(83a) Using Molecular Simulation to Understand the Interfacial Behavior of Ionic Liquids

Understanding the bulk and interfacial properties of ionic fluids is important for several industrial applications. In this presentation, we examine the properties of a relatively simple ionic system consisting of the restricted primitive model (RPM) at a structureless substrate that interacts with the fluid via an attractive van der Waals potential of variable strength. The model system exhibits several behaviors that are distinct from simple non-ionic fluids (e.g., Lennard Jonesium) at an equivalent structureless substrate. For example, the contact angle of the RPM system increases with increasing temperature over a relatively wide range of substrate strengths. In contrast, the contact angle of a non-ionic fluid generally decreases with increasing temperature. One of the consequences of this behavior is that the RPM system generally does not tend towards a wetting point with decreasing temperature. There are also interesting ramifications regarding the transition from the partial wetting to prewetting, to complete wetting regimes. We discuss now these trends are related to the microstructure of the fluid at the liquid-vapor and solid-liquid interfaces. The interface potential approach is used to quantitatively explore the interfacial properties of the RPM system, with interface potentials generated via Monte Carlo simulation.