Photochemical attachment of polymer films to solid surfaces via monolayers of benzophenone derivatives

We report a simple and yet effective way to photochemically attach thin polymeric layers to solid surfaces. The system is based on a photoreactive benzophenone derivative that is bound to SiO2 surfaces via a silane anchor. This substrate is then covered with a polymer film that is reacted with the benzophenone moieties by illumination with UV light (lambda > 340 nm). As a result of the photochemical reaction, a thin layer of the polymer is covalently bound to the surface. Nonattached polymer is removed by extraction. As examples, we have successfully attached thin layers of poly(styrene) and poly(ethyloxazoline). The thickness of the layer is a function of the illumination time and the molecular weight of the polymer. The film thickness increases linearly with the radius of gyration of the polymers used for attachment. Using this system, we were able to photochemically attach up to 16 nm thick films of poly(styrene).