Molecular Dynamics Simulation of Highly Confined Glassy Ionic Liquids

Abstract

We present a molecular dynamics simulation study of 1-octyl-3-methylimidazolium tricyanomethanide ([Omim+][TCM–]) ionic liquid capped by two silica planar surfaces. The study extends over a wide temperature range and various interwall distances. Our results indicate that the structure and dynamics of the confined system is significantly affected by the width of the film. At the shortest interwall distance of 25 A, which is comparable to the ion pair dimensions, the bulk structure is breached. The dynamics of the cation in the adsorbed layer is accelerated for the time scale of 1 ns and decelerates for longer time scales. In the most confined film, we observe a suppression of the cooperative characteristics in the diffusion. The whole phenomenon seems to be related to an Arrhenius behavior. Our proposed model suggests a stable, static liquid path in the center of the pore that facilitates the diffusion. The simulations results are consistent with a recent experimental study on the same confined system.