The physicochemical properties of selected imidazolium chloride ionic liquids in tetraethylene glycol: Experimental and computational approach

Abstract

In this work, the influence of the side chain length of five ionic liquids (ILs) containing N3-substituted 1-methylimidazolium chloride ionic liquids, [Cnmim][Cl] (n = 0, 1, 2, 4, 6) on the interactions with tetraethylene glycol (TEG) was studied. Measuring the density and electrical conductivity of the IL + TEG mixtures in the temperature range (278.15–313.15) K, the values of physicochemical properties, such as apparent molar volume, apparent molar volume at infinite dilution, Masson’s interaction coefficient, limiting apparent molar expansibilities, Heppler’s coefficient, ion association constants, thermodynamic parameters of ion-pair formation, as well as diffusion coefficient were calculated. The results obtained from these experiments were supported by molecular dynamics (MD) simulations. In comparation with systems containing ethylene–glycol (IL + EG), the calculated free volumes in TEG are about three times higher than in EG. Therefore, assuming that the packing effect is responsible for the lower apparent molar volume at infinite dilution, values in the TEG seem reasonable. The values of ion association constants in TEG are lower than in EG. The ion association process is spontaneous for all investigated ILs in TEG solutions and entropy-driven.