Quantum-chemistry-based force field for 1,2-dimethoxyethane and poly(ethylene oxide) in aqueous solution

An atomistic force field for simulations of 1,2-dimethoxyethane (DME) and poly(ethylene oxide) (PEO) in aqueous solution is presented. The force field is parametrized to reproduce energies of complexes of DME and water as determined from high-level quantum chemistry calculations. The quantum chemistry calculations reveal that the binding of DME to water is comparable to water-water binding in water dimer, indicating strong hydrogen bonding between DME and water. We find that the binding energy of water to DME in the tgt conformation (-7.7 kcal/mol) is greater than that for the other low energy DME conformers (-6.1 kcal/ mol for ttt and -6.4 kcal/mol for tg(+)g(-) respectively), due to the strong interaction of the water hydrogen atoms with both ether oxygen atoms in the tgt conformer. The accuracy of the force field is verified through a series of molecular dynamics simulations of DME-water solutions performed as a function of temperature and composition. Comparison of simulation values for density, excess volume, and viscosity with experiment indicate excellent agreement. Initial analysis of the calculated conformer populations as a function of composition reveals a strong preference for the tgt conformer in aqueous solution, and analysis of the pair distribution functions appears to be consistent with suggestions that this is due to the compatibility of the DME tgt geometry with the structure of liquid water.