We are now modifying the molecular surface in such a way as to
enhance its effect on nearby molecules. This is quite unexpected but
will certainly impact industrial process sooner or later.
As posted before we have entered the age of engineering molecules
directly to improve effectiveness and clearly getting way more
confident and much less surprised. Again though it is early days
although it is clear that chemistry is well on the way to been what
electrical engineering became a few decades ago and biology became
more recently.
They all support each other and the results remain wondrous.
Molecular levers
may make materials better
by Staff Writers
Durham, NC (SPX) Dec 26, 2012
In a forced game of
molecular tug-of war, some strings of atoms can act like a lever,
accelerating reactions 1000 times faster than other molecules. The
discovery suggests that scientists could use these molecular levers
to drive chemical and mechanical reactivity among atoms and
ultimately engineer more efficient materials.
"We are
interested in designing new, stress-responsive materials, so we are
trying to develop reactions that are very slow normally but that can
be accelerated efficiently by force," said Duke chemist Steve
Craig, who headed the research.
In recent experiments,
Craig and his team found that a molecule made with a polynorbornene
backbone can act as a lever to open a ring embedded within the
molecule 1000 times faster than a similar ring being tugged at on a
polybutadiene scaffold. The results, which appear Dec. 23 in Nature
Chemistry, suggest that a simple change in the backbone may affect
the how fast mechanically assisted reactions occur.
Scientists are
interested in this type of molecular tug-of-war because many
materials break down after repeated cycles of tugging, stress and
other forces.
"If we can
channel usually destructive forces into constructive pathways, we
could trigger reactions that make the material stronger when and
where it is most useful," Craig said. Researchers might then be
able to extend the material's lifetime, which might in the long term
have applications ranging from composites for airplane frames to
biomedical implants.
In the experiment,
Craig, who is a professor and chair of the chemistry department, and
his team used the equivalent of microscopic tweezers to grab onto two
parts of atomic chains and pulled them so that they would break open,
or react, in certain spots.
The team predicted
that one molecule would react more efficiently than the other but was
surprised to find that the force-induced rates differed by three
orders of magnitude, an amount that suggests that the polynorbornene
backbone can actually accelerate forced reactions the way a crowbar
quickens pulling a nail from a wall.
Craig said changes to
the molecular group undergoing the reaction may have a much smaller
effect than changes to nearby, unreactive molecules like those on the
backbone.
It is also a good
starting point to identify other molecular backbones that are easy
to make and have the largest response to changes in nearby reactions,
features Craig said might help in developing even better, more
responsive materials.
The research was
supported by the U.S. Army Research Laboratory, the Army Research
Office and National Science Foundation. "A Backbone Lever Arm
Effect Enhances Polymer Mechanochemistry." (2012) Klukovich, H.
et al. Nature Chemistry. AOP. DOI: 10.1038/NCHEM.1540
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