March 21, 2007

Mechanical force used to control chemistry

This provides more clear evidence that the concept of site specific chemistry using mechanical placement of molecules is viable. This concept is the basis of molecular nanotechnology. This may become part of a bootstrapping pathway. This shows that those who said that we would not be able to mechnically control chemical reactions were wrong.

Researchers at the University of Illinois at Urbana-Champaign have found a novel way to manipulate matter and drive chemical reactions along a desired direction. The new technique utilizes mechanical force to alter the course of chemical reactions and yield products not obtainable through conventional conditions.

"This is a fundamentally new way of doing chemistry," said Jeffrey Moore, a William H. and Janet Lycan Professor of Chemistry at Illinois and corresponding author of a paper that describes the technique in the March 22 issue of the journal Nature.

"By harnessing mechanical energy, we can go into molecules and pull on specific bonds to drive desired reactions," said Moore, who also is a researcher at the Frederick Seitz Materials Laboratory on campus and at the university's Beckman Institute for Advanced Science and Technology. The directionally specific nature of mechanical force makes this approach to reaction control fundamentally different from the usual chemical and physical constraints. To demonstrate the technique, Moore and colleagues placed a mechanically active molecule – called a mechanophore – at the center of a long polymer chain. The polymer chain was then stretched in opposite directions by a flow field created by the collapse of cavitating bubbles produced by ultrasound, subjecting the mechanophore to a mechanical tug of war.

"We created a situation where a chemical reaction could go down one of two pathways," Moore said. "By applying force to the mechanophore, we could bias which of those pathways the reaction chose to follow."

Richard Smalley had said, "I agree you will get a reaction when a robot arm pushes the molecules together, but most of the time it won't be the reaction you want." This shows that mechanical force can be used to get the reaction you want.

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