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About conducting polymers.

We have been taught that plastics, unlike metals, do not conduct electricity. In fact plastic is used as insulation round the copper wires in ordinary electric cables.Yet the Nobel Laureates in Chemistry 2000 discovered in the late 70s that plastic can, after certain modifications, be made electrically conductive.

Medal

The Nobel Prize in Chemistry 2000

"for the discovery and development of conductive polymers"

 

Alan J. Heeger

Alan G. MacDiarmid

Hideki Shirakawa

Alan J. Heeger

Alan G. MacDiarmid

Hideki Shirakawa

University of California
Santa Barbara, CA, USA

University of Pennsylvania
Philadelphia, PA, USA

University of Tsukuba
Tokyo, Japan

Plastics are polymers, molecules that form long chains, repeating themselves like pearls in a necklace. In becoming electrically conductive, a polymer has to imitate a metal, that is, its electrons need to be free to move and not bound to the atoms. The first condition for this is that the polymer consists of alternating single and double bonds, called conjugated double bonds.However, it is not enough to have conjugated double bonds. To become electrically conductive, the plastic has to be disturbed - either by removing electrons from (oxidation), or inserting them into (reduction), the material. The process is known as doping.

The conductivities of the polymers vary considerably. Doped polyacetylene is, e.g., comparable to good conductors such as copper and silver, whereas in its original form it is a semiconductor.