Temperature dependent study of thermophysical and optical properties of binary mixtures of imidazolium based ionic liquids

Abstract

The experimental values of densities (r) and speeds of sound (u) of the binary mixtures of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF₄] with α,ω-propanediols have been used to calculate the internal pressure (), free volume (V_f), excess internal pressure (), excess free volume (), excess free energy (), excess enthalpy () and excess entropy () covering the entire composition range expressed by mole fractions of ionic liquid at temperatures (298.15, 303.15, 308.15, 313,15, 318.15 and 323.15 K). The refractive indices (n_D) of these mixtures have been measured at above-mentioned temperatures and the deviations in refractive index () have been calculated. The results have been interpreted in terms of intermolecular interactions between the component molecules in the mixture. The variations of these excess properties with composition indicate that the interactions between [Bmim][BF₄] and α,ω-propanediols in these mixtures follows the order: 1,2-propanediol > 1,3-propanediol.