Tailoring Deep Eutectic Solvents: The Role of Hydrated Metal Salts in Modifying Structural Organization and Macroscopic Performance

Abstract

Deep eutectic solvents (DES) have emerged as promising green alternatives to conventional solvents; however, their broader implementation remains limited by the scarcity of reliable thermophysical and interfacial property data, particularly for multicomponent systems. In this work, a systematic experimental characterization was carried out on a ternary DES based on ChCl:Gly (1:2) incorporating hydrated metal salts. Systems containing AlCl3·6H2O, MgCl2·6H2O, Mg(NO3)2·6H2O, and CaCl2·2H2O are prepared at metal salt molar fractions ranging from 0.10 to 0.35. Density, viscosity, speed of sound, surface tension, and contact angle are measured over the temperature range of 293.15–343.15 K at atmospheric pressure. Experimental density, viscosity, and speed-of-sound data were correlated using empirical regression models, providing accurate descriptions of their temperature dependence and enabling predictive capability. Surface tension and contact angle measurements are used to assess interfacial behavior and wettability, revealing clear dependencies on DES composition and substrate nature. Overall, this work provides a consistent data set of bulk and interfacial properties for these choline chloride:glycerol:metal salt hydrated DES systems, contributing to improved structure–property understanding and supporting their rational design and application in process-oriented systems.