Thermodynamic characterization of ionic liquids

Abstract

A novel simple method is presented for the characterization of ionic liquids as regards their thermodynamic behavior in bulk phases and interfaces. For this purpose, a simple consistent thermodynamic framework has been developed which may exploit a variety of experimental information, such as activity coefficients at infinite dilution, volumetric data over a temperature/pressure range, or wetting/contact angle data over a variety of solid surfaces. This experimental information is used in order to determine LSER (Linear Solvation Energy Relationships) type molecular descriptors and surface energies that uniquely characterize each ionic liquid. The interconnection of these descriptors with the more familiar equation-of-state scaling constants is established and explored. The emerging trends in the determined molecular descriptors and the consequences and perspectives are critically discussed. As shown by a variety of examples, the efficiency and versatility of the proposed characterization method are rather promising.