The covalent attachment of polymers such as polystyrene, polymethylmethacrylate and polyacrylonitrile to microparticulate silica and to silicon wafers through immobilized radical chain initiators (especially azocompounds) is described. The initiator is bonded to the surface using α,ω-substituted silanes, which have only one functional group at the silane head group.
Up to 10 g of polymer per g of silica could be covalently bonded to the surface. The attached monolayers were characterized using diffuse reflectance FTIR spectroscopy, XPS and elemental analysis. After the cleaving off of the attached layers molecular weights up to 300.000 g/mol were measured. Transmission electron micrographs generated with an element specific imaging technique (ESI) clearly show a continuous, about 10 nm thick, polymer layer around the silica particles.