Octadecylsilane hybrid silicas prepared by the sol–gel method: Morphological and textural aspects

A series of octadecylsilane-modified silicas was prepared by the sol–gel method through the hydrolysis and cocondensation of tetraethylorthosilicate (TEOS) with octadecyltriethoxysilane (ODS). The ODS:TEOS ratio was varied between 0:100 and 100:0. The resulting carbon content was between 2.5 and 53.4%. In the case of pure ODS, the resulting silica presented 68.6% of C. Hybrid silicas were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and 29Si nuclear magnetic resonance spectroscopy. Spheres of ca. 0.5–1.0 μm were obtained in the case of hydrolysis of pure TEOS. The combination of ODS:TEOS ratio yielded systems combining spherical and lamellar patterns zones. Monitoring the particle growth, it seems that spherical particles grow around lamellar zones, these latter concentrating the organosilicon moieties. The degree of cross-linking of ODS moieties was shown to be dependent on the ODS addition time and stirring speed.

The effect of TEOS/ODS ratio, of the addition time and stirring speed on surface coverage, and on morphological and textural characteristics of the resulting hybrid materials was evaluated. Hybrid silica changed from totally spherical morphology to lamellar domains as the ODS amount was increased.Figure optionsDownload as PowerPoint slide