Volumetric behaviour of 1-Butyl-3-Methyl imidazolium hexafluorophosphate with ethylene glycol derivatives: Application of Prigogine-Flory-Patterson theory

Physical properties, such as densities, ρ, and refractive indices, n, for the binary mixtures of 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] with ethylene glycol derivatives: diethylene glycol monomethyl ether (DEGMME); triethylene glycol monomethyl ether (TEGMME); triethylene glycol dimethyl ether (TEGDME); and tetraethylene glycol dimethyl ether (TetEGDME) have been measured over the whole composition range. Experimental densities were used to estimate excess molar volumes, VmE, apparent molar volumes, Vϕ,i, partial molar volumes, V̅m,i, excess partial molar volumes, V̅m,iE, and their limiting values at infinite dilution, Vϕ,i∞, V̅m,i∞, and V̅m,iE,∞ respectively. Volumetric results have been analyzed in the light of Prigogine-Flory-Patterson (PFP) statistical mechanical theory. Interaction parameters have been calculated from VmE values for all the studied systems. The solute-solvent interactions have been investigated in terms of each of the three contributions viz. interactional, free volume and P⁎ obtained from PFP theory at equimolar concentration. Deviations in refractive indices, Δϕn have been calculated from experimental measurements of refractive indices. Excess properties are fitted to the Redlich-Kister polynomial equation to obtain the binary coefficients and the standard errors.