Researchers at MIT and Boston University make ultra-thin plastic completely impermeable
Researchers at the Massachusetts Institute of Technology (MIT) have developed a super-thin plastic film to protect bridges and food. Rust, which corrodes iron components, and oxidation, which makes meat and other foodstuffs inedible, no longer stand a chance. The nanometre-thick film is as impermeable as graphene, but can be easily applied to the objects that need to be protected.
Still full after a long time
The experts inflated tiny balloons made of this material with nitrogen and were surprised to find that they were still full even after a long time – unlike balloons filled with hydrogen, for example. Although they rise high, they fall from the sky by the next day at the latest because the gas that carries them diffuses through the rubber shell.
Larger molecules such as nitrogen and oxygen, on the other hand, cannot pass through the new film. ‘Our polymer is quite unusual. It behaves like graphene, which is impermeable to gas due to its perfect crystal structure. But in this case, the impermeability is based on a different physical phenomenon,’ says MIT researcher Michael Strano.
He and Scott Bunch from neighbouring Boston University (https://www.bu.edu/) and MIT postdoctoral researcher Cody Ritt created a quasi-two-dimensional, i.e. unimaginably thin polymer that is held together by hydrogen bonds. They achieved this with the molecule melamine, which contains a ring of carbon and nitrogen atoms. This resulted in nanometre-sized discs that stacked on top of each other and closed virtually all pores.
Perfect protection for everything outdoors
In addition, the new structure has proven to be very stable, which makes it wear-resistant in its function as a protective layer. The film, called ‘2DPA-1’, is stronger than steel in terms of volume, but six times lighter. Conventional polymers allow gases to pass through because they consist of a tangle of spaghetti-like molecules that are loosely connected to each other. There are gaps between them that are permeable to most gases.
However, the new 2D polymer is essentially impermeable due to the way the layers of the discs adhere to each other. ‘With an impermeable coating like this, you could protect infrastructure such as bridges, buildings and basically anything that is exposed to the elements outdoors from destruction,’ Strano concludes.
