(376r) Transport Mechanisms of Polar Solutes in a Cross-Linked Hii Phase Lyotropic Liquid Crystal Membrane

Cross-linked inverted hexagonal phase lyotropic liquid crystal (LLC) membranes possess pores of uniform size with a complex chemical topology that make them promising for selective separations. We characterized transport of water, sodium ions and 20 small polar solutes within the pores of an LLC membrane using atomistic molecular simulations. Due to the inhomogeneous pore compostion, we observed radially dependent transport mechanisms that are a strong function of solute chemical functionality. In general, all solutes perform intermittent hops between lengthy periods of entrapment. Three different trapping mechanisms are responsible for this behavior. First, solutes that drift out of the pore can become entangled among the dense monomer tails. Second, solutes can donate hydrogen bonds to the monomer head groups. Third, solutes can coordinate with sodium counter ions. The degree to which a solute is affected by each mechanism is dependent on the chemical functionality of the solute. We have used our detailed mechanistic understanding in order to construct a stochastic model which we can use to project the long term behavior of the solutes and ultimately predict selectivity. Using the insights developed in this study, we can begin to think about how to redesign existing LLC membranes in order to perform solute-specific separations.