Scientists are envious of nature

Clicking and voltage are the basics for the method to copy a part of mother natures ability of using signal molecules Source: Quelle: Wiley-VCH

It takes a great deal of effort for scientists to produce defined microscale structures. Pierre Schaaf and a team of scientists from Strasbourg have now imitated a few of nature’s tricks in order to get a polymer film to "grow" onto a surface. As the researchers report in the journal Angewandte Chemie International Edition 2011, 50, No. 19, pages 43744377, they used morphogens as nature does. These signal molecules show a reaction which way it should go. Schaaf and his co-workers formed thin films on a substrate using a sort of morphogen to steer the process. The reactants involved were polymers, one containing azide groups and the other with alkyne groups as side chains. In the presence of positively charged copper ions (CuI), these groups react with each other to form a carbon- and nitrogen-containing five-membered ring, crosslinking the polymers. This type of reaction is called "click chemistry", because the reaction partners simply snap together. The scientists’ idea was thus to place the CuI ions as a morphogen only on the surface to be coated. Their approach was to place CuII ions in the solution. They then applied an electric voltage to the surface. When CuII ions come into contact with this surface, they take an electron to become CuI. These are thus primarily to be found on the surface. Where there are CuI ions, the click reaction can proceed; the polymers only crosslink into a continuous film on the surface. The magnitude of the applied voltage can be used to control the number of CuI ions and thus the thickness of the film.