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 (Gij) in the Grunberg–Nissan
mixing rule. It was found that the temperature-dependent Gij yields better results for modeling
the viscosity of ChCl-based DESs, whereas the composition-dependent Gij 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.