Developing a Molecularly Detailed Theoretical Framework for Predicting the Thermodynamic Properties of Ionic Liquids

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Abstract#1067642McCabe, Clare M.Vanderbilt UniversityIonic liquids (ILs) are liquids, comprised entirely of complex ions, that typically have melting points at or below room temperature, distinguishing them from high temperature molten salts (e.g., NaCl). The cations and anions each impart different physical and chemical properties to the IL enabling ILs to be tailored to provide desired properties. While initial interest in ILs focused on their use as solvents, it has since broadened dramatically with ILs finding applications from catalysis, separations, sensors, solar cells, batteries, thermal fluids and lubricants. These applications, combined with the number of possible ILs being estimated to be in the billions, underlines the need to develop an accurate tool to design task-specific ILs.Despite increased experimental studies and physical property investigations, it is currently not possible to predict which ion combinations will lead to a desired set of properties. The limited progress to date in IL design has been achieved primarily through experimentation in chemical composition leading to empirical heuristics relating chemistry to properties.Despite its obvious utility, a predictive design methodology for ILs, based upon a deep physical understanding of the structure and interactions within ILs, does not exist today. This is in part because ILs and their mixtures with other molecular species are exceptionally complex systems and present particularly difficult molecular modeling challenges, both from simulation and theory points of view, especially if we wish to be able to predict IL properties in the absence of experimental data. We will address this need through the development of a molecular-based theoretical framework with which to study the thermodynamic properties of ILs. The approach developed will be akin to the models used in molecular simulation studies and will enable the prediction of IL properties from the chemical composition, so eliminating empiricism in estimating the properties of a given combination of ions and their mixtures with molecular species. In addition to enabling product design for ILs and their mixtures, the proposed methodology will be a crucial component in the design of chemical processes involving ILs.