Due to their neoteric nature, deep eutectic solvents (DES) and their mixtures surpass conventional organic and ionic liquids as solvents. DES are considered environmentally friendly alternatives to traditional organic solvents due to their low toxicity, biodegradability, and abundant natural components. They exhibit unique properties such as low volatility, high thermal stability, and tunable polarity, making them versatile in various applications, including green chemistry, extraction processes, catalysis, and electrochemistry. DES have garnered significant attention in recent years as sustainable alternatives to conventional solvents in various industrial processes [1]. 

Computational and experimental techniques are complementary for determining the structure, design and thermo-physical properties of liquids and their mixtures. Various researchers [2, 3] employed Density Functional Theory (DFT), Molecular Dynamics (MD), COSMO-R and Flory’s Statistical theory (FST) to estimate these properties. Though these theoretical formulations are found suitable to compute the thermo-physical properties, FST is a valuable and powerful tool because of the limited input parameters and ease of calculations. FST is a good candidate in the theoretical framework of industrial design to predict the thermodynamic properties [4].

In the present investigation, several important thermophysical properties, such as density, isothermal compressibility, and internal pressure, are predicted using Flory’s Statistical Theory (FST) for four three-component DES mixtures, at different concentrations and temperatures.  The mixtures chosen for investigation are (i) choline chloride/lactic acid/ethylene glycol (Ch/LA/EG) + Water, (ii) choline chloride/lactic acid/glycerol (Ch/LA/G) + Water, (iii) choline chloride/oxalic acid/ethylene glycol (Ch/OA/EG) + Water, and (iv) choline chloride/oxalic acid/glycerol (Ch/OA/EG) + Water. ures. 

The theoretically computed values of the parameters under study show good agreement with the corresponding experimental values for mixtures under investigation. Based on the obtained results, it is evident that FST can predict these physical properties for the DES mixtures under study, in the given range of concentrations and temperatures. Furthermore, additional thermophysical properties, viz., enthalpy of vaporization, cohesive energy density, and solubility parameter, are also determined for various concentrations and temperatures to understand the nature and types of molecular interactions prevalent in these mixtures. The present study provides a much deeper insight into the functionality of the given DES mixtures as an industrial solvent.