The term “ionic liquid” (IL) has been coined to describe an interesting class of fluids that are comprised of fully dissociated ions yet are liquid near ambient conditions. The prototypical IL is made up of a relatively simple anion and a bulky organic cation with various substituent groups. The anion, cation, or substituent groups can be changed to produce an almost infinite variety of compounds with radically different properties. The water-stable class of ionic liquids of interest to us has only been known for about ten years. These ILs are typically comprised of imidazolium, ammonium or pyridinium cations having alkyl groups in the C2 to C8 range. Anions are usually an inorganic species such as [BF4]- , [NO3]- or CF3SO2-. These ILs have many properties that make them interesting to study from both a practical and theoretical standpoint: they are completely non-volatile (and hence “greener” than traditional organic solvents), have an unusually large liquidus range of 200-300 oC and dissolve both polar and non-polar species. Potential applications of ILs include solvents for homogeneous catalysis, high temperature lubricants, separations media, electrolytes for fuel cells, heat transfer fluids, and rocket propellants.

In this presentation we report our latest results on the characterization and application of a range of different ILs. We present basic experimental data on pressure-volume-temperature thermodynamic properties as well as vapor-liquid equilibrium data for a range of gases and water with different ILs. We also discuss ecotoxicity studies that indicate these liquids may not be as “green” as originally touted. Using a mix of quantum chemistry and experimental benchmarks, we have developed classical intermolecular potentials for the ILs and successfully computed their thermodynamic and transport properties using classical Monte Carlo and molecular dynamics simulations. We discuss how the simulations have shed light on detailed aspects of the structure of different ILs, and are helping guide synthetic efforts at tailoring the properties of new ILs.