Density, surface tension and glass transition temperature of series of mono-, di-, and tri-cationic imidazolium-based ionic liquids-A predictive approach

Abstract

To respond to the problems in experimental studies on the massive number of possible ionic liquids (ILs), the chemists and engineers try to develop the predictive models for different thermophysical properties of these compounds from the knowledge of their structures. In spite of monocationic ionic liquids (MILs), the available experimental data for multicationic ILs are scarce and often contradictory. In this work, simple group contribution methods (GCMs) were developed to estimate the density, surface tension and glass transition temperature of series of mono-, di-, and tri-cationic imidazolium-based ILs at ambient conditions. The studied ILs contain different anions and the number of carbon atoms in the alkyl chain of their cations vary from 2 to 12. The contribution of each of the structural groups in density and surface tension has been estimated based on the MILs with the lowest chain length i.e. MIL containing [C2mim]+ and also methyl and methylene groups based on the additivity of molar volumes and parachors. For glass transition temperature, the contributions proposed by Lazzus et al. for MILs (Thermochim. Acta 528 (2012) 38–44) were used. The results have been compared with the literature values where they exist. The proposed GCMs are easy to use and can extend to different mono- and multi-cationic ILs. Also, they can provide predictions of the property values for ILs which were never studied previously. The results showed that the method is successful in its predictions. The absolute average deviation, AAD%, for the density, surface tension and glass transition temperature of MILs are 0.31%, 2.48% and 0.56%, respectively. AAD% values of these properties for DILs are 0.71%, 5.37% and 3.07%, respectively.