A team of chemists at the University of Nebraska-Lincoln have created the world's first plastic magnets. It took 13 years of painstaking investigation, but Andrzej Rajca, a professor of chemistry, Suchada Rajca, his wife and research partner as a research assistant professor at Nebraska, and doctoral candidate Jirawat Wongsriratanakul finally achieved success earlier this year.
The results of that research, funded by the National Science Foundation with support from NU's Center for Materials Research and Analysis, were published in the Nov. 16 issue of Science, the weekly journal of the American Association for the Advancement of Science.
"There are already known organic magnets, but they are based on crystals of small molecules," Rajca said. "What is unique about this research is this is the first organic polymer that can be said to be magnetic."
A polymer is a large, often chainlike molecule that may consist of repeated linked units of relatively small molecules. An organic polymer is carbon-based and therefore an organic polymer that is essentially a plastic magnet, no metal required.
"This was predicted more than 30 years ago and a large volume of work has been done on this, especially in Japan and Europe," Rajca said. "We have worked on this since 1988 when I was an assistant professor at Kansas State. We essentially made larger and larger molecules with different arrangements of unpaired electrons in order to figure out how to make this polymer. It was a gradual approach, one step at a time."
Rajca, who moved his laboratory to NU's Hamilton Hall when he joined the Nebraska faculty in 1992, said no one should expect to stick a plastic magnet to a refrigerator door any time soon, however. That's because the magnetic polymers are unstable unless they are in an oxygen-free environment at temperatures below 10 degrees Kelvin (more than 440 degrees below zero Fahrenheit; absolute zero, the point at which all motion stops, is zero degrees Kelvin).
Nevertheless, he said he's relatively confident that the problems of stability and low temperatures can be overcome, if only because his team has already succeeded in proving one of the predictions made by Japanese theoretical chemist Noboru Mataga in 1968.
"Mataga predicted that it should be possible to do it (create organic magnetic polymers). He also predicted that it can be done at room temperature," Rajca said. "But theorists are always ahead of experimentalists and although it's possible to predict, it does not mean that we immediately know how to do it."
Rajca said he can only speculate about possible uses for the new polymers if (or when) the problems with stability and temperature are solved. To illustrate the point, he compared his team's discovery to the discovery of the first organic conducting polymers more than 20 years ago by a team that included Nebraska graduate and Nobel Prize winner Alan Heeger.
"At the time they were discovered, people thought they could be made into very light conducting wires that could replace metals as conductors of electricity," Rajca said. "But about 10 years ago, it was discovered that they can actually be used in a completely different way, as light-emitting diodes, and now several companies are actively working on that particular application. It turned out that these conducting polymers are not competitive as conductors.
"The real satisfaction for us at the moment is having made this discovery -- that it is possible to make an organic polymer that is magnetic. This is the nature of basic research. We try to go after something completely new, that was not thought possible."
Andrzej Rajca Group at University of Nebraska-Lincoln
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