Building and breaking plastics with light: Chemists rethink plastic recycling

What if recycling plastics were as simple as flicking a switch? At TU/e, Assistant Professor Fabian Eisenreich is making that vision a reality by using LED light to both create and break down a new class of high-performance plastics. This innovative material enables truly circular recycling, as this process can be repeated over and over again, without any loss in quality.

This research, published in the Rising Stars edition of Advanced Materials, marks a breakthrough in sustainable chemistry and could reshape how we treat plastic waste in the future.

“In fact, we are molecular designers,” is how Eisenreich describes himself and his fellow scientists from the Polymer Performance Materials research group. In their labs at the Department of Chemical Engineering and Chemistry, that is what the focus is on.

“Our line of research centers on ‘design for recycling.’ We create new polymers to enable innovative recycling strategies for plastics. At the same time, we use organic (bio-based) materials, avoid toxic substances, and minimize waste to keep the entire process as sustainable as possible.”

Quality of polymer chains deteriorates

These polymers are developed to enable chemical closed-loop recycling, the ultimate goal of the research group. “Plastics typically consist of moldable polymer chains. Due to the current way in which plastics are usually recycled—in a nutshell: heating, melting, and reshaping—the quality of those polymer chains deteriorates over time. So you can’t keep doing that indefinitely, which means that new plastic will eventually have to be made anyway.”

Chemical closed-loop recycling is therefore the ideal alternative, according to Eisenreich. “With the right chemical reaction, a polymer chain can be selectively broken down into its original building blocks. These can then be reused to make exactly the same polymer again, with identical properties and quality.” Achieving this requires polymers designed to undergo that precise reaction—hence the focus of the Polymer Performance Materials group’s research.

Selectively splitting a polymer with light

Within that context, Eisenreich specifies his own research on photochemical recycling, powered by LED light. “Making polymers by means of light is relatively simple. But breaking and making them again in the same way, aka recycling, is much more complicated and therefore a whole new line of research. The challenge lies in using light to selectively split stable chemical bonds within the polymer, so the original building blocks can be recovered.”

Recently, Eisenreich and Ahsen Sare Yalin, a third-year Ph.D. candidate in his group, became the first to successfully pull off this trick in his lab.

Reshape the way we deal with plastic waste

“We see it as a breakthrough in sustainable chemistry that can reshape the way we deal with plastic waste in the future,” says Eisenreich. “At the moment, our designer polymer is still a niche material and therefore not suitable for everyday plastic applications. Instead, it is aimed at specialized uses, for example, as a recyclable adhesive that binds strongly to glass and other plastics.”

Ultimately, further development should broaden the application possibilities. Moreover, Eisenreich sees plenty of potential in closed-loop recycling technology with light. “I also work on 3D printing recyclable polymers using light, which is a very interesting process. You start with a liquid material that takes on a solid form as soon as light falls on it. You can use this process to print complex 3D objects.”

His goal is to one day realize photochemical recycling of traditional plastics with only sunlight. “Then you don’t need any other energy source, how cool would that be?” Eisenreich’s chemical breakthrough is therefore not only shining new light on plastic recycling, but also on his entire field. “This is not just a new material. It’s a new way forward.”