Science dean on lightweight polymer sheets stronger than steel: ‘Very creative chemistry’

Researchers from the Massachusetts Institute of Technology (MIT) have developed a lightweight material that they say is stronger than steel.

They used a breakthrough polymerization process to create a two-dimensional polymer that they say can be mass-produced, a feat that scientists previously did not believe was possible.

Their paper, published in the journal Nature, says the material self-assembles into sheets as opposed to materializing into one-dimensional chains like other polymers. The research team was led by Carbon P. Dubbs Professor of Chemical Engineering at MIT Michael Strano, with MIT post-doctoral research fellow Yuwen Zeng as lead author.

 The new technique “embodies some very creative chemistry to make these bonded 2D polymers,” said Matthew Tirrell, dean of the Pritzker School of Molecular Engineering at the University of Chicago. “These new polymers 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.”  

The new polymer could be used as a coating for car parts or cell phones, or as a building material in bridges or other structures, Stranos said. “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.” 

Also, it's impermeable to gases, making it useful for creating ultrathin coatings that can prevent water or gases from getting through, Strano said. 

Polymers are chains of building blocks called monomers. Polymers grow by adding new molecules onto their ends. They can be shaped into three-dimensional objects, such as water bottles. For years, polymer scientists believed that inducing polymers to form a two-dimensional sheet would lead to extremely strong, lightweight materials, but decades of research led scientists to believe that such an accomplishment was unattainable.

The MIT scientists said they discovered a process that allows them to generate a two-dimensional sheet called a polyaramide using a compound called melamine. In the right setting, monomers can grow in two dimensions, shaping disks that assemble on top of each other, by hydrogen bonds between the layers, which make the structure extremely robust. In order to break the material, it would take twice the force needed to break steel, although the material has approximately one-sixth the density of steel.

Two patents have already been filed by the researchers on the process for developing the material, which was backed by several government entities, including the U.S. Department of Energy Office of Science.