Effect of nano-trenches on the ultrathin liquid polymer film spreading and free surface undulations on solid surfaces

Abstract

An NVT Monte Carlo (MC) simulation for perfluoropolyether (PFPE) Z was performed using a Rouse-like algorithm applied to a simplified bead-spring off-lattice polymer model. A bead-bead Lennard-Jones (LJ) potential and a substrate-bead LJ potential were used. Simulations were performed with 2000 and 4000 g/mol molecular weights, assuming room temperature and pressure conditions. It was observed that the calculated average radius of gyration (Rg) for bulk condition is almost equal to the bulk experimental value. An ultrathin liquid film of about 2 nm film thickness was, first, equilibrated on a flat carbon surface. Then, this film was allowed to spread under the influence of dispersive interaction with the flat surface. A nano-scale trench was made parallel to the spreading edge and the film was allowed to spread across the trench. Several trench widths and depths were used in different simulation platforms. The spreading rate of the spreading over a flat surface was compared with those over the trenched surfaces. Moreover, the effects of these nano-scale trenches over the undulations of the free surfaces were observed and analysed with respect to different trench widths and depths as well as molecular weights.