Thermodynamic properties of binary systems containing 1-allyl-3-methylimidazolium dicyanamide [Amim][DCA] with short chain alcohols and prediction of surface tension based on molar surface Gibbs free energy

Abstract

BackgroundAllyl functionalized ionic liquids (ILs) are widely used because of their excellent properties, to increase their applications in industry and academic community, preparing binary mixtures containing ILs and organic solvents is an effective way, and it is essential to further explore the thermodynamic properties of them. MethodsHere, we reported the synthesis and characterization of the ILs 1-allyl-3-methylimidazolium dicyanamide [Amim][DCA]. Then, in the temperature range of 288.15 K–318.15 K, the values of density and surface tension of 1-allyl-3-methylimidazolium dicyanamide, methanol, ethanol, propanol and corresponding binary systems were measured at every 5 K in the full molar concentration. The values of surface tension deviation Δγ, excess molar volume VE and molar surface Gibbs free energy gs of the mixtures were calculated. In addition, the modified Eӧtvӧs equation is derived based on gs, and the values of surface tension of binary mixtures are estimated. Significant findingsThe results show VE are negative, which is mainly due to the tight packing and hydrogen bond, the formation of hydrogen bond has been confirmed by infrared spectroscopy. The Δγ values of 1-allyl-3-methylimidazolium dicyanamide + methanol are positive, while that of the other two are negative. The modified Eӧtvӧs equation has a clear physical meaning. Moreover, the predicted values are in good agreement with the measured ones.