Functionalized silicas are widely used in composite materials, as catalysts, and in many other applications. A detailed knowledge of the mechanisms and kinetics of the reactions required to create these surface functionalized materials is often not available. These issues are not readily addressed using high surface area amorphous silicas. An approach using a solution soluble silsesquioxane mono silanol compound is presented. The silsesquioxane is reacted with 3-aminopropyldimethylmethoxysilane to mimic an important class of reactions to create surface modified silicas with functionalized amino groups.

Kinetics data is obtained using solution FTIR spectroscopy by analyzing the loss of the SiO-H group over time. The excellent overall second order fit to the data indicates that the amine functionality catalyzes the silylation reaction via intramolecular rather than intermolecular catalysis. Rate constant data as a function of temperature shows that at room temperature and higher the rate constant decreases with increasing temperature. Implications of these surprising results are discussed and further analyzed. Data on the role of solvent on the kinetics are also presented both for the silsesquioxane model compound and for nanoparticulate fumed silica surface reactions. These studies provide a new level of insight into these industrially important reactions for materials synthesis. Implications of these results from both fundamental and applied materials synthesis viewpoints are discussed.