Super-Hydrophobic and Oloephobic Crystalline Coatings by Initiated Chemical Vapor Deposition

Abstract

Preferred crystallographic orientation (texture) in thin films frequently has a strong effect on the properties of the materials and it is important for stable surface properties. Organized molecular films of poly-perfluorodecylacrylate p(PFDA) were deposited by initiated Chemical Vapor Deposition (iCVD). The high tendency of p(PFDA) to crystallize has been fully retained in the polymers prepared by iCVD. The degree of crystallinity and the preferred orientation of the perfluoro side chains, either parallel or perpendicular to the surface, were controlled by tuning the CVD process parameters (i.e. initiator to monomer flow rate ratio, filament temperature, and substrate temperature). Super- hydrophobicity (advancing water contact angle, WCA, of 160°, low hysteresis of 5°), and oleophobicity (advancing CA with mineral oil of 120°) were achieved. Low hysteresis was associated with high crystallinity, particularly when the orientation of the crystallites resulted in the perfluoro side groups being oriented parallel to the surface. The latter texture resulted in smoother film (RMS roughness < 30 nm) than the texture with the chains oriented perpendicularly to the surface. This can be very advantageous for applications that require smooth but still crystalline films.