Using Monte Carlo Simulations to Study Wetting Behavior of Ionic Liquids

Room temperature ionic liquids (RTILs) are finding applications in many emerging technologies due to their low vapor pressures, high conductivities and excellent solvent capabilities. Understanding the wetting behavior of ionic liquids is crucial for developing these technologies. This presentation focuses on our efforts to use Monte Carlo simulations to study the wetting behavior of simplest models of ionic liquids comprising of spherical cations and anions. Our approach is to study the wetting behavior of ionic fluids with increasing strengths of electrostatic interactions relative to dispersion interactions. The ranges of relative ionic strengths that we investigate are those observed in RTILs and molten alkali halides. The coexistence curve for each of these fluids is generated using grand canonical temperature expanded ensemble simulations. The surface tension and the contact angle for a given substrate are calculated from interfacial simulations using a free energy based method developed by our group. The variation of these quantities with substrate strength and temperature is studied using expanded ensemble simulations. Results are presented to show the dependence of contact angle on temperature and substrate strength for fluids with different strengths of coulombic interactions compared to dispersion interactions. We have also examined the temperature dependence of surface tension for each of these fluids. In the future we plan to apply the above techniques to study the wetting behavior of RTILs using more realistic models.