[Sitemap] [Contact] [Imprint] Deutsche Version Search site 


Published: 03.05.2011

Polymer Films by Click Chemistry

Signpost for chemical snaps: copper ions as morphogens for the formation of polymer films by click chemistry.

Scientists are envious of nature because of its ability to build up highly complex structures like organs and tissues in an ordered fashion without any problem; 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, they used morphogens as nature does. These signal molecules show a reaction which way it should go.

Polymers that 'click'

Polymers that 'click': A polymer film is obtained by the Cu(I)-catalyzed Sharpless click reaction between two polymers, bearing either azide or alkyne groups, both present simultaneously in a Cu(II) solution (see picture). The Cu(I) morphogen is generated at an electrode by applying an adequate potential. This concept can be extended to supramolecular films formed by coordination complexes.

[Credit: Angewandte Chemie International Edition]

The growth of our bones, seashells, or the complicated forms of diatoms, requires the processes involved in biomineralization to occur along precisely controlled tracks. Molecules cannot simply be allowed to react in an uncontrolled fashion as soon as they encounter each other. In order for a complex organism to develop, every individual cell must know where it is located within a growing organ. Special signal molecules called morphogens inform the cell. They are formed in a specific location and then spread out into the surrounding tissue. This results in concentration gradients, which the cells can use to “orient” themselves.

Schaaf and his co-workers chose a similar strategy to form thin films on a substrate. They also used a sort of morphogen to steer the process. The reactants involved were polymers, one containing azide groups (–N3) and the other with alkyne groups (–C=CH) 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.

In a solution containing both click partner and CuI ions, the reaction would immediately proceed at random. This would not result in a thin polymer film. The scientists’ idea was thus to place the Cu(I) ions as a morphogen only on the surface to be coated. Their approach was to place Cu(II) ions in the solution. They then applied an electric voltage to the surface. When Cu(II) ions come into contact with this surface, they take an electron to become Cu(I). These are thus primarily to be found on the surface. Where there are Cu(I) 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 Cu(I) ions and thus the thickness of the film.


Further Information and Source:
Gaulthier Rydzek, Dr. Loïc Jierry, Dr. Audrey Parat, Dr. Jean-Sébastien Thomann, Dr. Jean-Claude Voegel, Dr. Bernard Senger, Dr. Joseph Hemmerlé, Dr. Arnaud Ponche, Dr. Benoît Frisch, Prof. Pierre Schaaf, Dr. Fouzia Boulmedais:
Electrochemically Triggered Assembly of Films: A One-Pot Morphogen-Driven Buildup.
In: Angewandte Chemie International Edition; volume 50, issue 19, pages 4374-4377, May 2, 2011
DOI: 10.1002/anie.201007436
URL: direct link
Pierre Schaaf, Institut Charles Sadron, Strasbourg, France
Source: Angewandte Chemie International Edition, press release 17/2011
Related Information:
Publish your Press Release ...
More on the topic (background information, research articles, etc.): See top left menu bar!

Chemistry information not found? Try this form:
Custom Search

Internetchemistry ChemLin © 1996 - 2013 A. J. - last update 03.05.2011