Can isopiestic method predict the formation of deep eutectic solvents?

Abstract

In order to evaluation of the capability of different hydrogen bond donor (HBD)‑hydrogen bond acceptor (HBA) systems for the formation of deep eutectic solvents (DESs), systematic studies on the vapor-liquid equilibrium behavior of aqueous solutions of choline chloride (ChCl) as a HBA were carried out in the presence of several HBDs. For this purpose, isopiestic equilibrium molalities were obtained for ternary aqueous solutions of ChCl in the presence of different HBDs including Urea, Potassium acetate, Glucose, Furctose, Sucrose, Mannose, Xylose, Citric acid, Malonic acid, Glycerol, Sorbitol, Alanine and PEG600 at 298.15 K. The constant water activity lines showed the positive deviation from the Zdanovskii-Stokes-Robinson rule (semi ideal behavior) for the HBDs which interact strongly with ChCl and forming DESs. However, the negative deviation from the semi ideal behavior was observed for the HBDs which don't interact with the hydrogen bond acceptor and cannot form DESs. Therefore, the results obtained in this work indicate that the isopiestic method can be used for choosing the proper HBA and HBD for the formation of stable liquid DESs at room temperature.