Tapping Mode AFM Studies of Nano-Phases on Fluorine-Containing Polyester Coatings and Octadecyltrichlorosilane Monolayers

• Published in: Langmuir 1998-05, Vol.14 (11), p.3045-3051
• Main Authors: Sauer, Bryan B, McLean, R. Scott, Thomas, Richard R
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solid-liquid interface; Surface physical chemistry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la971334d

Lightly cross-linked films were made by solvent casting hydrocarbon polyester solutions containing trace fluorocarbon in the bulk and then curing or cross-linking the film to anchor the fluorine groups. The surface nano-morphology was studied by AFM techniques based on tapping mode AFM which allows very low contact forces and gives indirect surface chemical mapping of different domain morphologies with high lateral resolution. The contrast is usually from different local stiffness variations of domains at or near the surface. More conventional friction force microscopy techniques were also applied to verify the results. The percent coverage of fluorine-rich domains was quantitatively related to that determined from hexadecane contact angles. A low-coverage self-assembled octadecyltrichlorosilane (OTS) monolayer system, exhibiting nano-patches on Si substrate, was used as a control for a newly applied ultra-light-tapping technique which derives its chemical resolution from hydrophilicity differences of the phases at the surface. The hydrophilicity differences possibly modify the water meniscus forces on the scanning tip and allow indirect assignment of domains based on different hydrophilicities in cases where there are no a priori stiffness assignments of the different domains.