Calculation of Disjoining Pressure of Lubricant Films via Molecular Simulation

In this study, disjoining pressure of molecularly thin film on a solid surface is calculated from molecular dynamics simulation for the first time. Disjoining pressure in such thin films has been measured using a geometry in which the film and a curvature coexist so that the disjoining pressure is obtained indirectly from capillary pressure due to the curvature. An off-lattice, coarse-grained, bead-spring model used in the simulations is described in a previous report (Q. Guo et al.). A simulation cell with a rectangular plate in xy plane is used to obtain 2-dimensional fluid bridge between the plates facing each other. The bridge shape is reproduced by the augmented Young-Laplace equation (AYLE) with the thickness of the coexisting film and the surface tension of the polymers as input parameters. The surface tension is obtained separately from the molecular dynamics simulations using the same bead-spring chains.