Abstract

The compounds N 3P 3[NH(CH 2) 3Si(OEt) 3] 6 (1), N 3P 3[NH(CH 2) 3Si(OEt) 3] 3[NCH 3(CH 2) 3CN] 3 (2) and N 3P 3[NH(CH 2) 3Si(OEt) 3] 3 [HOC 6H 4(CH 2)CN] 3 (3) undergo slow gelation at the interface oil/air at low temperatures to give perfect gels G 1, G 2 and G 3 respectively. TEM analysis reveals nanoparticles of silica with mean size of about 10 nm. Pyrolysis under air at 800 °C of these gels affords a mixture of mainly Si 5(PO 4) 6O, SiP 2O 7 and SiO 2. Gelation and pyrolysis products were characterized by IR, solid-state NMR, TEM, SEM-EDAX microscopy and X-ray diffraction. The sol-gel process in the interface liquid /air is discussed in comparison with the usual sol-gel solution process.