Electricity turns plastic green

Red, green and blue are the important colors in electronics -- any other color can be made by mixing these three.

Electrochromic polymers change color -- meaning they reflect a different mix of light wavelengths -- in the presence of an electric field. It is relatively easy to make red and blue electrochromic polymers because those colors each involve a single band of wavelengths. Green is more difficult, however, because it involves two different regions of the visible spectrum.

Researchers from the University of California at Los Angeles have made a conducting polymer that changes to a very clean green color in the presence of electricity. To do so, the researchers had to design a polymer molecule that had two independent chromophores, which are areas that absorb different regions of the visible light spectrum.

Eventually red, blue and green electrochromic polymers could be used to make simple, inexpensive and flexible displays.

The researchers' prototype switches colors quickly and also proved very stable, according to the researchers.

Some work remains to make the polymer suitable for practical use, however. The polymer would have to reflect a different primary color when the electricity is off. The current prototype changes from primary green to a brownish yellow rather than blue or red.

The work appeared in the March 12, 2004 issue of Angewandte Chemie International Edition.