Surface tension and surface thermodynamic properties of PEG-based deep eutectic solvents

Polyethylene glycol (PEG)-based deep eutectic solvents (DESs) emerge as a new class of DESs and have attracted great attention. Surface tension and surface thermodynamic properties are key physiochemical parameters for better utilization of PEG-based DESs. However, surface-related physical parameters of PEG-based DESs have not been investigated. Here, comprehensive investigation on surface tension, surface thermodynamic properties and the corresponding factors (e.g., hydrogen-bonding donor, component type, temperature, water, organic solvent, inorganic salt solution, molecular weight of PEG, concentration and mole ratio) were carried out. Moreover, PEG-based DESs dissociation in water was investigated and it was found that DESs would almost dissociate in water at the concentration of around the turning point at x(H2O) = 0.9, however, no such a turning point of dissociation would exist in other solvents. (C) 2020 Published by Elsevier B.V.