With some creative chemistry ideas, researchers at Massachusetts Institute of Technology (MIT) have made a lightweight material that’s stronger than steel and bulletproof glass.

The new material – a thin film known as 2DPA-1 – is a two-dimensional polymer that self-assembles into sheets, or stacks.

Instead of a conventional plastic made with scattered, spaghetti-like molecules, 2DPA-1 forms an airtight pillar of 2D sheets – a promising potential feature for car-part coatings or even building materials, according to Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the senior author of the new study.

“We don’t usually think of plastics as being something that you could use to support a building, but with this material, you can enable new things,” said Prof. Strano in a recent news release . “It has very unusual properties and we’re very excited about that.”

The unusual, self-assembling properties begin with a compound called melamine. Given the right conditions and the right chemical solvents, melamine, which contains a ring of carbon and nitrogen atoms, grows in two dimensions and forms disks.

Held together by hydrogen bonds, the parts form a strong, stable column – with no gaps between the monomers. With a tighter seal between the molecules, 2DPA-1 is impermeable to gases – a valuable feature, according to MIT graduate student Michelle Quien.

“We’ve found 2DPA-1 to be extremely impermeable to oxygen and believe 2DPA-1 coatings can be used as a barrier to oxygen, such as in preserving food,” Quien said in a Q&A with Tech Briefs below.

This chemical arrangement is an improvement compared to traditional plastic chemistries.

“Instead of making a spaghetti-like molecule, we can make a sheet-like molecular plane, where we get molecules to hook themselves together in two dimensions,” said Strano. “This mechanism happens spontaneously in solution, and after we synthesize the material, we can easily spin-coat thin films that are extraordinarily strong.”

How “extra”-strong exactly?

The researchers found that the new material’s elastic modulus — a measure of how much force is required to deform a material — is between four and six times greater than that of bulletproof glass. The team also found that its yield strength, or how much force it takes to break the material, is twice that of steel, even though the material has only about one-sixth the density of steel.

And with spin-coating and self-assembly, the material can be made in large quantities.

The MIT team has filed for two patents on the process they used to generate the material, which they describe in a recent paper appearing in Nature.

Strano and his researchers, including Quien and lead author and MIT postdoc Yuwen Zeng, are now studying in more detail how this particular polymer is able to form 2D sheets.

In a short Q&A with Tech Briefs below, Quien reveals more about which applications are a super-strong possibility.

Tech Briefs: What inspired this work?

Michelle Quien: Our lab has long been interested in 2D materials such as graphene. However, we recognize the difficulties in trying to create and modify these materials on a manufacturing scale.

So, we sought a way to make 2D materials with mild chemistry techniques. We were inspired by ultra-strong polymers such as Kevlar, and are happy to see 2DPA-1 combines the manufacturability of polymers with the ultra-low permeability and high strength of 2D materials like graphene.

Tech Briefs: How do you control the size and shape of the sheet?

Michelle Quien: We’re able to take a solution of 2DPA-1 and create films directly onto surfaces like silicon wafers. The method is called spin-coating, which results in extremely uniform films. Once we have a spin-coated film, we then can simply cut it into the shape and size we want.

Tech Briefs: How do you coat surfaces with this material?

Michelle Quien: Depending on the surface, we might be able to spin-coat 2DPA-1 directly on it. Otherwise, we have a method in which we can transfer a spin-coated 2DPA-1 film onto a different surface by suspending the film onto water.

Tech Briefs: Do you build layers of the 2D material on top each other to form a 3D material?

Michelle Quien: In the same sense that graphene is 2D and layered graphene, or graphite, is 3D, 2DPA-1 sheets that are stacked on top of each other form a 3D material. The 2DPA-1 films we create are actually multiple sheets stacked on each other; we’ve gotten these films as thin as 10 layers.

Tech Briefs: Could you explain in a little more detail how it could be used in a typical application?

Michelle Quien: Due to its ultra-strength, we believe that 2DPA-1 could be used in structural reinforcements, such as graphene-reinforced concrete. We’ve found 2DPA-1 to be extremely impermeable to oxygen and believe 2DPA-1 coatings can be used as barriers to oxygen, such as in preserving food.

We’re still exploring its permeability to other gases, but we could see 2DPA-1 films being used in gas separation processes such as carbon capture, helium separation, or hydrogen separation.

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