Mechanical chemistry

[Dr Mordrid]

Article....

New way to manipulate matter is discovered

CHAMPAIGN, Ill., March 22 (UPI) -- The U.S. inventors of self-healing plastic have come up with yet another invention: a way to make chemicals react the way they want them to.

The University of Illinois researchers have discovered how to manipulate matter in such a way as to 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.

The researchers say their invention might lead to the development of materials that readily repair themselves, or clearly indicate when they have been damaged.

"This is a fundamentally new way of doing chemistry," said Professor Jeffrey Moore, corresponding author of the study. "By harnessing mechanical energy, we can go into molecules and pull on specific bonds to drive desired reactions.

"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."

The technique is described in the current issue of the journal Nature.

[NetSnake]

I read the full article yesterday.
Very interesting but they are really far away from this:

The researchers say their invention might lead to the development of materials that readily repair themselves, or clearly indicate when they have been damaged

a few details about the experiment

http://www.nature.com/news/2007/070319/full/070319-8.html

The clever experiment proves that mechanical forces can activate reactions in a controlled way, and so could open up a whole new avenue for synthetic chemists to explore.

Jeffrey Moore, at the University of Illinois at Urbana-Champaign, Urbana, and colleagues performed their trick with a specially designed polymer. Their polymer chain has inserted halfway along it a molecular fragment called a mechanophore, which includes a tiny ring of just four carbon atoms. Because carbon finds it hard to form bonds at such sharp angles, this ring is strained, and is inclined to burst open if given a nudge.

Moore's team provided the nudge with ultrasound — a blast of high-frequency sound that cannot be heard by the human ear. This does two things to a solution containing tangled strings of the special polymer. First, the sound waves create a flow in the solution that untangles each polymer string, beginning at one end. This provides a tugging force as one end of the polymer is pulled. Second, the ultrasound creates bubbles in solution many times bigger than the polymer molecules. As these bubbles burst, they both speed up the flow and the untangling of the polymers, and add a bang of mechanical energy.

Together, these forces rip apart the four-carbon ring. "We're pulling the atoms apart as opposed to just letting them do what they would like to do thermally," Moore says.



Pulled into place

There is another clever twist in this tangled tale, the researchers report in Nature1. In heat- or light-triggered reactions, the energy provided allows bonds to break, but there is no directional element to the reaction.

In this case, though, the tugging of the polymer strand means that the molecule is being stretched out. "We have a force that's applied in a specific direction," says Moore. This helps to determine the shape of the final, broken product.

The direction of pull means that the polymer is stretched and straightened out, making the same product regardless of its original shape.

The mechanophore can be inserted into the polymer in two different ways, making two different shapes out of the long, unbroken molecule (see diagram). But the pulling force straightens out the polymer in such a way that the snapped version always looks the same.

If heat had broken the bond, this wouldn't be true — there would be two differently-shaped snapped polymers. And these could react with other molecules in different ways, making different products. But with the mechanical break, only one final product can be made.