278323 Pure and Mixture Thermophysical Properties and Phase Behavior of Lipidic Ionic Liquids
Recently, our group described the synthesis and solid/liquid equilibrium of lipidic ionic liquids: ionic liquids with long alkyl chains (C16-C20) that, like natural lipids, contain cis-unstaurations which dramatically lower their melting points relative to their saturated analogs. These compounds are of interest for a number of applications including reactions and separations involving non-polar compounds, models for biological membranes, separation of naturally occurring lipids from biological media and advanced lubricants. The first generation of these compounds utilized cis-double bonds to impart asymmetry in the alkyl chain. While effective at lowering melting points, the unsaturations create sites for oxidative degradation, much like rancidity in natural oils. Subsequently, we have developed other strategies to impart asymmetry in the alkyl chain including mid-chain branching and the inclusion of heteroatoms in the alkyl chain. Thioether groups, introduced through thiol-ene “click chemistry,” have been a particularly valuable as they are synthetically very accessible and allows for a large degree of structural tunability as the position of the sulfur group in the chain is varied.
For these compounds to be useful in the potential applications mentioned above, the physical properties and phase behavior of these compounds must be explored. Additionally, property trends throughout the different subclasses must be described to identify where specific species may be employed and where expanded synthetic strategies would be beneficial. We are currently working to characterize these ionic liquids as pure species and as mixtures with other ionic liquids and with molecular species. This work will present our results relating to the pure and multicomponent thermophysical properties and phase equilibria of these systems.