CHICAGO, May 17 (Xinhua) -- Recyclable plastics that contain ring-shaped polymers may be a key to developing sustainable synthetic materials, as researchers at the University of Illinois (UI) have identified a mechanism called "threading" that takes place when a polymer is stretched in a new study.

According to a UI news release on Friday, UI researchers examined the flow dynamics of DNA-based ring and linear polymer solutions to sort out clues about how synthetic polymers interact during processing in the study.

They stretched and squeezed polymers, causing them to flow and allowing direct observation of the behavior of individual molecules using single-molecule fluorescence microscopy.

Using a combination of direct single-molecule observations and physical measurements, the researchers concluded that the changes in shape of the ring polymers occur because linear molecules thread themselves through the ring molecules when stressed, causing the ring shape to fluctuate under fluid flow.

"There is a fluctuation in the shape of the ring polymers and this depends on the concentration of linear polymers in the solution," said Yuecheng Zhou, a UI graduate student and lead author of the study. "We do not see this behavior in pure solutions of ring or linear polymers, so this tells us that something unique is happening in mixed solutions."

"We observed this behavior even when there is a very low concentration of linear polymers in the mix," Zhou added. "This suggests that it only takes a very minute level of contamination to cause this phenomenon."

How these observations will translate into further development of sustainable consumer plastics remains unclear, the researchers said. However, this insight into the fundamental molecular properties of mixed-polymer solutions may lead to new processing methods for sustainable polymer materials.

"To make pure ring polymer plastics a reality, we need to understand both mixed and pure solutions at a fundamental level," said Charles Schroeder, a UI chemical and biomolecular engineering professor and the study's co-author. "Once we can figure out how they work, then we can move on to synthesizing them and ultimately how to use them in sustainable consumer plastics."

The findings have been published in the journal Nature Communications.