Non-wettable surfaces with high contact angles and facile sliding angle of water droplets have received
tremendous attention in recent years. The present paper describes the room temperature (27 8C)
synthesis of dip coated water repellent silica coatings on glass substrates using iso-butyltrimethoxysilane
(iso-BTMS) as a co-precursor. Emphasis is given to the influence of the hydrophobic reagent (iso-
BTMS) on the water repellent properties of the silica films. Silica sol was prepared by keeping the molar
ratio of tetraethoxysilane (TEOS) precursor, methanol (MeOH) solvent, water (H2O) constant at
1:16.53:8.26 respectively, with 0.01 M NH4F throughout the experiment and the molar ratio of iso-
BTMS/TEOS (M) was varied from 0 to 0.965. The effect of M on the surface structure and hydrophobicity
has been researched. The static water contact angle values of the silica films increased from 658 to 1408
and water sliding angle values decreased from 428 to 168 with an increase in theMvalue from 0 to 0.965.
The water repellent silica films are thermally stable up to a temperature of 280 8C and above this
temperature the film shows hydrophilic behavior. The water repellent silica films were characterized by
the Fourier TransformInfrared (FT-IR) Spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force
Microscopy (AFM), % of optical transmission, thermal and chemical aging tests, humidity tests, static and
dynamic water contact angle measurements.