Preparation of superhydrophobic silica-based films by using polyethylene glycol and tetraethoxysilane

Preparation of superhydrophobic silica-based films via sol-gel process by adding polyethylene glycol (PEG4000) in the silica sol precursor solution has been developed. The casting films were prepared by casting the above solution on the glass and adding poor solvent on it or not. Surface roughness of the films was obtained by removing polymer from the films at high temperature. Then, the hydrophobic group on the surfaces was obtained by reaction with hexamethyldisilazane (HMDS). Characteristic properties of the as-prepared surface of the films were analyzed by contact angle measurement, scanning electron microscopy (SEM), atomic force microscope (AFM), Fourier transform infrared (FT-IR) spectrophotometer, and X-ray photoelectron spectrometer (XPS). The results showed that the contact angles of the films were varied with the PEG weight fraction of the films, the solvent for the PEG solution, the reaction temperature and time, and adding poor solvent (n-hexane) or not. However, the surface roughness has been controlled by adjusting the experimental parameters during the early period. The contact angle of the film that prepared by spraying the poor solvent (n-hexane) onto each coating layer for four times after casting process was greater than 150 degrees. It was difficult to obtain superhydrophobic surface without adding nhexane onto any coating layer in this system. (c) 2007 Wiley Periodicals, Inc.