About 25 years ago, scientists predicted the existence of a glass phase whose building blocks are no linear molecular chains but ring-shaped polymers. When these ring molecules thread into each other, they restrict each other’s movement. Since it would take a very long time for the rings to unthread solely through thermodynamic fluctuations, this structure behaves de facto like a glass. However, such structures have never been observed in experiments. Simulations showed that such a state could only be achieved by conditions that are difficult to achieve, such as artificially freezing the rings.
Jan Smrek, University of Vienna, Austria, and Max Planck Institute for Polymer Research, Mainz, Germany, and colleagues have used simulations to make individual ring segments more mobile and were thus able to observe the active topological glass state for the first time. The stronger the fluctuations of the ring segments were, the more the ring molecules became entangled in each other. As a result, the material became altogether firmer and changed to the glass state.
Making the rings locally more mobile could be achieved by introducing molecular motors. The researchers selectively set segments of the polymer chains in motion by locally increased temperatures. An alternative is the synthesis of rings containing segments with increased light absorption.
According to the researchers, the first applications of the new material could, for example, be a liquid material with reversible glazing when exposed to light.
- Active topological glass,
Jan Smrek, Iurii Chubak, Christos N. Likos, Kurt Kremer,
Nature Communications 2020.