(705d) Using Monte Carlo Simulations to Study the Interfacial Behavior of Ionic Liquids (Invited Talk)

Ionic liquids show interesting thermo-physical properties due to their unique chemical nature, which is characterized by comparative strengths of Coulombic and dispersion interactions. In this presentation, we discuss the wetting properties of ionic liquids. We provide results for two model systems: (1) Lennard-Jones ions and (2) realistic models for room temperature ionic liquids.  Interfacial properties are computed using a free energy based approach that involves performing Monte Carlo simulations to grow a liquid or vapor film on the solid surface of interest. Expanded ensemble simulations are used to scan a broad range of temperatures and substrate strengths, which enables us to study systems in different wetting regimes. Our results indicate that one can tune the temperature response of the contact angle by varying the strength of the Coulombic interaction relative to the dispersion interaction. More specifically, as one increases the relative strength of the Coulombic interaction, the range of surface conditions over which the contact angle decreases with increasing temperature is reduced. We discuss how one can link these observations to the solid-fluid and liquid-vapor surface excess entropies. We also examine the nanoscale structure of the solid-fluid and liquid-vapor interfaces.