Silylation

Polymer and Separations Research Laboratory (PolySep)

This area of investigation focuses on anhydrous silylation of multi-alkoxy silanes onto inorganic oxide surfaces. In recent work, the silylation of vinyl trimethoxysilane (VTMS) onto silica and zirconia substrates was investigated experimentally to demonstrate and quantify the effects of surface water on multilayer silylation. Silylation coverage was controlled by the availability of surface water, which is consumed in multilayer silylation reactions. We found that silylation coverage increased with surface water coverage, reaching a maximum at approximately two monolayers of water. Subsequent decline in silylation coverage is attributed to the formation of bulk polysilanes and decreased accessibility of the water-bearing surface to the hydrophobic VTMS molecules. In the region past the maximum silylation coverage, the silylation efficiency is significantly reduced which is attributed, in part, to the formation of polysilanes and thus reduced surface attachment due to steric effects. In this region there is a need for a theory which accounts for bulk polysilane formation.

AFM images of surfaces with with multi-alkoxy silanes coverage revealed nanometer scale cluster-like surface morphology consistent with the formation of bonded polysilanes.
A close-in view of the surface (see above) shows nearly complete surface coverage. These clusters can be viewed upon magnification as seen in the Figure below
The present study suggests that multilayered silylated surfaces can be prepared reproducibly. Such surfaces could prove useful in applications that require high concentration of surface active groups such as in ceramic membrane modification, construction of biocompatible surfaces and adhesion enhancement in polymer composites.

Reference

Yoshida, W, Castro, R. P., Jou, J. D. and Cohen, Y., "Multilayer alkoxysilane silylation of oxide Surfaces," Langmuir, 17, 5882-5888 (2001).
Cohen, Y., R. Faibish and M. Rovira, Size Exclusion Chromatography with Graft Polymerized Silica Resins, in "Surface Interactions in Size Exclusion Chromatography, " E. Pefferkorn (Editor) Marcel Dekker, (1999).
Chaimberg, M. and Y. Cohen, "Silylation of Inorganic Oxide Supports," J.Colloid.Interface.Sci, 134, 576-579 (1990).
Publications

Last update:

10/23/2004