Molecular Dynamics Simulation of 1,2-Dimethoxyethane/Water Solutions. 2. Dynamical Properties

We have performed molecular dynamics simulations of 1,2-dimethoxyethane (DME)/water solutions at 318 K in order to examine conformational, translational, and rotational dynamics of the solutions as a function of composition. The rate of conformational transitions for the C−O—C−C and the O−C—C−O dihedrals in DME decreases with increasing water content for mole fraction X DME ≥ 0.18. For more dilute solutions, the conformational transition rate is independent of composition. Self-diffusion coefficients of DME and water for X DME ≥ 0.18 indicate that the dynamics of DME and water comprising the first coordination shell of DME are highly correlated. We found that the average residence time of water in the first coordination shell was only about 2 ps and was not significantly longer for water that is hydrogen bound to the DME. For more dilute solutions, the additional water manifests the dynamical characteristics of bulk water. The rotational diffusion coefficient for DME shows qualitatively similar dependence on solution composition to that seen for the DME center-of-mass diffusion. We found that water comprising the first coordination shell of DME showed significantly reduced rotational dynamics compared to those of free water, which closely resembles bulk water.