Preferential grafting of alkoxysilane coupling agents on the hydrophobic portion of the surface of micelle-templated silica

Silica having a regular mesoporous structure induced by micelle templating (MTS) was functionalised with n-propyltrimethoxysilane under anhydrous conditions. Support modification was characterised by various methods (X-ray diffraction, FTIR spectroscopy, thermogravimetry, nitrogen adsorption volumetry, microcalorimetry and FTIR of water adsorption). Functionalisation takes place mainly at the hydrophobic patches of the surface, involving surface siloxane bridges, and occurs through a nucleophilic displacement at the silicon atom by the alkylsiloxane group of the silylating agent. Hydrophilic patches of the surface, consisting of hydrogen-bonded silanol groups, do not constitute, in anhydrous conditions, active sites for the covalent anchorage of the organosilane moieties on the MTS surface.