“Pluripotent” plastic: from one starting polymer, many materials

A material developed by Prof. Stuart Rowan can turn into plastics that range from stretchy and bendy to stiff and rigid. This versatility may be useful for engineers working in resource-scarce environments like outer space.

Drifting at sea, isolated on a space station, or stuck in a war zone, engineers trying to build new things or patch together a repair are often constrained by the materials they have at hand. But what if they had one single polymer that they could coax into anything from a rubber band-like material or a ball of silly putty to a flexible sheet of plastic or a stiff, molded device?

Researchers at the University of Chicago Pritzker School of Molecular Engineering (PME) have now developed such a material, which they call a “pluripotent plastic.” Like pluripotent stem cells which can give rise to any type of adult cell in the human body, their plastic, described in the journal Science, can take on many final forms.

“We believe, this is the first example of a synthetic material that exhibits pluripotent behavior,” said Stuart Rowan, the Barry L. MacLean Professor for Molecular Engineering Innovation and Enterprise at PME and senior author of the new work. “We believe that it paves the way toward a different way of thinking about material design.”

To develop the new material, Rowan worked with PME assistant professor Shrayesh Patel, graduate student Nicholas Boynton, and colleagues at Argonne National Laboratory, the U.S. Army Research Laboratory, NASA, and the National Institute for Standards and Technology (NIST).

The pluripotent material is made up of polymers containing “dynamic covalent bonds,” which can break and re-form reversibly. Heating the material only to low temperatures (around 60 °C) allows the formation of more bonds, resulting in stiff/high strength materials at room temperature. These could be used to plastic utensils, among other things. Heating to higher temperatures (around 110 °C) results in fewer bonds being formed and, in turn, a more soft, extensible material that can be used for instance, as a pressure-sensitive adhesive.

“We were surprised by how many different mechanical properties we could get,” said Boynton. “From this single feedstock material, we can turn it into something that behaves like a hard, high-strength material or something that’s quite flexible, like a rubber band.”

Importantly, the process is reversible. By adjusting the temperature between the two extremes, the researchers showed that they could fine-tune the properties of the materials, giving them a variety of properties and functions.

Moreover, the resulting material—although stable at room temperature—could be tempered again at a different temperature to access a new and different state.

“If you’re going to live on the moon or Mars, you can’t take a bunch of materials with you, and you don’t have Amazon Prime shipping, so it’d be great if you have this one material that you can turn into a bunch of different stuff,” said Boynton.

In addition to being employed as on-demand reuse materials in resource-scare environments, such as on the Moon or Mars, this work also opens the door to different approaches to plastic recycling (where there is no need to separate out the different plastics we use today).

The team is now investigating how to improve the range of mechanical properties that can be imbued in their pluripotent materials with the goal of creating materials to replace current plastics as well as materials with new functional properties.

“We want to reframe the way we think about designing materials,” said Rowan. “Instead of designing one material for one application, let’s flip that on its head and see if we can make one material that can be differentiated to be useful for many applications.”

Citation: “Toward pluripotent materials through tempering of dynamic covalent polymer networks,” Boynton et al, Science, February 1, 2024. DOI: 10.1126/science.adi5009

Funding: National Science Foundation, National Science Foundation Materials Research Science and Engineering Center (MRSEC), a NASA Space Technology Graduate Research Opportunity, Army Research Laboratory, NIST Center for Hierarchical Materials Design