs) are essential components in various electrochemical systems. Ion selectivity and ion flux are the two key parameters for evaluating IEM performance, and achieving both high selectivity and high flux has long been a major challenge in both academic and industrial communities. In conventional IEMs, ionic groups assemble into a three-dimensional ion transport network. However, at low ionic group content, the formation of continuous ion channels is limited, resulting in low ion flux. Increasing the ionic group content can enhance ion flux but often leads to excessive swelling, thereby compromising selectivity. Constructing high-density ion transport channels with a minimal number of ionic groups remains a significant difficulty. To address this issue, we proposed a strategy to fabricate high-density ion channels by using tiny amounts of ionic groups. 4-Aminoazobenzene (Azo) was grafted onto a styrene-ethylene/butylene-styrene (SEBS) block copolymer containing a small amount of maleic anhydride (MA). During the grafting reaction, carboxylic acid groups were introduced in situ. Although the Azo units are grafted onto the ethylene/butylene segment, their stronger compatibility with the polystyrene (PS) domains drives their migration toward the PS regions during self-assembly. This process induces the interfacial enrichment of carboxyl groups, resulting in the formation of a high-density ion channel array. This “less-to-more” design concept differs from conventional material strategies and enables a synergistic enhancement of both ion flux and selectivity. The resulting membrane exhibited excellent osmotic energy conversion performance, achieving a power density of 9.35 W/m²under a 500-fold salinity gradient, offering a novel pathway for the development of next-generation highperformance IEMs.