Synthesis and Characterization of New Organic–Inorganic Hybrid Nanosilica Fillers Prepared by Sol–Gel Reaction

In light of the success of making multicomponent sol–gel glasses, in this study the synthesis of new hybrid nanosilicas with controlled hydrophilic/hydrophobic properties was carried out by incorporating organic based species with appropriate functional groups to inorganic based alkoxides by co-condensation reaction. Furthermore, in this study the acidity and the water content during reaction synthesis was proven to be critical in controlling the structure of the hybrid nanosilicas. These nanosilicas with different hydrophobicity were obtained by using TEOS (tetraethylorthosilicate) and 10 wt% two organic modifiers (tris-hydroxymethylaminomethane — TRIS — and 1,1,1,3,3,3-hexamethyldisilazane-HDMS). The average diameter of the nano-particles ranged between 7 and 10 nm. The addition of the organic modifiers changed the pH of the hybrid nanosilicas, to a different extent depending on the nature of the organic modifier. The hydrophobicity in the hybrid nanosilicas estimated from pH measurements in water and ethanol, and from IR spectroscopy, can be tailored by incorporating different organic modifiers on the network during synthesis. Finally, the measurement of pH of the hybrid nanosilicas by using solvents with different polarity/acidity was a simple and efficient method of assessing the hydrophobicity of the nanosilicas.