Originally Published MDDI October 2004

R&D DIGEST

Plastic Magnets Show Some Mettle

Heather Thompson

A team of scientists from the University of Durham in the United Kingdom has created the first magnet, formed from a polymer structure, that works at room temperature. The group, composed of researchers from the organic electroactive materials (OEM) research group and the department of physics at the university, used the magnet to pick up iron filings in their laboratory.

This is not the first plastic magnet to be developed. Previous models of magnets formed from polymer materials functioned only in extremely low temperatures. The first polymer magnet worked only at –10ÞK.

The new magnet does not yet operate at 100% efficiency, and its magnetic strength varies throughout the material. But, the researchers believe they will be able to better synthesize the magnetic properties and increase the magnet's overall efficiency. And, because it is functional at room temperatures, myriad uses for the polymer magnet may begin to take shape.

To create the magnet, the team manufactured two organic polymer compounds, one called emeraldine-base polyaniline (PANi) and the other named tetracyanoquinodimethane (TCNQ). PANi acts much like an electrical conductor and has metal-like properties. TCNQ was chosen becasue it can form charged-air particles, also known as free radicals, in a stable environment. By combining the two compounds (the team calls their creation PANiCNQ), teh team was able to contrive an ion-rich stable setting that is conductive in room temperatures.

Traditional magnets operate through the alignment of spinning electrons. For metallic-based magnets this function is relatively easy to create, but the plastic ones may take a little while to get going. When first formed, the plastics showed little signs of magnetism and continued to give weak results over the next months.

After three months in a sealed container, however, the original polymer developed magnetic properties. Because the structure is organic, it exhibits rising kinetic reactions with time. The team confirmed the development by examining x-ray diffraction that showed increasing alignment of the polymer chains.

Practical applications could be five or more years away, says the team's head researcher, Naveed Zaidi. He says, “The magnets have not yet reached the strength to compare with conventional metal magnets.” But the team is confident that they will be able to match the strength of regular magnets and are already considering a variety of applications. Zaidi says, “Our initial ideas for application is in magnetic or magneto-opto storage,” such as that used in computer hard disks. Medical applications might also be an option. Transducers in cochlear implants or magnets used in dental work, for example, may benefit from using the polymer magnet. “Replacing metal magnets with polymer magnets results in a lighter-weight implant,” says Zaidi. The plastics are also more conformable, meaning the magnetic properties could be customized depending on design needs, he adds.

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