Super Hydrophobic Mesoporous Silica with Anchored Methyl Groups on the Surface by a One-Step Synthesis without Surfactant Template

Abstract

Mesoporous silicas with methyl groups anchored on the pore wall by covalent bonds were prepared using polymethylhydrosiloxane and tetraethylorthosilicate as silica sources via a one-step synthesis approach. No surfactants were introduced in the synthesis and the pore size can be tuned readily by adjusting the amount of polymethylhydrosiloxane used in the synthesis. Generally, such a hybrid structure is achieved by two steps: synthesizing mesoporous silica substrate using surfactant as template and grafting the pore wall surface with an organic silane. The synthesis in this study is based on a nonsurfactant route and thus is distinctly different from other synthesis routes in reaction mechanism. The obtained silicas exhibit superior hydrophobicity: their contact angles with water are all beyond 150 degrees because the surface is covered by methyl groups. The hydrophobic silicas can be used as efficient adsorbents for cleaning up spills of oil or organic chemicals on the water surface and toxic organic pollutants in water, such as alkylphenols, at very low concentrations.