Surface modification of SiO₂-based methyltrimethoxysilane (MTMS) using cetyltrimethyl ammonium bromide (CTAB) on the wettability effects through hierarchical structure

Abstract: Silica-based methyltrimethoxysilane (MTMS) offers unique properties as an alternative material for hydrophobic surfaces. In this study, SiO₂ obtained through the MTMS precursor with various concentrations of cetyltrimethylammonium bromide (CTAB) 0.75 wt%, 1.5 wt%, and 2.25 wt% were prepared by sol-gel method to modify and improve a hydrophobic surface. With the addition of CTAB, particle sizes are more extensive, and peak diffractions shift to a lower angle according to scanning electron microscope (SEM) images and X-ray diffraction (XRD), respectively. Fourier transform infrared (FTIR) demonstrated Si-O-Si asymmetric stretching bonds. Then, the samples were coated on steel plate substrates by the dip-coating method. Based on atomic force microscope (AFM) analysis, surface roughness was larger because of the presence of CTAB. Furthermore, water contact angle (WCA) was measured to characterize hydrophobicity using distilled, deionized, and seawater media. The WCA of the samples was more significant with the increase of CTAB content. The sample dropped to seawater medium possesses the largest WCA with a magnitude of 126.1 ± 0.8°. Because the samples with CTAB content coated on steel plate substrates own hydrophobicity, they are useful for drag reduction application on the ship’s hull coating. Graphical Abstract: [Figure not available: see fulltext.]