Optically transparent superhydrophobic TEOS-derived silica films by surface silylation method

Optically transparent silica films were prepared at room temperature (similar to 27A degrees C) by keeping the molar ratio of TEOS:MeOH:H2O (0.001 M NH4F) constant at 1:19.29:6.20, respectively. A surface chemical modification of the films was done with alkylchlorosilanes at different concentrations from 0 to 1 vol. % and aging times varied from half to 2 h. The DMCS and TMCS surface modified silica films showed the static water contact angle of 146A degrees and 162A degrees, respectively. When the DMCS and TMCS modified films were cured at temperatures higher than 240 and 275A degrees C, respectively, the films became superhydrophilic. Further, the humidity study was carried out at a relative humidity of 90% at 30A degrees C temperature over 60 days. We characterized the water repellent silica films by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, % of optical transmission, humidity tests and contact angle measurements.