Robust hydrophobic coating on glass surface by an atmospheric-pressure plasma jet for plasma-polymerisation of hexamethyldisiloxane conjugated with (3-aminopropyl) triethoxysilane

Plasma polymerisation of hexamethyldisiloxane (HMDSO) and (3-aminopropyl)triethoxysilane (APTES) was attempted to form a robust hydrophobic coating film on glass surface. Although HMDSO is a common precursor for generating hydrophobic surface, the HMDSO-polymerised thin film is poor in strength. For the purpose of achieving the mechanical robustness of the coating, APTES was used together with HMDSO. Plasma polymerisation was performed using a dielectric barrier discharge plasma jet by varying the ratio of the two precursors to find a suitable condition that would produce robust hydrophobic thin film. Various instrumental techniques were used to characterise the coating layer. As a result of the examination of the hydrophobicity through the water contact angle measurements and the robustness by the scratch tests, the most reasonable coating was achieved at the HMDSO/APTES ratio of 3/1, the voltage of 7 kV and the treatment time of 60 s, and at this condition the WCA was 143°.