Using Molecular Dynamics Simulations to Understand the Effect of Fatty Acids Chain Length on Structural and Dynamic Properties of Deep Eutectic Solvents Based on Choline Chloride and Fatty Acids

Abstract The binary mixtures of choline chloride and a series of fatty acids such as Caprylic acid (C8), Capric acid (C10), Lauric acid (C12), Myristic acid (14), and Palmitic acid (C16) have been prepared. The structural and dynamical properties of the eutectic mixture with the constant molar ratio of Ch + Cl − : FAs=1 : 1 was evaluated at 353 K. To analyze the intermolecular interactions in the binary mixtures, the 100 ns MD simulation was implemented using the NPT ensemble. The structure and properties of the binary mixtures were investigated to understand their molecular interactions. The results confirmed that the interaction between chloride ions and fatty acids has played an important role in interrupting the main interaction between the acids in the pure state. However, Interactions between chloride anion and the hydroxyl group of cations are more weakened in the presence of FAs with a shorter chain length. It is well known that there is a similar relationship between the intermolecular interactions and dynamics properties in distinctive structures of DES. Therefore, the other theme of this study is exploring the possible effect of intermolecular interactions on the self‐diffusion coefficients of species and determining the fatty acids that have stronger interactions with choline chloride salt to form the eutectic solvents. The diffusion coefficient of species was calculated by Einstein's equations. The results of dynamics properties showed the strong Hydrogen bonding network of the binary mixture of Caprylic acid and Choline chloride strongly affects molecular migrations.