Replenishment of Ultrathin Liquid Perfluoropolyether Z Films on Solid Surfaces

Abstract

Applying the reptation algorithm to a simplified perfluoropolyether Z off-lattice polymer model an NVT Monte Carlo simulation has been performed. Bulk condition has been simulated first to compare the average radius of gyration with the bulk experimental results. Then the model is tested for its ability to describe dynamics. After this, it is applied to observe the replenishment of ultrathin (4 nm thickness) liquid films on solid flat carbon surfaces. The replenishment rate for trenches of different widths (8, 12 and 16 nm for molecular weight of 3840 g/mol and 12 nm for molecular weights of 2500 and 1700 g/mol) between two films of perfluoropolyether Z from the Monte Carlo simulation are compared to those obtained solving the diffusion equation using the experimental diffusion coefficients of Ma et al. with room condition in both the cases. Replenishment per Monte Carlo cycle seems to be a constant multiple of replenishment per second at least up to 2 nm replenished film thickness of the trenches over the carbon surface. Considerable good agreement has been achieved here between the experimental results and the dynamics of molecules using reptation moves in the ultrathin liquid films on solid surfaces.