Monte Carlo simulations of liquid spreading on a solid surface: effect of end-group functionality.

The spreading of liquid droplets composed of molecules with or without reactive end groups over a solid surface has been studied using Monte Carlo simulations. For molecules without reactive end groups, a molecular layering in the spreading profiles is predicted, depending on the ratio of the magnitude of intermolecular interactions to thermal energy. As intermolecular interactions become smaller than thermal energy, the layered structure vanishes. For molecules with reactive end groups, interactions between end groups and between end groups and the surface complicate the situation. By assuming an end-to-end interaction between molecules and the pinning of end groups to the surface, a complex layered structure is obtained. Our simulation predicts spreading profiles that accurately describe the broad spectrum of data obtained from scanning microellipsometry for perfluoropolyalkylethers with and without reactive end groups.