Effect of structural alteration of ionic liquid on their bulk and molecular level interactions with ethylene glycol

• Macroscopic and molecular level interactions of imidazolium ionic liquids in ethylene glycol have been determined.
• VmE and ΔκS are positive over the whole composition range for all investigated mixtures.
• Multiple hydrogen bonding interactions existing between unlike constituents in mixtures of varying strengths.

Mixing behavior of ionic liquids (ILs), 1-pentyl-3-methylimidazolium bromide [C5mim][Br], 1-pentyl-3-methylimidazolium tetrafluoroborate [C5mim][BF4] and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [C4mmim][BF4] with ethylene glycol has been investigated using density, ρ, speed of sound, u, and Fourier transform infrared spectroscopy (FTIR) measurements over the whole composition range at T = (288.15–318.15) K. The density values were used to calculate excess molar volumes, VmE, whereas speed of sound results have been used to calculate deviation in isentropic compressibility ΔκS. Excess properties have fitted to the Redlich–Kister polynomial equation to obtain the binary coefficients and the standard deviations. The excess properties and spectroscopic data have been analyzed in terms of effect of temperature, anion and cation of IL. The results indicates about the significance of C(2) position of the imidazolium ring in combination with the nature of anion in deciding the bulk and molecular level interactions.