Structure and dynamics of thymol - fatty acids based deep eutectic solvent investigated by molecular dynamics simulation

The current work focuses on the design of hydrophobic eutectic solvents (HDESs) based on Thymol and fatty acids and the investigation of their dynamical and structural properties. Binary mixtures of Thymol and fatty acids such as Caprylic acid (C8), Decanoic acid (C10), Lauric acid (C12), and Myristic acid (C14) were prepared at different ratios. Molecular dynamics simulations were carried out to evaluate the change in the percentage composition of the designed DESs on the bulk properties at the temperature of 323 K. The percentage composition of the binary mixtures that have the most intermolecular interaction between the donor and the acceptor of the hydrogen bond was selected, and their thermos-physical properties were investigated at different temperatures. The analysis of atom-atom radial distribution functions (RDFs), spatial distribution functions (SDFs), the energy of non-bonded interactions, and the Hydrogen bonding network between Thymol molecules and fatty acids were obtained to understand effective interactions in binary mixture formation. The evidence was found for the hydrogen bonds with the more significant percent occupancies between Thy and FAs in the angular/distance probability region at around 150°−180°/2 Å. The results of MD simulations showed that the intermolecular interactions were impacted in the pure state by interactions between the hydroxyl group of Thymol and fatty acids, and the main interactions interrupt. Dynamical properties of the eutectic mixtures were investigated by the mean-square displacement (MSD) and the self-diffusion. The strong Hydrogen bonding network of binary mixture led to changes in the molecule migration. The intermolecular interaction understanding will aid in determining suitable ratios for the design of eutectic solvents. Finally, we proposed possible explanations for the composition of the appropriate percentage for the formation of the eutectic solvent.