Theoretical investigation on the structure and physicochemical properties of choline chloride-based deep eutectic solvents

Abstract

Deep eutectic solvents (DESs) are analogous to ionic liquids that have been widely employed in scientific research and engineering applications. The physicochemical properties of DESs, including the density, viscosity, and nanostructure, serve as the foundation for green solvent development. In the present work, the density and viscosity of choline-based DESs at 293.15–353.15 K were simulated using molecular dynamics (MD) simulation under the Generation Amber Force Field. The radial distribution function (RDF) and number of hydrogen bonds of the selected systems were analysed. It was found that a large amount of the hydrogen bonding network was formulated between chlorine and hydrogen atoms in hydroxyl groups, which greatly decreased the melting temperature of the solvent in comparison with the pure components. The intermolecular interaction decreased with increasing temperature as well as the length of the alkyl chain on the hydrogen bond donor (HBD). Furthermore, an increase in the number of hydroxyl groups in HBD molecules leads to the formation of a more complex and extensive hydrogen bond network, which results in a higher viscosity of the DES.