Molecules That Play Traffic Cop

Tougher plastics for less money--that's one potential application of a new nanoscale technique for building polymers. It's a radically different way to change the physical properties of so-called monomers such as styrene, the raw material for polystyrene.

This inexpensive plastic is used to make toys and foam-plastic cups. Trouble is, it's not very sturdy. So when more durability is needed--say, for TV cabinets--the styrene is combined with other monomers.

Now, researchers at Northwestern University, led by materials scientist Samuel I. Stupp, have designed ultrathin molecules to act as traffic cops. They direct the styrene molecules to form ranks--to make internal structures that aren't natural. Stupp's "dendron rodcoil" molecules are very long and one-thousandth as thick as a human hair. Adding just 1% by weight to styrene causes a dramatic physical transformation--the formation of self-reinforcing internal structures.

Considerable work remains to be done before the traffic-cop molecules will be ready for commercial duty. But the Northwestern team believes that it has uncovered a new way to tailor plastics--and not just styrene. Stupp told the recent annual meeting of the American Chemical Society that the technique has already been used to modify other monomers.

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