Pimp My Polymer

How antioxidants are changing plastic manufacturing for the better—and the greener. By Kiera Butler

Antioxidants aren’t just good for us—they’re good for plastics, too. Researchers at Carnegie Mellon University have figured out how to use common antioxidants like vitamin C to make a popular kind of plastic manufacturing more efficient—and much greener.

When Carnegie Mellon scientists developed atom transfer radical polymerization (ATRP) in 1995, it was considered a breakthrough in plastic technology. In traditional processes, once a polymer chain reaction is started, it goes quickly and is difficult to control. ATRP makes it possible to grow polymer chains one molecule at a time, which allows plastic manufacturers to control the properties of the plastics they create.

According to Dr. James Spanswick, associate director of the Center for Macromolecular Engineering at Carnegie Mellon University, more than a hundred companies, including L’Oreal, Bayer, and Eastman-Kodak, are using or plan to use ATRP to make products.

But the old process created byproducts—and getting rid of those byproducts required large quantities of catalyst, usually a metal such as copper, which in turn had to be disposed of. “The copper turned things green—then you would have to get rid of it,” said Spanswick. “It’s a nuisance. You had to pass it through columns, or extract it out with water. It took a lot of time and water.” The amount of water required, combined with the fact that catalysts like copper don’t break down easily, made the process less than environmentally friendly.

In the new process, which is described in the current issue of the Proceedings of the National Academy of Sciences, a “benign reducing agent”—an antioxidant such as vitamin C or glucose—is added to the reaction to reduce the levels of copper as the polymer chain is built. This means that the reactions will now require roughly 1,000 times less catalyst.

“This new process is going to be much greener because there’s less catalyst involved and less requirement for purification,” said Robert Grubbs, a professor of chemistry at the California Institute of Technology, who won a Nobel Prize in chemistry last year for his work with polymers. “This will be a major change in the commercial application of this process.”

Most likely, the new process will appeal to more manufacturers, since in addition to being greener, it’s also cheaper: cutting down on catalyst means cutting down on the considerable cost of removing it.

Spanswick said it made sense that antioxidants were the key to solving ATRP’s biggest problem. “Antioxidants are good for you because they get rid of free radicals in your body—it’s a lot like what’s going on in the new ATRP process.”

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Professor Robert Grubbs of the California Institute of Technology won his Nobel Prize (2005 award) not for his work with Polymers but for the development of the metathesis method in organic synthesis

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