Fabrication of transparent polysiloxane coatings on a glass support via the sol-gel dip coating technique and the effect of their hydrophobization with hexamethyldisilazane

This study aimed at synthesis, preparation, and physicochemical properties investigation of undoped polysiloxane-based coatings deposited on the glass supports. The other goal was to test the effectiveness of their hydrophobization with hexamethyldisilazane at an elevated temperature using a bubbler. The coatings were obtained in a sol-gel process by acid-assisted hydrolysis of tetraethoxysilane and they were applied to the glass supports using the dip coating technique with various withdrawal speeds. The synthesized composition was scanned using TurbiscanLAB and its particle size was determined by means of the dynamic light scattering technique. The obtained surfaces were examined based on the water wettability measurements, photoacoustic spectroscopy, and transmittance measurements. It was found that the stability of the sol did not change during the dip-coating. Smooth, homogeneous, uniform, hydrophobic, and transparent coatings on the glass supports were obtained. Their wettability was determined by the contact angle in the range from 83.5 to 95.2 degrees and very low contact angle hysteresis. The hydrophobic effect obtained by modification with hexamethyldisilazane appears to be permanent – the contact angles do not change significantly after 7 days. The synthesized sol composition appears to be a good starting point for its chemical and physical modification for hydrophobicity increase and surface properties modification. Moreover, the hydrophobization of the coatings with hexamethyldisilazane at an elevated temperature using the bubbler did not have the desired effect.