Hydrophobic coating of mica by stearic acid vapor deposition

We report on the preparation of thin films of stearic acid on mica by sublimation in air. We correlate their affinity to water (hydrophobic vs. hydrophilic character) to the morphology of the films as observed by Atomic Force Miscorcopy (AFM). Submonolayer and monolayer coverage exhibited hydrophilic character with dendritic shape defective self-assembled monolayer structures. With further exposure to stearic acid regular polyhedric multilayer three-dimensional structures formed on top of the monolayer, following the Stranski-Krastanov mechanism of growth. These structures were found to be compatible with a stearic acid bulk crystal structure. Coalesce of the structures generated a hydrophobic multilayer coating showing spiral growth. However, the multilayer coating was not homogeneous showing areas with only defective monolayer coating that still exposes bare mica. (C) 2013 Elsevier B.V. All rights reserved.