Pubblicato in: Istruzione e Ricerca

2DPA-1. Leggero come la plastica e più robusto dell’acciaio. – Nature.

Giuseppe Sandro Mela.

2202-06-11.

2022-02-08__ Nature 001

Nature. Irreversible synthesis of an ultrastrong two-dimensional polymeric material

Polymers that extend covalently in two dimensions have attracted recent attention1,2 as a means of combining the mechanical strength and in-plane energy conduction of conventional two-dimensional (2D) materials3,4 with the low densities, synthetic processability and organic composition of their one-dimensional counterparts. Efforts so far have proven successful in forms that do not allow full realization of these properties, such as polymerization at flat interfaces5,6 or fixation of monomers in immobilized lattices7,8,9. Another frequently employed synthetic approach is to introduce microscopic reversibility, at the cost of bond stability, to achieve 2D crystals after extensive error correction10,11. Here we demonstrate a homogenous 2D irreversible polycondensation that results in a covalently bonded 2D polymeric material that is chemically stable and highly processable. Further processing yields highly oriented, free-standing films that have a 2D elastic modulus and yield strength of 12.7 ± 3.8 gigapascals and 488 ± 57 megapascals, respectively. This synthetic route provides opportunities for 2D materials in applications ranging from composite structures to barrier coating materials.

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Questo articolo è bello da leggersi, ma alquanto tecnico. Ne riportiamo alcuni aspetti applicativi.

«The new 2D polymer, named 2DPA-1, is stronger than steel and as light as plastic»

« his mechanism happens spontaneously in solution, and after we synthesize the material, we can easily spin-coat thin films that are extraordinarily strong»

«force it takes to deform a material — is between four and six times greater than that of bulletproof glass»

«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»

«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»

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Sci News. Scientists Create Ultrastrong Polymeric Material

The new 2D polymer, named 2DPA-1, is stronger than steel and as light as plastic; it self-assembles into sheets, unlike all other polymers, which form spaghetti-like 1D chains.

Polymers, which include all plastics, consist of chains of building blocks called monomers. These chains grow by adding new molecules onto their ends.

Once formed, polymers can be shaped into 3D objects, such as water bottles, using injection molding.

Polymer scientists have long hypothesized that if polymers could be induced to grow into a 2D sheet, they should form extremely strong, lightweight materials.

However, many decades of work in this field led to the conclusion that it was impossible to create such sheets.

However, MIT Professor Michael Strano and and his colleagues came up with a new polymerization process that allows them to generate a 2D sheet called a polyaramide.

For the monomer building blocks, they use a compound called melamine, which contains a ring of carbon and nitrogen atoms.

Under the right conditions, these monomers can grow in two dimensions, forming disks.

These disks stack on top of each other, held together by hydrogen bonds between the layers, which make the structure very stable and strong.

“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,” Professor Strano said.

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

Because the material self-assembles in solution, it can be made in large quantities by simply increasing the quantity of the starting materials.

The researchers showed that they could coat surfaces with films of the material, which they call 2DPA-1.

“With this advance, we have planar molecules that are going to be much easier to fashion into a very strong, but extremely thin material,” Professor Strano said.

The scientists found that the elastic modulus of 2DPA-1 — a measure of how much force it takes to deform a material — is between four and six times greater than that of bulletproof glass.

They 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.

Another key feature of 2DPA-1 is that it is impermeable to gases. While other polymers are made from coiled chains with gaps that allow gases to seep through, the new material is made from monomers that lock together like LEGOs, and molecules cannot get between them.

“This could allow us to create ultrathin coatings that can completely prevent water or gases from getting through,” Professor Strano said.

“This kind of barrier coating could be used to protect metal in cars and other vehicles, or steel structures.”