Chemical engineers from MIT have created a new material using a new polymerization process, and it’s as light as plastic and stronger than steel. Moreover, it can also be easily manufactured in big quantities.
This new material is a two-dimensional polymer that self-assembles into sheets, which is unlike other polymers, that normally form one-dimensional, spaghetti-like chains. Until this new type of polymer was created, scientists thought that it was impossible to induce polymers to create 2D sheets.
According to the Carbon P. Dubbs Professor of Chemical Engineering at MIT, Michael Strano, the possibilities for the use of this material is great. Some ideas include making a durable, lightweight coating for cellphones or car parts, or possibly building material for bridges and other such structures. He is also the senior author of this new study.
Strano explains, “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.”
In the meantime, the research group has already filed for two different patents on the process they used to make the new material.
It Takes Two Dimensions
All plastics fall under the term “polymers,” which come of chains of building blocks known as monomers. When you add new molecules onto their ends, the chains grow. Once they’re formed, these polymers can be shaped into three-dimensional objects like water bottles by using injection molding.
Scientists that specialize in polymer have long since believed that if they could be ‘induced to grow into a two-dimensional sheet,’ that they would make incredibly strong yet lightweight materials. But years of work in this field led them to conclude that making these sheets was basically impossible. One particular reason for this was that ‘if just one monomer rotates up or down, out of the plan of the growing sheet, the material will begin expanding in three dimensions and the sheet-like structure will be lost.’
But in this new study Prof Strano and his team managed to come up with a brand new polymerization process which allows them to generate a two-dimensional sheet, which is called a polyaramide. As for the monomer building blocks, the scientists use a compound called melamine. This contains a ring of carbon and nitrogen atoms. When these are placed under the right conditions, the monomers can grow into two dimensions which form disks. When these disks stack up on top of each other, they are held together by hydrogen bonds between the layers, which is what makes the structure strong and stable.
Strano goes on to explain, “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.”
Since the material self-assembles in solution, it can also be produced in big quantities by just increasing the quantity of the starting materials. The research group also showed that they could coat surfaces with films of this new material, which is called 2DPA-1.
Strano also said, “With this advance, we have planar molecules that are going to be much easier to fashion into a very strong, but extremely thin material.”
Material That is Light But Strong
What the researchers have discovered about the new material’s elastic modulus, which is its measure of ‘how much force it takes to deform a material,’ is that it is between four and six time greater than bulletproof glass. Scientists also found that 2DPA-1’s yield strength, which is how much force it takes to break the material, is also twice that of steel, despite the fact that the material is only around one-sixth the density of steel.
In addition, another vital feature of 2DPA-1 is it’s impermeable to gases. Normally, other polymers are created from coiled chains with gaps, which allow gases to seep through. This new material, however, is made from monomers that lock together just like LEGOs do, which is why molecules can’t get in between them.
Strano goes on to say, “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.”
Alongside his students, Strano is examining the 2DPA-1 closely to see how this particular type of polymer is able to form 2D sheets, while experimenting with changing its molecular makeup to produce other types of new material.
You can find the research study published in the journal, Nature.
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