MIT Scientists Create 2-Dimensional Polymers As Strong As Steel
Science does not respect timetables. Sometimes it takes years or even decades of experiments, blind alleys, and failures before a breakthrough occurs. Scientists at MIT have been trying for two decades to make a 2-dimensional polymer, something that all their theories and models suggested was possible but could never be actually created in the lab. Scientists had convinced themselves it was impossible to induce polymers to form 2D sheets.
According to an MIT blog post, MIT chemical engineers have created a new material using a novel polymerization process that is stronger than steel and as light as plastic. The best part is, it can be easily manufactured in large quantities. Prior to this breakthrough, all polymers formed one dimensional, spaghetti-like chains. The new material is a two dimensional polymer that self-assembles itself into sheets.
It 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, a professor of chemical engineering at MIT and senior author of the new research 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.”
Polymers & Monomers
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 techniques.
Polymer scientists have long hypothesized that if polymers could be induced to grow into a 2-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 2-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.
I may have been a failure at organic chemistry in college, but I know hydrogen bonds are some of the strongest in the world of chemistry. That’s one reason why it takes so much energy to break the hydrogen and oxygen atoms apart in a molecule of water.
“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 2DPA-1 has an elastic modulus — a measure of how much force it takes to deform a material — that is between 4 and 6 times greater than bulletproof glass. They also found that its yield strength — a measure of how much force it takes to break a material — is twice that of steel. Yet it has only about one-sixth the density of steel.
Matthew Tirrell, dean of the Pritzker School of Molecular Engineering at the University of Chicago, who was not involved in the research, 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 high strength to weight ratio is important, such as new composite or diffusion barrier materials.”
Impermeable To Gases & Liquids
Another key feature of 2DPA-1 is that it is impermeable to gases and liquids. While other polymers are made from coiled chains with gaps that allow gases and liquids to seep through, the new material is made from monomers that lock together like LEGOs, which means gas and liquid molecules cannot squeeze between them. “This could allow us to create ultra thin 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, an Energy Frontier Research Center sponsored by the U.S. Department of Energy Office of Science, and the Army Research Laboratory. There’s a lesson to be learned from that. This kind of research requires significant funding — more than private enterprise could ever justify. At a time when everything governments do is labeled by some as a waste of money and an affront to personal liberty, this might be the moment to give credit where credit is due, Tucker Carlson and his brigade of anti-democracy brigands notwithstanding.
The Takeaway
You never know where stuff created in laboratories may lead. The glue on sticky notes was the result of a failed experiment trying to make advanced adhesives that could bond the wings of airplanes to the fuselage. Might a super-tough impermeable coating make the transportation of hydrogen economically feasible? Could it end salt corrosion on highway bridges or reduce the weight of cars and trucks so they would use energy more efficiently?
If you like to dabble in the stock market, this is the kind of idea that could create significant wealth for patient investors who are able to take a long term approach. It’s actually quite exciting, when you think about. So many possibilities and thousand more no one has even thought of yet. Hold onto your hats. This could be bigger than Tang!
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