Gating Ionic Transport with Chiral Solvent at a Polar Interface

The electrochemical properties that are important for membranes used for sensing technologies, ionic separations and energy-storage devices are sensitive to the arrangement of ions and solvent molecules at solid interfaces, often described by the electrical double layer model for aqueous solutions. However, this model does not hold for systems that exhibit spatial organization, such as polar, aprotic solvents. This work investigates how the solvent structure of propylene carbonate (PC) dictates ion and fluid transport at polar interfaces. We evaluate the analogy of solvent interfacial organization to lipid-bilayers, by investigating the existence of a membrane dipole potential and how it dictates ion partitioning. PC is also a chiral solvent and therefore exists in its enantiomerically pure and racemic forms. Electrokinetic measurements of ionic transport reveal that the effective surface potential significantly differs between LiClO₄ solutions prepared using enantiomerically pure and racemic PC. The origin of the chirality-dependent organization is discussed and attributed to the racemic form creating a highly organized layered structure compared to the enantiomerically pure form, which dictates the favorable position for cations and anions in each case. The results highlight the importance of solvent molecular organization on interfacial potential and point to the potential for tuning ionic and fluidic transport with solvent chirality.