Molecular dynamics investigation of hydration of nanoscopic hydrophobic paraffin-like plates

Abstract

The effect of surface characteristics on the hydration behavior of various paraffin-like plates has been investigated. Structure and orientation characteristics of the water molecules in the solvation shells of various nanoscopic paraffin-like plates differing from each other in the intermolecular spacing have been extensively studied using molecular dynamics simulation in isothermal-isobaric ensemble. Single particle density distribution of water molecules around the plate reveals well defined solvation shells around each of the paraffin-like plates studied here. A sharp first peak in the density profile in each of the plates signifies no visible dewetting around the paraffin plate. Instantaneous density of water molecules around the plate also reveals that the plate is sufficiently hydrated and there is no intermittent fluctuation in water density in the first hydration shell leading to short lived dewetted state for any of the model plates within the two nanosecond time span. This is in contrast to the hydration behavior of the intersolute region, where intersolute dewetting has been observed for some of the model plates. Thus the present results demonstrate that dewetting in the intersolute region of nanoscopic hydrophobic plates does not stem from drying interface of the individual solute. No significant effect of surface topology on the orientational structure of water molecules as revealed through distributions of dipole moment as well as oxygen-hydrogen bond vectors of a water molecule in different solvation shells has been observed.