Surface functionalization with phosphazene substrates. Part I: Silica and Si-(100) surface functionalization with cyclophosphazenes partially substitued with trialkoxysilane derivatives and 4-cyanophenol as a marker molecole

In this paper we report the utilization of phosphazene substrates for the surface function-alization of silicon-based materials (e.g., silica gel beads and crystalline silicon(100) wafers) and for the preparation of monoliths by means of a sol-gel technique. We used multifunctional cyclophos-phazenes to prepare trimers substituted with equimolecular amounts of ?-aminopropyltriethoxysilane and 4-cyanophenol. The first substituent was used to attach the phosphazene materials to the surface of the silicon-based substrates by reaction of the triethoxysilane functions with the free hydroxylic groups present on the surface of the silica gel particles or of the crystalline silicon wafers. Further-more, the second substituent, i.e., 4-cyanophenol, was exploited as an internal marker, because of the presence of a peculiar band at 2230 cm-1 in its IR spectrum, to reveal the presence of the cyclophosphazene on the surface of the functionalized substrates. This approach is completely general and can be used very easily to induce specific modifications on the surface of different materials by carefully selecting the substituent groups inserted in the cyclophosphazene substrate.