jeudi 29 mai 2014

IBM discovers first new class of polymers in decades

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By May 15, 2014

A Scanning Electron Microscopy (SEM) image of the new ultra-strong polymer reinforced with...
A Scanning Electron Microscopy (SEM) image of the new ultra-strong polymer reinforced with carbon nanotubes (Image: IBM)
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The chemical tree got a bit of a shake this week with scientists at IBM announcing the discovery of the first new class of polymer materials in decades. Discovered using a combination of lab experiments and computer modelling, the new plastics have properties that could potentially have a huge impact in manufacturing, transportation, aerospace, and micro electronics.
Since the first synthetic plastics were invented in the 19th century, the use of polymers has spread from artificial billiard balls to become one of the key materials of the 21st century. They’re used so widely in modern life that this could almost be called a plastic age, though the names are rarely familiar with such non-household labels as polyesters, polyacrylates, polyethylene, polyolefins, polystyrene, epoxies, polyamides, and polyimides.
Despite this ubiquity, plastics aren't all that they should be. While they have a reputation for indestructibility, they’re actually very sensitive to the environment. Ultraviolet light, oxygen, heat, alcohols, and solvents can all destroy plastics in short order. Try using a polystyrene cup to measure out petrol and you’ll get a dramatic demonstration of this. They’re also very difficult to recycle because once they've been cured they can’t be remolded, and over time some can exude toxic chemicals if left in a landfill.
Up until now, polymer chemistry was regarded as a mature field where all the big discoveries have been made and it's now just a matter of filling in the details. It’s been decades since the last family of polymers was discovered, and most plastics research today involves combining, tweaking, and generally learning how to work plastics. It’s a bit like making advances in woodworking without discovering new species of trees. Now IBM have discovered the first new family of trees ... or rather, polymers in decades
We call chemistry a science, but in many ways it's an art that relies on the experience and intuition of the chemist. Computational chemistry combines the empirical work in the synthetic polymer chemistry lab with the modelling power of the computer to predict chemical reactions. It doesn't replace experiments, but it does cut out a lot of the trial and error. And it’s through computational chemistry that the new polymers were discovered.
The IBM polymers consist of two related classes of plastic materials. They’re formed by combining paraformaldehyde and 4,4ʹ-oxydianiline in what’s called a condensation reaction. When heated to 250⁰ C (482⁰ F) the material becomes very strong as covalent bonds form and the solvent is forced out, forming the first of two versions of the polymer. Both versions are highly elastic, resistant to solvents, and are recyclable. One version can even self-heal.
Infographic explaining the new polymer discovered by IBM (Image: IBM)
These polymers also show new physical properties. The first version is lightweight, stiff, resistant to cracking, shows more strength than bone, and can also turned into new polymer structures with half again as much strength. However, it is very brittle, like glass. When mixed with carbon nanofibers and heated, it forms an extremely strong, lightweight composite material that is similar to metal, yet has a degree of self-healing when cracked.
Another version of the plastic forms an elastic gel because it’s formed at low temperature and traps the solvent in its molecular network. This gel is not only very stretchy, but It’s “self-healing” because if you cut a bit in two, they bond back together again in seconds when they touch. According to IBM, this property makes the gel polymer useful as an adhesive, a way of making other polymers self-healing, or as a method for transporting dyes or medicines.
Both versions are also recyclable. Water doesn't affect the polymer, but when the water is acidic, the polymer melts and can be recovered and reformed into new products. This property means that the plastic can be selectively removed without affecting surrounding materials, which has great potential for the semiconductor industry, manufacturing, and advanced composites.
“Although there has been significant work in high-performance materials, today’s engineered polymers still lack several fundamental attributes," says James Hedrick, Advanced Organic Materials Scientist, IBM Research. "New materials innovation is critical to addressing major global challenges, developing new products and emerging disruptive technologies. We’re now able to predict how molecules will respond to chemical reactions and build new polymer structures with significant guidance from computation that facilitates accelerated materials discovery. This is unique to IBM and allows us to address the complex needs of advanced materials for applications in transportation, microelectronic or advanced manufacturing.”
The IBM team’s research was published in Science.
The video below shows the new polymer in a lab setting.
Source: IBM

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