Synthesis of poly(styrene) monolayers attached to high surface area silica gels through self-assembled monolayers of azo initiators

We report on the radical-chain polymerization of styrene using self-assembled monolayers of azo initiators covalently bound to high surface area silica gels. In this process monolayers of poly(styrene) molecules terminally attached to the surface of the inorganic substrate are obtained. As the initiator molecules are immobilized at the surfaces in a one-step reaction, well-reproducible layers can be prepared and the surface concentration of the initiator can be adjusted in a wide range between the limit of detection and full surface coverage. In the subsequent polymerization reactions polymer monolayers with high, controlled graft density can be obtained. The synthesis of the attached layers and the characterization by X-ray photoelectron spectroscopy, diffuse reflectance infrared spectroscopy (DRIFT), and elemental analysis are described. After cleavage of an ester group that connects the polymers to the surface, the molecular weights of the polymers were determined. The results of the study show that this "grafting from" technique can be used for the preparation of polymer layers with controlled, high graft densities.