Authors of the publication (from left to right).: Susanne Schwanz, Dr Thomas Emmler, Dr Michael Schroeter, Phannaro Nhem, Prof Francesca M. Toma, Dr Manfred Gossen, Dr Katarzyna Polak-Krasńa, Dr Navid Khani, Yiduo Zhou, Dr Weiwei Wang. Photo: Marcel Schwickerath

Polystyrene is used in protective packaging for televisions and electronic devices, in decorative and skirting boards for interior construction, and in Petri dishes. It is one of the world's most important plastics, with nearly 20 million tonnes produced each year. The material is predominantly derived from crude oil and is rarely recycled. Virgin polystyrene is often cheaper than recycled material, meaning that used products are typically incinerated or sent to landfills. Like many other plastics, polystyrene is highly resistant to degradation in the environment.

Researchers have now developed a more sustainable version of polystyrene. “The combination of renewable feedstocks, reduced energy consumption, and improved recyclability represents a major step forward,” says doctoral researcher Phannaro Nhem, who is currently pursuing his PhD under the supervision of Prof Francesca Toma, Director of Hereon’s Institute of Functional Materials for Sustainability. The project also involved researchers from BTU Cottbus-Senftenberg, Freie Universität Berlin, and Helmut Schmidt University in Hamburg.

The petri dishes meet the required quality standards. Photo: Hereon/Marcel Schwickerath

The team also incorporated the compound DOT into the material. These DOT molecules act as deliberately integrated breaking points within the polymer network, allowing the material to be chemically broken down into smaller fragments at the end of its life cycle. “Unlike conventional polystyrene, our material can be fragmented into small pieces,” says Nhem. These smaller fragments can subsequently be further processed chemically. Bacteria are also capable of metabolizing the fragments, whereas they cannot degrade the tightly cross-linked structure of conventional polystyrene.

“The new polymer was developed according to the design-for-degradation principle, meaning it is engineered for controlled breakdown at the end of its service life,” adds Francesca Toma. “This opens up a pathway for polystyrene towards closed material cycles and a circular economy.” Initial tests have shown that the material can be processed using conventional injection-molding equipment. Using their current laboratory-scale setup, the researchers produced miniature Petri dishes approximately the size of a one-euro coin. In the future, however, a wide range of applications could be envisaged. Preliminary studies with human stem cells also indicate that the material is biocompatible and performs just as well as commercially available polystyrene for cell culture applications.