The effect of methyltriethoxysilane (MTES) concentration on hydrophobic properties of silica thin layer

One of the hydrophobic materials is silica thin layer in which a hydrophobic silica precursor is superimposed on the material surface that makes it hydrophobic. Methyltriethoxysilane (MTES) is a favorable hydrophobic silica precursor because it has a methyl group that functions as a hydrophobicity guiding agent. In this study, the synthesis of thin layer and hydrophobic silica xerogel from MTES using the sol-gel method with ethanol-ammonium hydroxide solvent was carried out. The MTES concentration was varied to 1.42, 2.85, 5.70, 11.40, and 22.80 M to assess the effect of MTES concentration on the hydrophobic nature of the silica thin layer. The MTES solution was coated on the glass surface with a dip-coating method to measure the contact angle then. Xerogel preparation was carried out by drying the MTES solution at room temperature. It continued by drying in an oven at 60°C for 2 hours then calcined at 300°C. The xerogel generated were analyzed using FTIR. It was found that the variation of MTES concentration had a considerable effect on the hydrophobic nature of the silica thin layer. Increased MTES concentration, from a concentration of 1.425 M to 11.4 M, escalated the contact angle of silica thin layers. The highest contact angle was achieved at MTES concentration of 11.4 M and calcination temperature of 300 °C, which reached 82.53°. Nevertheless, the thin layer produced was still hydrophilic, which was characterized by the contact angles of less than 90°, and the Si-OH/Si-O-Si ratio increased.