The surprising discovery that plastics can be made to conduct electricity as easily as a metal earned three scientists this year鈥檚 Nobel Prize in Chemistry.
The Japanese chemist Hideki Shirakawa, the American chemist Alan MacDiarmid and the American physicist Alan Heeger will share the 拢625,000 prize for their work with polyacetylene in the 1970s.
They were able to boost the conductivity of the polymer by a factor of 10 million, making it as conductive as some metals 鈥� though still about 2000 times less conductive than copper.
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鈥淚t鈥檚 a very appropriate piece of work to have received a Nobel prize,鈥� says Richard Friend, a physicist at the University of Cambridge who works with semiconductive plastics and has a business in the field. 鈥淚t had a huge impact on the chemistry and physics community.鈥�
Conductive polymers are now being used in 鈥渕olecular electronics鈥�, helping to make tiny, plastic component parts for computers.
Some find the prize a little surprising, since most of the technological applications for the field now involve semiconductive plastics, a slightly different field whose origins aren鈥檛 really dependent on the discovery of conductive polymers. 鈥淚 don鈥檛 think they set the stage for the revolution,鈥� says Ching Tang, a chemist at Eastman Kodak in Rochester, New York.
The prizewinning researchers modified the polyacetylene by blasting it with iodine vapour. This removed an electron, giving it a positive charge, and had the unexpected effect of massively increasing its conductivity.
The graduate student who actually made the measurement 鈥渨as very sheepish鈥�, laughs Heeger. 鈥淭he instruments he was using had burnt out [from the high reading] and he was very apologetic. I wasn鈥檛 sad at all.鈥�
They realised that organic polymers with alternating double and single bonds could be made to conduct electricity by either adding or removing electrons. This process is called 鈥渄oping鈥�, by analogy with the way devices such as transistors are made.
Most applications of semiconducting polymers depend on the fact that plastics are cheap and easy to manufacture. 鈥淧lastic electronics will be very low cost,鈥� Heeger says, making them ideal for use in high volume applications.