Chinese researchers develop “self-recycling” polymers for next-gen plastics

Scientists have developed a “novel polymer class” called polydithiourethanes (PDTUs) with covalent bonds that facilitate “self-recycling” — the reprocessing of polymer networks.

The team based at Zhejiang University in Hangzhou, China, found that PDTU’s bonds can undergo dissociation under mild conditions without the need for a catalyst, enabling efficient reprocessing.

Dr Ning Zheng, the study’s principal investigator, says: “Our work on aromatic PDTUs represents a significant milestone in sustainable polymer science. By harnessing the inherent dynamism of dithiocarbamate bonds, we have created polymers that can self-recycle without sacrificing performance.”

“This represents a vital step toward next-generation plastics that significantly reduce environmental impact while maintaining utility.”

Reprocessing without a catalyst

The study, published in the Chinese Journal of Polymer Science, focuses on the synthesis and properties of PDTUs, a novel polymer class that utilizes aromatic dithiocarbamate linkages — these are dynamic covalent bonds with notable adaptability.

According to the scientists, these dynamic bonds allow the polymer network to dissociate and reassemble without the need for a catalyst, such as heating. Reprocessing under such “milder” conditions improves efficiency while retaining the polymer’s mechanical properties. 

The research team conducted extensive testing and demonstrated that PDTUs have high gel fractions and can therefore withstand rigorous thermal and mechanical stress and ensure durability in real-world applications.

The scientists say that the bond dissociation and network reconfiguration mechanism point to the material’s “robustness and transformative potential” for the plastics industry.

The PDTU rreprocessing timeline (Image credit: Zhejiang University).

The experiment 

For the synthesis of PDTU, the researchers weighed and mixed the chemicals 2,2’-(1,2-ethyldioxy) diethyl mercaptan (DODT), diethylene glycol divinyl ether (DGDV) and benzoin dimethyl ether (DMPA), and exposed them to UV radiation for 180 seconds. 

Afterward, the scientists added two organic compounds and a reagent to the mixture and stirred it well. The mixture was transferred to an aluminum dish, sealed with aluminum foil and subjected to thermal curing at 70 degrees Celsius for six hours. After the complete reaction, it underwent vacuum drying at the same temperature for 12 hours.

At the end of the process, the team obtained a yellow transparent film — a synthesis of materials with varying monomer contents.

This resulting polymer has the ability to self-reprocess. The PDTU sample was initially fragmented into particles with a dimension of 1 mm. These particles were subjected to hot pressing in a mold at a temperature of 130 degrees Celsius under a pressure of 4 MPa for 30 minutes.

The reformed polymer particles were then allowed to cool slowly at room temperature for 24 hours, which resulted in the “complete association of dithiocarbamate bonds.”

Scientists in Europe are also working to develop polymers with “self-healing” properties. A research team in the UK recently presented its “self-healing” plastic with glue-like properties, allowing the material to repair itself after being damaged. Scientists in Germany created bio-based and biodegradable mineral plastics using a natural biopolymer.

Last year, researchers in Japan introduced a “radical chain reaction method” to recycle and detoxify plastic waste.