"Impossible" 2D material is light as plastic and stronger than steel
Engineers at MIT have developed a new ultrathin material that’s as light as plastic but stronger than steel. The durable material could be used in vehicles or electronics, and makes use of a manufacturing technique that was previously thought impossible.
Polymers are versatile materials, of which plastics are perhaps the most well known examples. Under a microscope, polymers usually look like squiggly threads, one-dimensional chains of units called monomers, but they can be coaxed into three dimensional shapes through manufacturing methods like injection molding.
However, getting polymers to bind together to form two-dimensional sheets has been surprisingly difficult. While some teams have had some success, the resulting materials have faults that reduce their strength or other desirable properties.
But for the new study, the MIT scientists say they’ve developed a new production method that allows polymers to form 2D sheets while keeping their strength intact. The team started with melamine as the monomer, which has a structure of carbon and nitrogen rings. In a solution exposed to just the right conditions, these molecules grow sideways into disk shapes, which then stack on top of each other, with hydrogen bonds holding the layers together.
“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,” said Michael Strano, senior author of the study. “This mechanism happens spontaneously in solution, and after we synthesize the material, we can easily spin-coat thin films that are extraordinarily strong.”
The team calls the material 2DPA-1, and it has a few impressive properties. Although it’s extremely thin and lightweight, the polymer has a yield strength that’s twice that of steel, and it takes up to six times more force to deform it than bulletproof glass. It’s also completely impermeable to gases and liquids.
With these kinds of abilities, 2DPA-1 could make for a lightweight, durable, watertight coating for vehicles, electronic devices like smartphones and the like, or even used as a construction material.
“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,” said Strano. “It has very unusual properties and we’re very excited about that.”
The team says that the production method is easily scalable, and could be tweaked to make other types of materials.
The research was published in the journal Nature.