Surface-attached polymer networks

Schematic representation of a surface-attached polymer network.

Surface-attached polymer networks are interfacial architectures in which thin films of polymers are not only crosslinked but also chemically linked to the underlying surface. Such layers are interesting in many ways as the chemical anchoring of the films to the surfaces ensures excellent adhesion of the layers even when they are used in solvents that lead to a strong swelling of the layers.

Layers or microstructures of these networks may consequently be used as sensors by adding probe functionalities within the film. The probes are then presented to an analyte solution in a somewhat three-dimensional fashion which allows for an enhanced probe density as compared to an strictly 2D arrangement on a surface.

One essential part of our research in that regard is the development of synthetic strategies for the generation of surface-attached networks. Here, we focus our work especially on the synthesis of monomeric curing agents which can be copolymerized with conventional monomers. In all cases we use C,H insertion reactions to generate the crosslinks and the attachment sites to the surface. This general strategy is shown in Figure 1b and compared to the more usual approach via bifunctional components. The advantage of C,H insertions is - among others - that an attachment to polymeric surfaces is often possible without the need for any functionalization of the substrate.

Figure 1: Schematic discription of a) crosslinking of reactive polymers via bifunctional coupling and b) via C,H insertion reactions. The latter approach does not require matching functional units.

There are many different suitable reactive units for C,H insertions. Many of those are photoreactive others can also be triggered thermally. We develop a tool box that provides groups appropriate for different needs as they may arise from certain applications. Figure 2 summarizes the most frequently used reactiv units at CPI.

Figure 2: Reactive units for C,H insertion reactions to generate
surface-attached polymer networks.