Physical properties of binary mixtures : ionic liquids + alcohols

Abstract

Information on the interactions between ionic liquids and molecular solvents are essential for the understanding of the function of ionic liquids in related procedures, and excess properties are sensitive probe for studying these interactions. In this paper, physical properties such as densities and speeds of sound of the binary systems containing 1–propyl–4 methylpyridiniumbis(trifluoromethylsulfonil)imide and 1propyl–4–methylpyridiniumbis(trifluoromethylsulfonil)imide, ethanol and propanol, over the whole composition range were measured at T=(298.15, 308.15, 318.15) K and at atmospheric. These data were used to calculate the corresponding derived properties such as excess molar volumes and excess molar isentropic compressions, which were fitted with the Redlich-Kister equation. For the studied systems, the excess molar volume values show a sinusoidal behaviour with a minimum at high concentrations of alcohol due to changes from negative to positive values when the alcohol´s alkyl chain length increases. The excess molar isentropic compression values are negative over the whole composition range and presenting also a minimum at high concentrations of alcohol. It is possible observed that an increase of the temperature causes that the negative excess molar volume and excess molar isentropic compression values for the alcoholic mixtures deviate more from ideality.