The interaction of pseudo-binary system of DES (1TEAB: 3EG) with acetonitrile, ethanol and water by volumetric properties, surface properties and refractive properties

Deep eutectic solvents (DESs) as the novel kind of green solvents have been received widespread attention. After the addition of molecular solvents, a pseudo-binary system is set up with the advantages such as low cost. A kind of DES (1TEAB: 3EG) was prepared and confirmed, and it is mixed with acetonitrile, ethanol and water. Their density, surface tension and refractive index of the DES and its corresponding pseudo-binary mixtures are explored in depth. In addition to the excess molar volumes, the partial molar volumes, partial molar volume at infinite dilution and their excess molar volumes are also investigated. The molar Gibbs free energy and the corresponding molar surface enthalpy could be deduced from the improved Eӧtvӧs equation. It is suggested that the molar Gibbs free energy model is fit for that of DES and its pseudo-binary systems. In addition, the surface tension deviations and refractive index deviations are figured out. This illustrates that there are fairly strong interactions between DES (1TEAB: 3EG) and molecular solvents, which could attribute to mainly two sides: H-bonding and structural effect. Besides, refractive properties such as the molar refraction and free volume are advised that there are ion–dipole interactions between DES and molecular solvents. Graphical abstract