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

Abstract

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 g 0.18. For more dilute solutions, the conformational transition rate is independent of composition. Self-diffusion coefficients of DME and water for X DME g 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.

Solvation effect on conformations of 1,2:dimethoxyethane: Charge-dependent nonlinear response in implicit solvent models

“…(17) (18) Eliminating F from Eq. (18) as before produces the ratio (19) As mentioned earlier, the gas phase dipole moment is ; hence, the static, low frequency bulk dielectric constant ε 0 is related to the molecular electrical polarizability and the dipole moment of the molecules through, (20) Combining the two equations (19) and (20) to eliminate α yields . Introducing this relationship into Eq.…”

“…The PEO/water system has been extensively studied by Smith and coworkers with molecular dynamics simulations. 20 The use of an implicit solvent model would reduce the computational cost of simulating the dynamic and equilibrium properties of PEO by at least two orders of magnitude and would facilitate the study of more complex systems. As a first step towards developing an implicit solvent model for describing the structure and dynamics of PEO in aqueous solutions, we consider its building block, namely DME, the shortest ether molecule that reproduces the local conformations of PEO.…”

“…5 The predictions of this model are compared with explicit solvent simulations for the equilibrium conformational populations of 1,2-dimethoxyethan (DME), which is the shortest ether molecule to reproduce the local conformational properties of polyethylene oxide (PEO). 20 Because the conformational population preferences of DME change dramatically upon solvation, 20 DME provides an excellent system for validating the modified LD (qLD) model. Finally, Section VIII discusses the features of qLD and their relation to other commonly used continuum dielectric models in implicit solvent simulations.…”

Replacement micro-mechanism of CH4 hydrate by N2/CO2 mixture revealed by ab initio studies

“…Assuming that the Debye theory of rotational relaxation is application [50], the rotational correlation times (t) are inversely proportional to rotational diffusion coefficient. From Fig.…”

Effect of Cross-Linking on the Diffusion of Water, Ions, and Small Molecules in Hydrogels

“…The electrostatic interaction energy components were subtracted from the total binding energies by the Coulomb potential using the partial changes on PEG and water molecules shown in Table 3.2 and 3.8. The remaining binding energy components were fitted to the LJ potential using least square fitting method to obtain the LJ parameters [69,70,68]. In order to verify the interaction parameters between PEG and water, we simulated a system composed only of DME chains and water (the mole fraction of DME is 0.04) and calculated the radial distribution function of the oxygen of the DME with the oxygen of water and obtained good agreement with the results of Borodin et al [68], as shown in Figure 3.4.…”