Surface Tension of 50 Deep Eutectic Solvents: Effect of Hydrogen-Bonding Donors, Hydrogen-Bonding Acceptors, Other Solvents, and Temperature

Surface tension is a key physiochemical property for the application of deep eutectic solvents (DESs) in the field of interface and colloid. However, the surface tension of DESs has not been systematically studied. Here, a comprehensive investigation on the surface tension of 50 typical DESs was carried out. The effect of hydrogen-bonding donors (HBDs) and hydrogen-bonding acceptors (HBAs) on the surface tension was investigated. Furthermore, the surface tension of mixed systems of DESs with other solvents, water, water+salt (e.g., KCl), ethanol, acetone, isopropyl alcohol, and ethyl acetate (EtAc), was studied. It was found that both HBDs and HBAs had a significant influence on the surface tension of DESs. The presence of crystal water in the salt component of DESs would decrease the surface tension of DESs. Besides, the surface tension of DESs increased significantly when the water mole fraction was higher than 0.9, which was well consistent with the tendency of IR spectra. However, the surface tension of DESs decreased continuously with the increase of the mole ratio of other investigated solvents.