“Designer” plastic can be recycled and reused

An new class of polymers that matches popular plastics’ thermal and mechanical properties, but has the potential to be recycled and reused indefinitely, has been developed by scientists in the U.S., China and Saudi Arabia. The work has been reported recently in various scientific journals including Science, Chemistry World and Ecotextile News. 

However, designing chemically recyclable plastics with desirable properties remains challenging. Eugene Chen of Colorado State University, who led the study together with Laura Falivene from the King Abdullah University of Science and Technology in Saudi Arabia, explains the issues. “First, polymers that can be easily deconstructed typically don’t exhibit good properties. Second, highly crystalline materials tend to be brittle and easy to break, and third, to achieve high crystallinity for better mechanical properties, one must be able to precisely control the stereochemistry of the polymerization,” Chen says. 

The team has now prepared a new class of polythioesters that defies these trade-offs. “In addition to being fully recyclable, our polymers exhibit high mechanical strength, toughness, ductility and thermal stability,” says Chen. The material could offer a sustainable alternative to traditional plastics, he says although integrating these polymers into current recycling streams is a problem. However, “once separated from the mixed waste stream, the new plastic can be selectively and cleanly deconstructed into its building blocks,” he says.