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Plastic Is Electrifying!
| Article
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10559 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
1 / 1993 |
2,567 Words |
| Author
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Hank Hogan
Hank Hogan is a science writer in Austin, Texas. |
Amid all the hoopla surrounding the gains being made in superconductivity, another relatively new type of material has been over shadowed. As a conductor of electricity, this new material promises to be lighter in weight than copper. What is more, this new material can also act like a semiconductor and therefore is a potential replacement in some applications for silicon or gallium arsenide. I addition, this new material can be formed into thin, flexible, transparent sheets that emit light or change color easily.
Just what is this new "super" material? It is plastic, but not the same plastic, that's wrapped around wiring every day precisely because it does not conduct. Instead, it is a new and different type of plastic, one that is a conductor and not an insulator.
Alan Heeger, a professor of materials and physics at the University of California at Santa Barbara, comments, "You have a new class of materials with a unique combination of properties. You have the electrical and optical properties of metals and semiconductors and you also have the mechanical advantages and processing advantages of polymers [plastics]."
Synthetic metals
The discovery of conducting plastics, or polymers, dates back to the mid-1970s. At that time the search for conducting polymers had just begun, but there was a theory already in place to guide that search.
The theory depended upon the basic nature of plastic, a generic term that covers a wide range of polymers, materials whose constituent molecules are long chains of repeating small molecular building blocks called monomers. Electrons are essential actors in the bonding through which monomers form polymers, just as electrons are essential actors in electrical conductivity. There surely are plenty of electrons in the polymer, yet polymers in general do not conduct electricity.
"There are electrons in the insulating polymer, but there's no space for them to move around in," notes Arthur Epstein, a physics and chemistry professor at Ohio State University who has worked in the area of conducting plastics for 20 years.
The key, then, to transforming an insulator into a conductor is to make some space for the electrons to move around in.
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