Synthesis of Coupling Agents for the Surface Grafting of Polymers

The modification of surfaces firstly asks for suitable molecules that can be reacted with groups on the surface on the one hand and that carry further functions for subsequent reaction steps if desired. The group necessary for surface attachment is usually determined by the chemical nature of the substrate. In surface science there are two major types of substrates that are used very frequently: SiO₂ surfaces (glass, quartz, silicon wafers, evaporated or sputtered layers) because they can be readily modified and gold surfaces because they are reasonably flat and very stable against corrosive influences. Glass and other SiO₂ surfaces are best modified by silanes, especially chloro silanes (see image) and there is a vast amount of different compounds that are commercially available. The functionality (F) at the other end of the coupling agent is needed for further reactions. In our case - we want to modify surfaces with polymer molecules - this group must be either capable of binding to appropriate groups of these macromolecules or it must be an initiating group, i.e. a site from which a polymer chain can be grown. We have synthesized a variety of molecules for both cases and the shown on this page show some of our most prominent compounds. The silane 1 is an example for radical chain initiators for the growth of polymers at surfaces in situ; compound 2 is useful to photochemically immobilize off-the-shelf polymers but also to grow polymers by photoinitiation. Compound 3 is again a radical chain initiator specifically designed for photopolymerizations at surfaces.