Non-fluorinated superamphiphobic surfaces through sol–gel processing of methyltriethoxysilane and tetraethoxysilane

In this study, a simple approach was developed to fabricate an extremely superamphiphobic coating material by the tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) sol–gel derived materials. TEOS and MTES derived moieties were designed for a physical roughness and hydrophobic surface characteristic, respectively. The 29Si solid-state NMR and ESCA analysis showed the coated silica composition was similar to the feeding ratios of TEOS/MTES. The surface structure characterized from SEM and TEM suggested the nanoparticle-based silica surface was observed at a high TEOS/MTES content but changed to a relatively smooth surface at a low TEOS content. The contact angles of water and CH2I2 on the pure TEOS derived coated surface were both 0° due to the hydrophilic Si–OH group. As the MTES composition increased to 25 mol% (T5M3), the coated surface had the contact angles of 149.8° and 133.1° for water and CH2I2, respectively. It revealed that the T5M3-coated surface exhibited both super-hydrophobicity and super-oleophobicity, i.e., superamphiphobicity. Also, it had a relatively low-surface energy (1.38 mJ m−2) considerably lower than that of the F-silane-coated surface with 39.3 mJ m−2. As the MTES composition increased further, both contact angles of water and CH2I2 decreased. Especially, they decreased dramatically at the MTES feeding composition higher than 75 mol%, due to the much less rough surface at a higher MTES composition. The present study suggests that superamphiphobic surface could be achieved by non-fluorinated sol–gel derived silica materials.