A group of scientists from the University of Illinois at Urbana-Champaign (UIUC), USA, has found a new way to manipulate matter. Their method, which is described in the latest issue of the journal Nature and could open up many new possibilities in synthetic chemistry, uses mechanical forces----instead of light, heat, pressure or electrical potential----to control chemical reactions and thus obtain specific products that may otherwise not be attainable.
Jeffrey Moore and colleagues were able to use mechanical energy to go into the molecules and manipulate specific bonds within them, thus driving chemical reactions along a desired direction.
The technique was demonstrated using a specially designed polymer with an inserted molecular fragment called a mechanophore (which includes a ring of four carbon atoms). By applying force (ultrasound) to this system, the researchers were able to cause a well-directed rupture of the four-carbon ring and control which of several possible pathways the reaction chose to follow.
Figure: An overlay of three images at successive points during the force-induced chemical change. The strands represent polymer molecules attached to the mechanophore. The blue image is the start of the reaction. Elongation of the polymer caused by flow places tension on the mechanophore. The yellow image represents the end of the reaction. The green gradient in the background represents the velocity of the solvent molecules rushing past the polymer (the darker the color, the faster the solvent velocity). Credit: Dorothy Loudermilk and Ashley Levato, UIUC.
Potential applications of this new technique could include materials that more readily repair themselves or clearly indicate when they have been damaged. The mechanical energy stored in stressed polymers could be diverted into chemical pathways, such as self-healing reactions.
Other authors of the Nature paper are: Charles Hickenboth (lead author), Scott White, Nancy Sottos, Jerome Baudry, and Scott Wilson. The scientists are now looking forward to developing more mechanophores whose chemical reactivity can be activated using external forces.
