Hydrogen bonding behavior of ethanol-trifluoroethanol binary mixtures and its effects on the water structure and dynamics in ternary aqueous-ethanol-trifluoroethanol solutions

The hydrogen bonding structure and dynamics of binary ethanol (EtOH) - trifluoroethanol (TFE) mixtures and in ternary aqueous-EtOH-TFE solutions are investigated by classical molecular dynamics simulations. Presence of water reduces hydrogen bonds between EtOH and TFE due to formation of new alcohol-water hydrogen bonds. In aqueous-EtOH-TFE mixtures, the tetrahedral order of water increases as we move from water-EtOH to water-TFE solution. Our calculated translational and rotational data suggests a slower dynamic of the species in their binary as well as in the ternary mixtures. The steep rise of the orientational relaxation times for TFE indicates a stronger aggregation among TFE molecules in both binary and ternary mixtures. A faster anisotropic decay of water is also observed with increasing TFE concentrations in the ternary solutions. The hydrogen bond lifetime associated with the hydrogen of TFE (HTMIDLINE HORIZONTAL ELLIPSISOT/OE/OW) is multiple times higher than that of H-bonds formed by the hydrogen of EtOH (HE)/water (HW).

Automated summary

The hydrogen bonding structure and dynamics of binary ethanol-trifluoroethanol mixtures and ternary aqueous-ethanol-trifluoroethanol solutions were investigated through molecular dynamics simulations. Water presence led to a decrease in hydrogen bonds between ethanol and trifluoroethanol due to the formation of new alcohol-water hydrogen bonds. In the ternary solutions, the tetrahedral order of water increased when moving from water-ethanol to water-trifluoroethanol. The species in both binary and ternary mixtures showed slower dynamics, with stronger aggregation and faster decay observed in water with increasing trifluoroethanol concentrations.