Thermophysical properties of binary mixtures {1-methyl-3-pentylimidazolium tetrafluoroborate + polyethylene glycol methyl ether}

Few reports are available on the thermophysical properties of ionic liquid (IL) and the polymeric (or oligomeric) solution binary system. In this study, the densities, viscosities, and refractive indices were determined for IL mixtures formed by 1-methyl-3-pentylimidazolium tetrafluoroborate [MPI][BF4] with polyethylene glycol methyl ether (MPEG) [Mw = 350] over the mole fraction ranging from 0.1 to 0.9 and temperatures from 293.15 to 353.15 K at intervals of 5 K and atmospheric pressure. The temperature dependence of density and dynamic viscosity for both neat [MPI][BF4] and its binary mixtures were described by an empirical linear equation and by the Vogel–Tammann–Fulcher (VTF) equation, respectively. Excess molar volumes, viscosity deviations, and refractive index deviations were calculated from the experimental data and fitted to a Redlich–Kister polynomial function. The excess molar volume and viscosity deviations for the binary system were negative over both the composition and temperature ranges, whereas the refractive index deviations were always positive. The results have been interpreted in terms of ion–dipole interactions and the structural factors of the IL and MPEG molecular liquids.

► Thermophysical properties of the {ionic liquid + polymeric solution} binary system are elaborated.
► The temperature dependence of dynamic viscosity for neat ionic liquid and its binary mixtures is described by the Vogel–Tammann–Fulcher (VTF) equation.
► Redlich–Kister type of polynomial equation is used to correlate the excess molar volumes, viscosity deviations, and refractive index deviations.
► Ion–dipole interactions and structural factors of the ionic liquid and polyethylene glycol methyl ether are reported.