Wednesday, May 18, 2022

The material is stronger than steel but as lightweight as plastic

Polymerizing a material in two dimensions.

MIT chemical engineers have created a new material, i.e., a two-dimensional polymer stronger than steel and as light as plastic. The material can self-assemble itself into sheets and easily be manufactured in large quantities.

Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the senior author of the new study, said, “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. It has very unusual properties, and we’re very excited about that.”

Decades of work in this field suggest that it is impossible to create a lightweight and strong 2D sheets. One reason is if just one monomer rotates up or down, out of the plane of the growing sheet, the material will begin expanding in 3D, and the sheet-like structure will be lost.

Scientists in this new study have demonstrated a new polymerization process to create a 2D sheet called polyaramide. They used a compound called melamine for the monomer building blocks. The melamine compound contains a ring of carbon and nitrogen atoms.

The compound grows and forms disks under the right conditions. These disks stack on top of each other, held together by hydrogen bonds between the layers. The bond makes the structure very stable and robust.

Strano said, “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. This mechanism happens spontaneously in solution, and after we synthesize the material, we can easily spin-coat thin films that are extraordinarily strong.”

The newly created materials have elastic modulus, four and six times greater than that of bulletproof glass. As mentioned above, it is stronger than steel. Meanwhile, the force it takes to break the material is twice that of steel.

Matthew Tirrell, dean of the Pritzker School of Molecular Engineering at the University of Chicago, says“The new technique embodies some very creative chemistry to make these bonded 2D polymers.”

“An important aspect of these new polymers is that they are readily processable in solution, which will facilitate numerous new applications where a high strength to weight ratio is important, such as new composite or diffusion barrier materials.”

Strano said, “This could allow us to create ultrathin coatings that can completely prevent water or gases from getting through. This kind of barrier coating could be used to protect metal in cars and other vehicles, or steel structures.”

Journal Reference:

  1. Zeng, Y., Gordiichuk, P., Ichihara, T. et al. Irreversible synthesis of an ultrastrong two-dimensional polymeric material. Nature 602, 91–95 (2022). DOI: 10.1038/s41586-021-04296-3

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