EVERY school science student learns that plastics don鈥檛 conduct electricity,
but the astonishing discovery that some polymers can be made as conductive as
metals has earned three researchers this year鈥檚 Nobel Prize in Chemistry. 鈥淚t鈥檚
a very appropriate piece of work to have received a Nobel prize,鈥� says Richard
Friend of Cambridge University, who works with semiconducting plastics. 鈥淚t had
a huge impact on the chemistry and physics community.鈥�
Chemists Hideki Shirakawa and Alan MacDiarmid and physicist Alan Heeger were
working together in the 1970s at the University of Pennsylvania on polymers that
had a metallic glint. They modified one such plastic, polyacetylene, by blasting
it with iodine vapour, which gave it a positive charge. To their surprise, its
conductivity increased by a factor of 10 million. The modified polymer鈥檚
conductivity was a match for some metals, although it was still 2000 times less
conductive than copper.
The researchers realised that a polymer with alternating double and single
bonds along its chain of carbon atoms could be made to conduct electricity by
either adding or removing electrons. If you add an electron, it bumps the charge
along the chain from one carbon to the next, creating an electric current.
Removing an electron leaves a 鈥渉ole鈥� which can also bump along the chain
creating a current (New 杏吧原创, 5 March 1994, p 33). 鈥淚t seems
obvious now but it was really quite surprising then,鈥� says Friend.
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Researchers predict polymer-based electronics will soon become as ubiquitous
as silicon chips. 鈥淚 think we鈥檙e on the verge of a revolution in polymer
electronics,鈥� says Heeger. 鈥淧lastic electronics will be very low cost,鈥� he says,
making them ideal for use in high-volume applications.
Although conducting polymers marked the breakthrough, Friend says the action
has moved on. 鈥淭he emphasis now is on semiconducting plastics,鈥� he says.
Researchers have used these materials to make plastic transistors and LEDs,
heralding an era of cheap, robust displays that can be rolled up when not in
use. 鈥淚鈥檓 glad they won and put the focus on this field,鈥� says Ching Tang, a
chemist at Eastman Kodak in Rochester, New York.