Ion Transport in Nanostructured Block Copolymer Membranes for Ion-Selective Separations

Ion-selective polymer membranes are of great interest in various applications related to polymer electrolytes in batteries, resource recovery, and critical element extraction. To understand the origin of ion-selectivity in polymer membranes, specifically for Li-separation, we have designed a systematic library of nanostructured block copolymer membranes based on polyisoprene-b-poly(ethylene oxide) (PI-PEO-PI) triblock copolymer. A series of PI-PEO-PI -based polymer membranes were successfully prepared with varied crosslinking density. We systematically evaluated the structural (via 1H-NMR), thermal (via TGA and DSC) and ion/water transport properties in the polymer membranes. Transport properties of interested ions and water were characterized via measuring ion/water solubility, diffusivity and permeability in relevant feed conditions. This model system enables us to elucidate the mechanism of ion-selectivity in polymer membranes and thus help us to design next-generation ion-selective membranes.