Electrostatics for exploring the nature of the hydrogen bonding in polyethylene oxide hydration

Binding between water and models of poly(ethylene oxide), (CH2-CH2-O)(n), n = 2-40, has been studied using the topographic features of the electrostatic potential, V(r), and standard density functional theory methods. It was found that, in general, the contour around the minima of the oxygen atoms overlap forming a negative-valued spiral coiled around a positive-valued helix. The positive zone defines a helical groove in the O-C-C-O units where minima lone pairs critical points are located. Topological analysis of the water molecule has also suggested that the attractive electrostatic effect between the positive water O-H zone and the negative PEO lone pairs plays an important role in the hydrogen bonding of the PEO-water system. Thus, the V(r) topology predicts a coil of water molecules around the PEO chain forming hydrogen bonding with two sites of ether oxygens. This coil is formed in such a way that more water molecules accumulate on the cavities surrounding the poly(ethylene oxide)'s oxygen atoms where the minima of the negative zone are located.