Physicochemical and excess properties of binary system mixtures of ether-functionalized ionic liquids with DMSO

•[COC4mim][Gly], [COC4mim][Ala] and [COC4mim][Thr] were prepared.•The physicochemical properties of all binary mixtures were measured.•The correlation between VE (or gsE or ΔG≠r) and x1 was investigated.•The predicted surface tensions of ILs + DMSO binary mixtures were obtained.•The activation properties for viscous flow of binary mixture were studied. In the full molar fraction range, the density, surface tension and viscosity of 1-(4-methoxybutyl)-3-methylimidazolium glycine ([COC4mim][Gly]), 1-(4-methoxybutyl)-3-methylimidazolium alanine ([COC4mim][Ala]) and 1-(4-methoxybutyl)-3-methylimidazolium threonine ([COC4mim][Thr]) with DMSO binary mixtures were determined. The variation trends of excess molar volume (VE), excess molar surface Gibbs energy (gsE), Gibbs energy of activation for viscous flow of the relative viscosity (ΔG≠r) and x1 of binary system mixture were systematically studied, and the interaction between ether-functionalized ionic liquids (ILs) and solvent molecules in binary system mixtures was studied. According to the molar surface Gibbs energy definition, excess molar surface Gibbs energy definition and Redlich-Kister empirical equation, the correlation between the predicted and experimental surface tension values of ILs + DMSO binary system mixtures was investigated. Furthermore, using the improved Eötvös empirical equation and thermodynamic formula, molar surface entropy and molar surface enthalpy of binary system mixture were calculated. The molar surface enthalpy of binary mixture was independent of temperature. This fact indicated that the process from the bulk to the surface of binary system mixture was an isocoulombic reaction.