New material has durability
combined with remoldability
a network of molecules, each holding
hands with four others. These molecules
are constantly switching who they hold
hands with, but the number of bonded
hands in the material always stays the
same. When heated, this molecular hand
swap speeds up. The molecular flexibility means that at high temperatures the
material can easily be remolded.
“You can do anything you want,”
Leibler says. “You can work it like wood,
you can make big parts if you want, and
the beauty of it is all of the ingredients are things that are already used in
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essentially fixed, the researchers report
in the Nov. 18 Science.
“They developed a unique and very
powerful approach that will have a
great deal of applications,” says polymer chemist Christopher Bowman of
the University of Colorado Boulder.
Superdurable plastics such as those
used for kitchenware and some car parts
are molded into shape and then “cured,”
turning them into one giant cross-linked
molecule. The molecules of softer plastics like those in soda bottles typically
aren’t held together with these strong
bonds and can be melted and reshaped.
To get an in-between material, scientists led by Ludwik Leibler of France’s
National Center for Scientific Research
in Paris mixed a regular epoxy resin with
acids and then added a zinc-based compound to help the other ingredients react.
The resulting material consists of
When heated, a sturdy
new plastic can be easily
remolded, repaired and
By Rachel Ehrenberg
A tough new plastic that’s easily healed
if damaged could find use in products
prone to getting beat up, such as paints
or parts for cars and sailboats. What’s
more, it can be recycled into completely
new products like plastic molding for
electronic devices or optical lenses.
Chemical bonds in the new material
continually break and re-form. At really
high temperatures, the bonding switcheroo makes the material malleable, but
the reactions are so sluggish at ordinary
temperatures that the material’s shape is
Tiniest car goes for a test-drive
Nanosized carbon vehicle lurches along with zap of electricity
By Rachel Ehrenberg
Scientists have created the tiniest electric car ever — although
it won’t be coming to your
local dealership anytime soon.
With four molecular wheels
and a carbon-based frame, the
nanoroadster is a step toward
devices that mimic the machinery of molecular life.
The researchers started with
little motorized “wheels,” molecules inspired by the motors
that some bacteria use to propel themselves, and attached them to a frame.
Carbon double bonds serve as axles
between two wheels; when the entire
unit is zapped with electricity, the double
bonds become single. This contorts the
axles, rotating the wheels and propelling the car forward, researchers report
in the Nov. 10 Nature. In test-drives on a
A miniature four-wheel vehicle (light gray) rolls
across a surface when zapped with electricity
that contorts the wheels’ axles.
copper surface, the car went as far as 20
nanometers — about 10 car lengths, says
organic chemist Ben Feringa of the University of Groningen in the Netherlands.
“The interactions with the surface
are very important,” Feringa says. “The
key is to not make it stick to the surface,
because it will never move, but also it
cannot fly away.”
Another difficulty of working at the
nanoscale is that when molecules are
close together they interact, and not necessarily in the way that you want, says
Paul Weiss, director of the California
NanoSystems Institute at UCLA.
“The biggest thing here is these four
motors operating together,” says Weiss.
“It’s really terrific work.”
Nature is adept at making such mini-
machines. Proteins transport cargo
inside cells and help muscles move, for
instance. Building similar molecules
that cooperate and carry out tasks could
lead to all sorts of machines and uses,
There are still kinks to iron out before
these little cars can be mass-produced
efficiently. The molecular machines are
made in a solution that’s then poured on
the copper surface, and only cars that
land right-side-up are drivable. But such
production issues should be relatively
easy to overcome, says Weiss.
“We’re really learning the forces
and the lay of the land at the nanoscale,”
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