MIT says 2D polyaramids polymer film shows nitrogen permeability of 3.1 × 10⁻⁹ Barrer, far below existing polymer materials
2DPA-1 forms strong, layered sheets that block gases like helium, argon, oxygen, and methane
Tests using gas-filled micro-bubbles showed the film remains stable without leaking or collapsing
Its thin coatings could protect solar cells, infrastructure, vehicles, food packaging, and medicines from corrosion and degradation, claims the research team
Researchers at the Massachusetts Institute of Technology (MIT) have developed a lightweight polymer film made from 2D polyaramids (2DPA) that they claim is almost impenetrable to gas molecules. With nitrogen permeability measured at 3.1 × 10⁻⁹ Barrer, the film could be used as a protective layer to prevent corrosion in solar cells as well as to extend the shelf life of packaged food and medicines.
The team initially developed a 2-dimensional polymer in 2022 using a building block called melamine that contains a ring of carbon and nitrogen atoms. It exhibited the ability to self-assemble into molecular sheets using hydrogen bonds. Called 2DPA-1, this polymer is stronger than steel, according to the researchers, but has only 1/6th the density.
To test its gas permeability and material strength, the team created bubbles from the films, filling them with gas. Unlike most traditional polymers that are made up of spaghetti-like molecules, where gas trapped inside will seep out, deflating the bubble, the 2DPA-1 bubbles did not collapse.
“We set up a series of careful experiments to first prove that the material is molecularly impermeable to nitrogen,” explained Carbon P. Dubbs Professor of Chemical Engineering at MIT, Michael Strano. “It could be considered tedious work. We had to make micro-bubbles of the polymer and fill them with a pure gas like nitrogen, and then wait. We had to repeatedly check over an exceedingly long period of time that they weren’t collapsed, in order to report the record impermeability value.”
According to the team’s research, the new 2D polymer is essentially impermeable to not just nitrogen, but also other gases like helium, argon, oxygen, methane, and sulfur hexafluoride – at least 1/10,000th of any other existing polymer because of the way that the layers of disks stick to each other.
“That makes it nearly as impermeable as graphene, which is completely impermeable to gases because of its defect-free crystalline structure,” says the team. The 2DPA-1 can be an alternative to graphene coating films, which are difficult to scale up because graphene can’t be painted onto surfaces.
MIT researchers claim that thanks to the strong hydrogen bonds between the layered disks of 2DPA-1, a layer just 60 nm thick could extend the lifetime of a perovskite crystal to about 3 weeks. A thicker coating will further extend this protection, but its use can go far beyond solar cells alone.
“Using an impermeable coating such as this one, you could protect infrastructure such as bridges, buildings, rail lines — basically anything outside exposed to the elements. Automotive vehicles, aircraft and ocean vessels could also benefit. Anything that needs to be sheltered from corrosion. The shelf life of food and medications can also be extended using such materials,” Strano says.
The MIT research, titled A molecularly impermeable polymer from two-dimensional polyaramids, is now published in the Nature journal.