Electrons turn red polymers green

A polymeric material that changes colour when an electric current is applied has been developed by scientists in Germany.

The polymer, known as a metalloviologen, is made from cobalt ions and a nitrogen-containing organic compound. Dirk Kurth and colleagues from the Max Planck Institute of Colloids and Interfaces in Potsdam used the compound to build up a film layer-by-layer using electrostatic self-assembly.

The film acts as an electrochromic component, turning from red to green when electrons are added to the polymer. The original red colour is restored when the electrons are removed.

This is the first example of a metalloviologen being incorporated in an operating device.

Metalloviologens' potential lies in their use as molecular materials. It is easy to change their properties, for example their colour, by changing their metal ion. Materials like this could be used to coat windows, allowing information to be displayed at the touch of a button.

Lorna Jack