The study of structure and interactions of glucose-based natural deep eutectic solvents by molecular dynamics simulation

Abstract

In the current study, molecular dynamics simulations were conducted to investigate the structural and dynamical properties of glucose-based Deep Eutectic Solvents (DESs) at different molar ratios (the mixture of glucose and choline chloride with the molar ratios of 1:3, 1:1 and 3:1). Accordingly, the interaction energies of different species and structural properties such as atom–atom radial distribution functions (RDFs), the hydrogen-bonding network between species, and spatial distribution functions (SDFs) were computed to understand effective interactions in the eutectic mixture formation. It was found that the insertion of glucose molecules reduced the accumulation of chloride anions around choline cations, eventually decreasing the interaction between the choline chloride ion pairs. Moreover, the possible explanations for the thermos-physical properties of DESs, such as the shear viscosity and density, have been provided. Dynamical properties of DES were evaluated by calculating the mean-square displacement (MSD) and the velocity autocorrelation function (VACF) for the centers of the mass of the ions and glucose molecules. MSD analysis results were then used to calculate the self-diffusion parameter by applying the Einstein relation. The simulation results indicated that increasing the temperature led to easing the migration of the molecules and decreasing the dependence of the movement of the molecules on each other. This growing trend of migration may lead to an increase in the self-diffusion coefficient of molecules. Structural analysis revealed that a ratio of 1:1 of glucose: choline chloride could provide the best condition to maintain the low melting point of the mixture due to the strong hydrogen-bonded network between the two species.