The Molecular Spreading of Nonpolar Perfluoropolyether Films on Amorphous Carbon Surfaces

• Published in: Journal of colloid and interface science Vol. 228; no. 2; pp. 405 - 409
• Main Authors: Kim, Min C., Phillips, David M., Ma, Xiaoding, Jhon, Myung S.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15.08.2000; Elsevier
• Subjects: Applied sciences; disjoining pressure; Exact sciences and technology; Organic polymers; perfluoropolyether; Physicochemistry of polymers; Properties and characterization; scanning microellipsometry; spreading; surface diffusion; Surface properties; spreading; disjoining pressure; scanning microellipsometry; perfluoropolyether; surface diffusion; Liquid film; Fluorine containing copolymer; Molten state; Ether copolymer; Surface diffusion; Experimental study; Carbon; Modeling; Mechanism; Molecular weight property relation; Spreading; Size effect; Aliphatic copolymer
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.2000.6978

The spreading mechanism of nonpolar perfluoropolyether films on carbon surfaces is examined in the mesoscopic regime, including both submonolayer and multilayer films. For the submonolayer film, adsorption–desorption is a main mechanism for spreading, and the surface diffusion coefficients increase as the film thickness increases. The driving force for the spreading in the submonolayer regime is the gradient of the disjoining pressure, which is described by the two-dimensional virial equation. For the multilayer film regime, the spreading characteristics are determined by the molecular weight and the disjoining pressure gradient, which is assumed to be purely van der Waals in nature. We adopt a partial slip boundary condition to analyze the multilayer film, which qualitatively explains the dependence of the surface diffusion coefficient on film thickness.