Simulation of ultrathin lubricant films spreading over various carbon surfaces

The mathematical modeling of the dynamics of ultrathin perfluoropolyalkylet her (PFPE) films, taking into consideration both the disk carbon surface co mposition and lubricant endgroup functionality, is described. Theoretical d evelopment based on the Monte Carlo method was employed to emulate experime ntal spreading data. In this model, we construct a system Hamiltonian based on a lattice-gas model by explicitly incorporating four classes of interac tions: molecule/molecule, molecule/surface, endgroup/endgroup, and endgroup /surface, where a molecule is denoted as a backbone in the absence of endgr oups. Spreading properties are investigated by tuning the lubricant interac tions to model PFPE Z (without polar endgroups) and PFPE Zdol (with polar e ndgroups) on several surfaces. The simulations qualitatively describe the s preading profiles for molecules with and without polar endgroups. Acquired from N-frame animations, L-t plots are constructed and provide a qualitativ e comparison with the experimental data obtained from scanning microellipso metry. (C) 2000 American Institute of Physics. [S0021-8979(00)39408-7].