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 cond itions. Support modification was characterised by various methods (X-ray di ffraction, FTIR spectroscopy, thermogravimetry, nitrogen adsorption volumet ry, 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 sil icon atom by the alkylsiloxane group of the silylating agent. Hydrophilic p atches of the surface, consisting of hydrogen-bonded silanol groups, do not constitute, in anhydrous conditions, active sites for the covalent anchora ge of the organosilane moieties on the MTS surface.