Microscopic spreading of nonreactive perfluoropolyalkylether film on amorphous carbon surfaces

A spreading mechanism of nonfunctional perfluoropolyallcylehter (PFPE) on c arbon surfaces is proposed. For the thin thin-film regime, adsorption-desor ption is a main driving force for spreading, and the surface diffusion coef ficients increase as the film thickness increases. A two-dimensional virial equation is employed to explain the dependency of surface diffusion coeffi cient on the film thickness. For the thick thin-film regime, the spreading characteristic is determined by the disjoining pressure gradient. We adopt a slip boundary condition to analyze the thick thin-film regime. This modif ication of the boundary condition reasonably explains the dependence of sur face diffusion coefficients on film thickness.