Structure and Dynamics of an Ionic Liquid Mixture Film Confined by Mica

In a recent article ( J. Phys. Chem. C 2019, 123, 4914−4925) we studied using molecular dynamics simulations the structure of an ionic liquid (IL) mixture comprised of 1-methyl-3-octylimidazolium octylsulfate and 1-ethyl-3-methylimidazolium ethylsulfate confined by vacuum interfaces. At these interfaces, the mixture formed an apolar blocking layer concealing the smaller and more polar ions to the interior of the liquid phase. In the current work, and for the same IL mixture, we study the case of confinement between (001) mica surfaces, where the solid provides a flat and polar ionic interface. Our focus is twofold; first, we want to understand the structural and dynamical behaviors of the IL mixture at the boundary where the confining interface is highly polar, and second we want to establish how far away from the interface liquid behavior is recovered. This last point is particularly important in light of puzzling recent experimental results regarding the behavior of ILs and solutes dissolved in them und...