MECHANISM OF THE GRAFTING OF ORGANOSILANES ON MINERAL SURFACES .4. PHENYLDERIVATIVES OF SEPIOLITE AND POLY(ORGANOSILOXANES)

Grafting reactions of phenyl groups on silica substrates using as reagents various phenylsilanes with variable distances between the silicon atoms and the aromatic ring by 0, 1, and 2 methylene groups [= Si-(CH2)n-C6H5] were studied. Two different silicates have been selected as source of silica: sepiolite and tetraethyl-orthosilicate (TEOS). Sulfonic- and nitro-derivatives prepared from these phenyl compounds by electrophilic substitution reactions, have been obtained. The mechanism of these processes has been studied in relation to the number of methylene separating groups belonging to the starting reagents. The characterization of such systems has been achieved by XRD, Si-29 and C-13 NMR/MAS, IR, and laser microprobe mass spectrometry.