As
a research chemist at an IBM laboratory, Jeannette M. Garcia spends her
days mixing and heating chemicals in pursuit of stronger and more
easily recyclable plastics. Recently she followed a simple formula that
required mixing three components in a beaker. Somehow she missed a step,
leaving out a chemical. She returned to find her beaker filled with a
hard white plastic that had even frozen the stirrer.
Dr. Garcia tried grinding the mystery material, to no avail. Then she took a hammer to the beaker to free it.
That
laboratory error has led to the discovery of a new family of materials
that are unusually strong and light, exhibit “self-healing” properties
and can be easily reformed to make products recyclable.
The
materials — two new types of synthetic polymers — could have
transportation uses. Because of their recyclability, they also could
have an impact on consumer products, as well as on the industrial
packaging for microelectronics components.
The
findings were reported on Thursday in the journal Science by a research
team at IBM’s Almaden Research Laboratory in San Jose, Calif.
There
has been an explosion of new polymer materials in recent years, but
most of them are variants of existing synthetic classes that are
characterized by long chains of simpler molecules connected through
chemical bonds. The materials are today ubiquitous in modern life, found
in everything from paints and contact lenses to garments and batteries.
“They
are just pervasively used materials,” said James L. Hedrick, an
advanced organic materials scientist at IBM in San Jose. “This is the
polymer age.”
The IBM scientists say that this is the first distinctly new family that has been discovered in several decades.
They
said they had not yet named the new family, which they have code-named
“Titan” and “Hydro.” The materials are not yet ready for commercial use,
but the scientists said they had already begun working with several
universities on composite applications that could have a significant
impact on manufacturing and fabrication in the fields of transportation,
aerospace and microelectronics.
The
materials are known as thermosets because they are formed using a
heating process. Their strength comes from their three-dimensional
network of chemical bonds. The polymers have the rigidity of bones, one
of the strongest biological materials, and can be made as much as 50
percent stronger by blending them in composite form with materials like
carbon nanotubes. They also tend to perform better than other types of
polymers under high temperatures.
IBM
has invested heavily in new computational chemistry technologies that
rely on supercomputers. The researchers were able to build a computer
model of the new material, characterizing it in two distinct types, one
that was “soft and gooey” and the other extremely rigid.
“There
is this conventional wisdom out there that the main classes of polymer
materials have all been discovered,” said Bob Allen, a senior manager
for Chemistry and Advanced Materials Research at the laboratory. “But
with this approach that we’ve taken with heavy doses of computational
time, as well as hard-core laboratory synthesis, we’ve come up with a
new one.”
The
IBM finding evokes the discovery of Teflon, said Timothy E. Long, a
chemistry professor at Virginia Tech. “Serendipity is the mother of
invention.”
In
1938, while looking for alternative refrigerants, Roy Plunkett, a
DuPont chemist, inadvertently polymerized tetrafluorethylene,
accidentally creating one of the most slippery materials.
In
a perspective essay accompanying the research article in Science, Dr.
Long argued that the new materials represented a significant advance in
efforts to make consumer goods more easily recyclable, particularly
electronics, which have become a major waste problem.
“Thermosets
are designed to be exceptionally stable in terms of temperature and
mechanical properties; they are not designed to be reversible,” he said.
“To think about materials that have all of these properties, and which
are also recyclable, is an advance.”
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