Comparative Study of Influence of Ethanol and 2,2,2-Trifluoroethanol on Thermophysical Properties of 1-Ethyl-3-methylimidazolium Dicyanamide in Binary Mixtures: Experimental and MD Simulations

Abstract

This work focuses on studying the influence exerted on several thermophysical properties of an ionic liquid (IL), 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) by alcoholic solvents, ethanol and 2,2,2-trifluoroethanol (TFE), experimentally and computationally. Herein, the densities, ρ, speeds of sound, u, and dynamic viscosities, η, of the pure IL, [EMIM][DCA]; molecular solvents, ethanol and TFE; and their binary mixtures have been measured over the entire mole fraction ranges at various temperatures from 298.15 to 323.15 K, with an interval of 5 K and at pressure P = 0.1 MPa. The obtained experimental data are utilized to determine the excess/deviation properties, viz., the excess molar volumes, VE, isentropic compressibility deviations, ΔΚs, and viscosity deviations, Δη. The excess/deviation properties of the studied binary mixtures are fitted to polynomial equations of Redlich–Kister type. The dependence of computed parameters on the composition and temperature and the nature of studied systems is discussed in terms of ion–ion, ion–dipole, hydrogen-bonding, and dipole–dipole interactions. The excess molar volumes of each binary system have been correlated with Prigogine–Flory–Patterson theory. To obtain a molecular-level understanding of the interactions between the IL and cosolvent, molecular dynamics (MD) simulations are employed for two different systems as a function of composition at two different temperatures. Along with thermophysical properties such as density and excess molar volume, the self-diffusion coefficient, radial distribution function, and coordination number are also obtained from MD to provide further insights into fluorine-substituted ethanol (TFE) with IL in order to understand the effect of substitution of fluorine in ethanol in the IL + solvent binary systems.