Excess Thermodynamic and Acoustic Properties of Aqueous Choline Chloride-Glycerol Deep Eutectic Solvent: Insight into Intermolecular Interactions

Deep eutectic solvents (DESs) have emerged as environmentally benign alternatives to conventional solvents owing to their tunable physicochemical properties and molecular interactions. In the present study, a choline chloride-glycerol DES (1:3 molar ratio), denoted as choligly-DES, was synthesized via a heating-stirring method. The physicochemical behavior of aqueous choligly-DES was investigated over the entire composition range at temperatures from 288.15 to 323.15 K at intervals of 5 K. Experimental measurements of density, speed of sound, and viscosity were performed for the choligly-DES + water binary mixtures. From these data, excess molar volume(VmE), excess isentropic compressibility (Ks,Em), intermolecular free length (LfE), excess speed of sound (cE), acoustic impedance (ZE), viscosity deviation (Δη), and the excess Gibbs free energy of activation of viscous flow (G*E) were evaluated and correlated using the Redlich–Kister polynomial equation. To obtain deeper insight into the solution structure, partial molar volumes (V̅m,1 and V̅m,2) and excess partial molar volumes ( V¯m,1E and V¯m,2E) of the components were also determined. These findings provide valuable insight into the molecular organization and interaction mechanisms of aqueous choligly-DES systems.