Interfacial Structures, Surface Tensions, and Contact Angles of Diiodomethane on Fluorinated Polymers

Abstract

The wetting behavior of diiodomethane on crystalline poly(tetrafluoroethylene) (PTFE), noncrystalline PTFE, and poly(vinylidene cyanide-alt-1H,1H,2H,2H-perfluorodecyl vinyl ether) surfaces are analyzed theoretically. By combining three-dimensional reference interaction site model with three-dimensional density functional theory, the theory provides the overall density and free-energy distributions of diiodomethane at the three surfaces. It is shown that surface roughness arising from polymer structure and configuration plays the crucial role in the surface tension and the wettability. Meanwhile, the contribution of chemical composition is also important to the surface tension by altering the intra- and intermolecular interactions and renormalizing the surface roughness. The predicted contact angles of a diiodomethane droplet on the three surfaces are in good agreement with the available experimental values, showing the theory is able to quantitatively evaluate the cooperative contributions of chemical composition and geometry to wettability.