Modeling the Viscosity of ChCl-Based Deep Eutectic Solvents and Their Mixtures with Water

Choline chloride (ChCl)-based deep eutectic solvents (DESs) are emerging as promising environmentally friendly alternatives to conventional organic solvents across various applications. However, their relatively high viscosity necessitates careful assessment before implementation. This work proposes an approach to modeling the viscosity of ChCl-based DESs and their mixtures with water using the Grunberg–Nissan mixing rule. We assumed that the viscosity of the hypothetical liquid ChCl could be calculated by the Vogel–Fulcher–Tammann (VFT) model. The VFT parameters of ChCl were regressed using the viscosity data of 17 ChCl-based DESs at various compositions and temperatures. The obtained VFT parameters of ChCl allowed modeling of the viscosity of eight newly measured DESs and their mixtures with water. Five methods were investigated to calculate the interaction parameter (G_ij) in the Grunberg–Nissan mixing rule. It was found that the temperature-dependent G_ij yields better results for modeling the viscosity of ChCl-based DESs, whereas the composition-dependent G_ij is more suitable for modeling the viscosity of mixtures of DESs and water. The proposed viscosity modeling approach can significantly reduce the experimental effort required to obtain reliable viscosity estimations for ChCl-based DESs and their mixtures with water.