The present paper describes the room temperature synthesis of dip coated water repellent silica coatings
on glass substrates using trimethylethoxysilane (TMES) as a co-precursor. Silica sol was prepared by
keeping the molar ratio of tetramethoxysilane (TMOS) precursor, methanol (MeOH) solvent, water (H2O)
constant at 1:29.27:2.09 respectively, with 0.5 M NH4OH throughout the experiments and the TMES/
TMOS molar ratio (M) was varied from 0 to 3.8. It was found that with an increase in M value, the
roughness and hydrophobicity of the films increased, however the optical transmission decreased from
93% to 57% in the visible range. The hydrophobic silica films retained their hydrophobicity up to a
temperature of 250 8C 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) and contact angle measurements.