OTES modified transparent dip coated silica coatings

Abstract The present paper describes the room temperature synthesis of dip coated water repellent silica coatings on glass substrates using octyltriethoxysilane (OTES) as a co-precursor with two-step sol–gel process. Silica sol was prepared by keeping the molar ratio of tetraethylortosilicate (TEOS) precursor, methanol (MeOH) solvent, acidic water (0.001 M oxalic acid) and basic water (12 M NH 4 OH) constant at 1:11.03:0.17:0.58 respectively, throughout the experiments and the OTES weight percentage was varied from 0% to 15%. It was found that with an increase in wt% of OTES, the roughness and hydrophobicity of the films increased, however the optical transmission decreased from 93% to 88% in the visible range. The hydrophobic silica films retained their hydrophobicity up to a temperature of 259 °C and above this temperature, the films became hydrophilic. The hydrophobic silica thin films were characterized by taking into consideration the surface roughness studies, Fourier transform infrared (FT-IR) spectroscopy, percentage of optical transmission, scanning electron microscopy (SEM), Thermogravimetric-differential thermal analysis (TG-DTA) and contact angle measurements.