THE ROLE OF SILANOLS IN THE MODIFICATION OF SILICA-GEL WITH AMINOSILANES

In the modification of silica gel with aminoalkoxysilanes, silanols ar e present on the substrate surface and, after hydrolysis, in the silan e molecule, The manner in which both types of silanols participate in the modification mechanism is elucidated, using nuclear magnetic reson ance (NMR) and Fourier transform infrared (FTIR) spectroscopic techniq ues. Deuterium exchange of surface hydroxyls before silanation is used in order to distinguish initial surface silanols from those created i n the course of the modification, Surface hydroxyls are the active sit es for the bonding of coating molecules. Small patches of unreacted hy droxyls remain after modification. An FTIR peak at 3731 cm(-1) is assi gned to silane silanols, which are stable at low silane surface loadin gs. (C) 1995 Academic Press, Inc.