Thermophysical Properties of Imidazolium-Based Lipidic Ionic Liquids

The thermophysical properties of three lipidic ionic liquids, 1-oleyl-3-methylimidazolium bistriflimide, 1-elaidyl-3-methylimidazolium bistriflimide, and 1-linoleyl-3-methyl-imidazolium bistriflimide are measured at 1 bar as a function of temperature over the range of 273 K to 353 K and correlated to appropriate models. Each of these compounds is a variation on 1-C-18-3-methylimidazolium bistriflimide, where the C-18 chain contains one or more unsaturations, incorporated into the structure to lower the melting point. Derived properties such as molar volume and volume expansivity are also calculated. The data are compared with literature values for shorter chain 1-n-alkyl-3-methylimidazolium bistriflimide salts. The longer chains impart lower densities and higher viscosities relative to their shorter chain homologues. Although the subtle structural differences between the three compounds result in significant differences in melting points, there is less of an effect on the liquid phase thermophysical properties.