Hydrophobic properties of hexamethyldisilazane modified nanostructured silica films on glass: effect of plasma pre-treatment of glass and polycondensation features

Effects of pre-treating the surface by oxygen and argon plasma, conditions of the sol-gel synthesis of hydrophobic films and modification by silica nanoparticles were studied for two types of sol-gel compositions resulting in coatings of different topology. Wetting study and profilometry were used for characterization of the films hydrophobicity and surface roughness. It was shown that the variation in the amount of acid in the reaction mixture significantly affects the hydrophobicity of the synthesized films due to changing the surface texture upon interactions with HMDS. For the series of films produced at high acid contents, the contact angle (CA) with water is 91.67°–98.98° while reducing the amount of acid allows to obtain films with the CA of 127.88°–132.68°. Modifying films with the silica nanoparticles can further increase hydrophobicity of the obtained films by the influence on their topography. Pre-treatment of the glass surface by air and argon plasma has a significant impact on the structure of the glass, however a significant effect on hydrophobicity of the applied film is not observed.