ELECTRONIC POLYMERS COULD ONE DAY REPLACE COPPER
COLUMBUS, Ohio -- Researchers at Ohio State University have found a way to increase the conductivity of electronic polymers to such a degree that they could one day replace copper as the most commonly used electrical conductor.
Electronic polymers are types of plastics that conduct electricity. Scientists found that by using different concentrations of two solvents, they could control the movement of electrons within the polymers and increase or decrease the plastic's conductivity.
"Our analysis suggests that one day these polymers could conduct electricity even better than copper, which is currently the most widely used conductor," said Arthur Epstein, director of the Center for Materials Research and a professor of physics and chemistry at Ohio State.
The findings were presented March 19 in St. Louis at the annual meeting of the American Physical Society.
Polymers are made up of long chains of molecules, like
threads, that tend to be wavy and move in different directions. However, there are pockets of threads in the polymers that are straight. Epstein, working with Randolph Kohlman, a former doctoral student at Ohio State, found that the straight threads conduct electricity better than wavy threads.
"By controlling how straight the polymer chains are, we can control how easily electrons can move through the polymer chains, Epstein said. "We can make it become either a better conductor or a poorer conductor by mixing them with different chemical solvents that cause the wavy threads to become straight."
Working with chemistry professor Alan MacDiarmid of the University of Pennsylvania, Epstein found that when chloroform is used as a solvent for a polymer a lower level of conductivity results. When the plastics are mixed with the solvent m-Cresol, the electrical conductivity is increased by as much as 1,000 times.
While the polymer conducts electricity at just .1 percent that of copper, it is a better conductor than silicone, and can conduct almost as well as lead, Epstein said.
"Conductivity covers an enormous range," he said. "The polymer is highly conductive and more appropriate than copper for applications that do not require a high level of conductivity."
Low-conducting electronic polymers can be used as coatings for anti-static fibers in carpet or clothing. High-conducting plastics could be used to shield electromagnetic radiation emitted by devices such as cellular telephones or electronic brakes in cars.
"The same type of polymer that could be used as a shield can also be used as a conductor," Epstein said. "The difference is that the amount of conductivity you need for a conductor to remove static charge is much less than the amount of conductivity you need for shielding."
Another use for a high-conducting polymer could be as a replacement for tin-lead solder, which is used to make a connection between two metal contacts in computers. The metal solder makes recycling of the computer's plastic circuit boards costly. Using a polymer to make those contact connections could enable industry to recycle the plastic components more cheaply.
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Contact: Arthur Epstein, (614) 292-1133
Written by Kelli Whitlock, (614) 292-9475