Credit: Hyun Suk Wang/Athina Anastasaki
A simple new method can break down commercial polymethacrylates, even if they contain additives or are dyed.
Acrylic polymers such as poly(methyl methacrylate)—the plastic used in Plexiglas—are durable materials with a huge variety of commercial applications. But the all-carbon backbones that give these plastics their strength also make them difficult to break down for chemically recycling.
“Every polymer, in principle, can be depolymerized if you heat it to the right temperature,” says polymer chemist Athina Anastasaki of ETH Zurich. But the reality is that a lot of plastics will burn or degrade before that temperature is reached.
She and her group previously found that polymethacrylates made via controlled radical polymerization can be unzipped with heat, but that process works only if the polymer has end groups that can trigger depolymerization, which commercial plastics typically do not.
Now, they have found a way to disassemble any polymethacrylate, regardless of end groups. The process doesn’t require any fancy reagents—just light, a little heat, and a chlorine radical source (Science 2025, DOI: 10.1126/science.adr1637)
“We can take a commercial polymer that does not have any weak points” and turn it back into its constituent monomers, says Anastasaki.
The discovery was somewhat serendipitous, she adds. Her graduate student Hyun Suk Wang was following up on work from Brent Sumerlin’s lab at the University of Florida, using a photocatalyst to break down poly(methyl methacrylate). He found that if he used 1,2-dichlorobenzene as the solvent, the depolymerization worked even without the photocatalyst.
The depolymerization does not depend on the polymer end groups.
So they set about figuring out what was going on.
The researchers found that dichlorobenzene produces a small quantity of chlorine radicals when it’s exposed to violet light. The radicals pluck hydrogen atoms from various points along the polymer backbone. At every point where a hydrogen atom is snatched, the polymer backbone breaks and a new carbon-centered radical forms, kicking off multiple simultaneous depolymerization reactions.
As long as they heated the polymer to above 90 °C and kept the light on, the researchers learned, they could depolymerize polymethacrylates featuring all kinds of end groups. The reaction even worked on commercial samples of colored Plexiglas.
The researchers also found they could recycle the same solvent for multiple depolymerizations after removing the monomer products. “You only sacrifice a small amount of chlorine” with each depolymerization, Anastasaki says, so the reaction is just as effective in solvent that has been recovered and reused.
“I think it’s a really excellent paper” with the potential to inspire a lot of future research, says Krzysztof Matyjaszewski of Carnegie Mellon University, an expert in radical polymer chemistry who was not involved in the work. The reaction is somewhat slow, but the yield is high, the conditions are simple, and it works on colored plastic, which are all commercially relevant qualities, he adds.
Anastasaki says that she and Wang have patented the process and that there are already two companies interested in the technology. Meanwhile, she and her group are continuing to explore ways to build on their discovery. For example, they’re investigating whether it’s possible to use a different radical source in more environmentally benign solvents and if there’s a way to initiate the radical reaction with just heat instead of light.
Chemical & Engineering News
ISSN 0009-2347
Copyright © 2025 American Chemical Society
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