The Nobel Prize in Chemistry was awarded yesterday
to three scientists who created a plastic that conducts electricity like
a metal, a discovery that has opened up a new field of carbon-based electronics.
The prize of about $913,000 will be shared by Dr. Alan J. Heeger, 64,
of the University of California at Santa Barbara; Dr. Alan G. MacDiarmid,
73, of the University of Pennsylvania; and Dr. Hideki Shirakawa, 64, of
the University of Tsukuba in Japan.
The technology is already used to make antistatic coating on photographic
film and is expected over the next few years to find its way to bright,
low-energy displays in cell phones and other hand-held electronics.
''I thought this was a very nice recognition for the field,'' said Dr.
MacDiarmid, a native of New Zealand.
Plastics are made of an entwined mesh of long molecules called polymers,
each with a central strand of carbon atoms. Polymers generally do not conduct
electricity, which is why metal wires are wrapped with plastic insulating
sheaths to prevent short circuits.
Illustrating the sometimes serendipitous path of science, the discovery
of plastic conductors began with a mistake and was nudged forward by an
opportune coffee break.
In the early 1970's, Dr. Shirakawa developed a technique for producing
thin films of the polymer polyacetylene. One day, a researcher in his laboratory
misheard his instructions and added 1,000 times too much catalyst to the
chemical reaction. The result was a silvery film composed of a different
form of polyacetylene.
Meanwhile, Dr. MacDiarmid and Dr. Heeger, then
also at Penn, had made a metallic-looking film out of strands of sulfur
nitride. Dr. MacDiarmid mentioned the sulfur nitride film during a seminar
in Tokyo. Dr. Shirakawa met Dr. MacDiarmid during the coffee break and
told him about the silvery polyacetylene film.
Curious, Dr. MacDiarmid invited Dr. Shirakawa to Penn, where the researchers
diffused iodine into Dr. Shirakawa's polyacetylene films -- a hunch based
on their experience with sulfur nitride.
''The iodine then pulls some of the electrons out of the plastic and
therefore the remaining electrons are not packed so tightly,'' Dr. MacDiarmid
said. ''Then the electrons can move more easily from one electrode to another.''
The effect was quickly apparent.
''The electrical conductivity increased by a factor of 10 million in
a few minutes,'' Dr. Heeger recalled, ''and we knew we were onto something.''
Dr. Arthur Epstein, a professor of chemistry at Ohio State University,
recalled his astonishment when the findings were presented at a 1977 conference
in New York City.
Before then, ''plastics were known as materials that did not conduct
electricity,'' he said. The discovery, he said, ''opens up the use of organic
chemistry for the development of metals and semiconductors.''
The Royal Swedish Academy of Sciences, which administers the Nobel Prizes,
wrote, ''The choice is motivated by the important scientific position that
the field has achieved and the consequences in terms of practical applications
and of interdisciplinary development between chemistry and physics.''
While polyacetylene itself is not very useful, its creation spurred
chemists around the world to craft other new polymers that behave like
metals or semiconductors.
''It's spawned a small industry,'' said Dr. Lewis J. Rothberg, a professor
of chemistry at the University of Rochester. ''There are many thousands
of us working in this general area now.''
Plastic semiconductors do not perform as well as silicon and will not
replace silicon in computer chips. But plastic has other important advantages:
It is light, cheap, flexible, and easy to shape, qualities that open up
new applications. Agfa, for instance, adds a layer of conducting polymers
to its photographic film to drain away static charge that might otherwise
ruin the film.
Scientists at Cambridge University made polymers that can emit light,
which will soon be used for low-cost, low-energy, possibly even foldable
video displays. The research on conducting polymers also has applications
in the emerging field of molecular electronics, where transistors and other
components will be fashioned out of individual molecules.
In 1990, Dr. Heeger founded a company, Uniax, to make and sell conducting
polymers. Dr. Heeger sold the company to DuPont earlier this year.
Organizations mentioned in this article:
Swedish Academy
Related Terms:
Chemistry; Nobel Prizes; Awards, Decorations and Honors; Plastics;
Electronics; Biographical Information
