SOLUTE ORIENTATIONAL DYNAMICS AND SURFACE-ROUGHNESS OF WATER HYDROCARBON INTERFACES

Molecular dynamics simulations of two model water/alkane interfaces are used to sort out the effect of molecular shape on the structure and dynamics of the neat interfaces and the orientational dynamics of a solute adsorbed at the interface. The two liquid/liquid interfaces are the water/nonane interface and the one between water and a single atom representation of the nonane molecule whose potential energy function is selected to give properties close to that of nonane. We find that although the thermodynamic properties and relevant structural properties of the two interfaces are very similar, the reorientation dynamics of the solute probe are faster by about a factor of 2 in the water/''spherical''-nonane system due to different molecular packing and shape.