Interplay of backbone rigidity and water content on ion/ion selectivity in hydrated polymer membranes*

Increasing lithium demand requires new and improved methods for purification. Membrane-based separation processes, such as selective electrodialysis, hold promise for efficiently separating lithium from other contaminants, such as magnesium. Successful implementation of these technologies requires materials with high selectivity of lithium over other ions while maintaining high lithium conductivity. Two factors that are known to play important roles in governing membrane performance are equilibrium water content and polymer segmental dynamics. We perform coarse-grained molecular dynamics simulations to examine the interplay between these two factors and the impact on ion/ion selectivity. These simulations rationalize our observed experimental selectivity trends for cellulose acetate membranes and provide guidance for future investigation into improved membrane design.