The polymers that make up synthetic materials need time to de-stress after processing, researchers said. A new study has found that entangled, long-chain polymers in solutions relax at two different rates, marking an advancement in fundamental polymer physics. The findings will provide a better understanding of the physical properties of polymeric materials and critical new insight to how individual polymer molecules respond to high-stress processing conditions.
The study, published in the journal Physical Review Letters, could help improve synthetic materials manufacturing and has applications in biology, mechanical and materials sciences as well as condensed matter physics.
“Our single-molecule experiments show that polymers like to show off their individualistic behavior, which has revealed unexpected and striking heterogeneous dynamics in entangled polymer solutions,” said co-author Charles Schroeder, a professor of chemical and biomolecular engineering and faculty member of the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign. “The main goal of our research is to understand how single polymers – acting as individuals – work together to give materials macroscopic properties such as viscosity and toughness.”
Using a technique called single-molecule fluorescence microscopy, researchers can watch – in real time – as individual polymer molecules relax after the stretching, pulling and squeezing of the manufacturing process. “Imagine looking into a bowl of cooked spaghetti and watching the motion of a single noodle as the bowl is mixed,” Schroeder said.
“We found that the polymers exhibit one of two distinct relaxation modes,” said co-author and graduate student Yuecheng (Peter) Zhou. “One group of polymers relaxed via a single decaying exponential rate and the other group showed a two-phase process. That second population undergoes a very quick initial retraction followed by a slow relaxation. The existence of two different molecular populations was unexpected and not predicted by classical theory.”
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