Excess properties and activation properties for viscous flow of amino acid ionic liquids with H2O binary mixtures

Abstract

Amino acid ionic liquids (ILs) 1-butyl-2,3-dimethylimidazolium glycine ([C4Dmim][Gly]), 1-butyl-2,3-dimethylimidazolium alanine ([C4Dmim][Ala]) and 1-butyl-2,3-dimethylimidazolium threonine ([C4Dmim][Thr]) were prepared. Over the temperature from (288.15–318.15) K, the density, surface tension and viscosity for binary system mixtures of ILs with H2O were measured, and excess thermodynamic properties and activation properties for viscous flow of these binary system mixtures were systematically studied. Secondly, the variation trend between excess molar volume (VE)/excess molar surface Gibbs energy (gsE) and mole fraction for ILs + H2O binary system mixtures was investigated. With the increase of mole fraction, the VE and gsE values of binary system mixtures increased firstly and then decreased, and they were positive value, which may be due to the weak chemical interaction between ILs and H2O in the mixture. Furthermore, according to the thermodynamic formula, the Gibbs energy of activation for viscous flow of the relative viscosity (ΔG≠r), activation entropy (ΔS≠r) and activation enthalpy (ΔH≠r) were calculated. Over the entire concentration range, the ΔG≠r values for binary system mixtures of ILs with H2O were negative value, and the result was in good agreement with relative viscosity (ηr).