Molecular Dynamics Studies of Mixtures of a Deep Eutectic Solvent and Cosolvents

All-atom molecular dynamics simulations have been performed on mixtures of tetrabutylammonium chloride-based deep eutectic solvent and two cosolvents — methanol and acetonitrile. Water, a highly polar protic solvent, strongly interacts with the DES components. Herein, we have chosen methanol, a protic solvent but less polar than water, and acetonitrile, an aprotic solvent, to investigate the structural modifications in DES and new interactions arising after the addition of cosolvent based on both polarity and the presence or absence of labile hydrogen. Of the two cosolvents, methanol is found to affect the interactions present in DES significantly. Strong hydrogen bond interaction occurs between the chloride anion and methanol, leading to changes in the behavior of the mixture at the microscopic level. The self-diffusivity of components of the DES increases with the addition of methanol and acetonitrile; however, the increase is relatively more significant in the latter due to fewer average numbers of H-bonds. The amplitudes of the peaks of the structure factor decrease with an increase in the cosolvent concentration, thereby confirming that cosolvent affects the long-range correlations.