Hydrophobic Material: Effect of Alkyl Chain Length on the Surface Roughness

Abstract

The clean technologies of self-cleaning surfaces are expanding rapidly. Highly hydrophobic coatings with strong adhesion, high durability, and dirt-free surfaces have been prepared via sol-gel deposition of SiO2-TiO2-alkylsilane. The influence of the effects of the alkyl chain length of silane on surface roughness was investigated. This deposition involved a one-layer technique to produce the rough surfaces. The bimetal oxide of SiO2-TiO2 created a high level of surface roughness. As a result, the water contact angle of the coatings increased with the increasing alkyl chain length of silane (up to C=8). However, the water contact angle decreased when the C=16 of alkylsilane was applied. It was predicted that the longer alkyl chain would cause the molecules to collapse. The higher hydrophobicity was produced by SiO2-TiO2-OTMS coatings with a water contact angle of about 140.67 ± 1.23°. The effect of the dip-coating technique (one layer and layer-by-layer) on hydrophobicity was also discussed. The results showed that coatings produced by the one-layer technique had a higher contact angle than coatings made by the layer-by-layer technique. The coatings were stable under outdoor exposure and able to hinder dirt attachment to their surfaces.

Keywords

• clean technologies
• self-cleaning
• hydrophobic
• alkyl chain length
• SiO₂-TiO₂-alkylsilane