Density, Viscosity, and Surface Tension of Synthesis Grade Imidazolium, Pyridinium, and Pyrrolidinium Based Room Temperature Ionic Liquids

Abstract

Density, viscosity, and surface tension data sets of 13 ionic liquids formed by imidazolium, pyridinium, or pyrrolidinium cations paired with dicyanamide (DCA − ), tetrafluoroborate (BF 4 − ), thiocyanate (SCN − ), methylsulfate (MeSO 4 − ), and trifluoroacetate (TFA − ) anions are reported. The properties were measured at temperatures between (293 and 363) K. The effect of the ionic liquid forming anion and cation on the physical properties is analyzed systematically. As expected, the measured density, viscosity, and surface tension of the studied ionic liquids decreased with an increment in temperature. The density measurements were linearly correlated as a function of temperature, and the viscosities were fitted to a Vogel−Fulcher−Tamman equation. The density and surface tension data were used to estimate expansivity coefficients and surface thermodynamic properties of the ionic liquids. The physical properties are determined by the nature, size, and possible interactions of the ions forming the liquid. In general, ionic liquids with dicyanamide as anion exhibited lower densities and viscosities but a somewhat higher surface tension than all other ionic liquids used here. A longer alkyl chain in imidazolium-based ionic liquids was associated with lower density, higher viscosity, and lower surface tension.