The interaction of oligo(ethylene oxide) with water: a quantum mechanical study

Using density functional theory with nonlocal corrections we have performed a systematic study of the molecular conformation and energetics of methoxy terminated oligo(ethylene oxide) (EG)n molecules. For n=3 we have calculated 31 conformers without and with adsorbed water, and made some comparisons with n=1, 2 and selected n=4 conformers. We find that solvated EG moieties with non-uniform gauche rotations are by far the most stable in the solvated state. We also examine rotational barriers around the C–O and C–C bonds. In addition, using the calculated energies and vibrational spectra of the dry and solvated EG strands and the tabulated thermodymamical functions of water we can estimate the enthalpy and entropy contribution to the free energy of solvation.