Figure: Functional polymer brush

Figure: Example of a methacrylate based polymerbrush carrying a NHS ester group

Functional Polymer Brushes

Functional brushes are polymer monolayers in which the macromolecules carry functional groups that can be used for subsequent reactions or as sensor units. Groups of interest are for example:

• DNA strands
• proteins
• complexing agents
• dyes
• photoreactive compounds
• other polymers or oligomers

Again, we typically use the "grafting from" technique to synthesize such architectures on the surfaces. In order to create functionalities on a surface one can of course use monomers that carry such groups and form the layer directly. However, in many cases such monomers may not be available in sufficient amounts if at all. Additionally, each new monomer would make it necessary to firstly study the behavior of this monomer during polymerization. Finally, the free radical polymerization process that is used to create the polymers does not tolerate all possible functionalities that might be interesting. Thiol groups, for example, exhibit very high transfer constants. Such processes would deminish the molecular weight of the attached chains to an extent that is not acceptable. Based on these considerations, we decided to chose an alternative route and to use a monomer with a functionality which can be transformed into the desired function after the preparation of the polymer monolayer. Many molecules that are interesting as sensor units are available as amines and therefore we often use a monomer that carries a group that reacts specifically with amines. N-hydroxysuccinimide esters are suitable candidates for this purpose.