New lightweight material is stronger than steel
The new substance is the result of a feat thought to be impossible: Polymerizing a material in two dimensions

Date:
February 2, 2022
Source:
Massachusetts Institute of Technology
Summary:
Chemical engineers have created a new material that is stronger
than steel, as light as plastic, and can be easily manufactured
in large quantities.



FULL STORY ========================================================================== Using a novel polymerization process, MIT chemical engineers have created
a new material that is stronger than steel and as light as plastic,
and can be easily manufactured in large quantities.


==========================================================================
The new material is a two-dimensional polymer that self-assembles
into sheets, unlike all other polymers, which form one-dimensional, spaghetti-like chains.

Until now, scientists had believed it was impossible to induce polymers
to form 2D sheets.

Such a material could be used as a lightweight, durable coating for
car parts or cell phones, or as a building material for bridges or other structures, says 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,"
he says. "It has very unusual properties and we're very excited about
that." The researchers have filed for two patents on the process they
used to generate the material, which they describe in a paper appearing
today in Nature. MIT postdoc Yuwen Zeng is the lead author of the study.

Two dimensions 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 three-dimensional objects,
such as water bottles, using injection molding.



========================================================================== Polymer scientists have long hypothesized that if polymers could be
induced to grow into a two-dimensional 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. One
reason for this was that if just one monomer rotates up or down, out
of the plane of the growing sheet, the material will begin expanding in
three dimensions and the sheet-like structure will be lost.

However, in the new study, Strano and his colleagues came up with a new polymerization process that allows them to generate a two-dimensional
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," Strano says. "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,"
Strano says.



========================================================================== Light but strong The researchers found that the new material's elastic
modulus -- 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," Strano says. "This kind of barrier coating could be used to protect metal in cars and other vehicles,
or steel structures." Strano and his students are now studying in more
detail how this particular polymer is able to form 2D sheets, and they
are experimenting with changing its molecular makeup to create other
types of novel materials.

The research was funded by the Center for Enhanced Nanofluidic Transport
(CENT) an Energy Frontier Research Center sponsored by the U.S. Department
of Energy Office of Science, and the Army Research Laboratory.

========================================================================== Story Source: Materials provided by
Massachusetts_Institute_of_Technology. Original written by Anne
Trafton. Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* Polymer_film ========================================================================== Journal Reference:
1. Zeng, Y., Gordiichuk, P., Ichihara, T. et al. Irreversible
synthesis of
an ultrastrong two-dimensional polymeric material. Nature, 2022
DOI: 10.1038/s41586-021-04296-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220202111732.htm

--- up 8 weeks, 4 days, 7 hours, 13 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)