As accustomed as we are to glass, it is a surprisingly mysterious material. And now, a team of scientists from the University of Constance (Germany) has identified a new state of matter related to it: the so-called liquid glass, with some rather unusual properties.
“To date, most of the experiments have been done using spherical colloids. However, the recent interest in synthetic colloids as building blocks of materials has led to the development of a multitude of novel techniques for the synthesis of colloidal particles with specific geometries and interactions “, explains Andreas Zumbusch, co-author of the work published in the journal PNAS.
How did they do it?
Using a technique called confocal laser scanning microscopy and more than 6,000 ellipsoidal particles, the researchers discovered that ellipsoidal colloid suspensions of polymethylmethacrylate formed an unexpected state of matter, liquid glass, in which individual particles can move but cannot. rotate.
“Because of their different shapes, our particles have orientation, unlike spherical particles, leading to completely new and previously unstudied kinds of complex behavior,” explained Professor Zumbusch.
This new state seems to exist between a solid and a colloid (like a gel) : homogeneous mixtures with particles that are microscopic but are still larger than atoms and molecules (and therefore easier to study). The funny thing is that the scientists observed that, in the liquid glass, the colloids could move, but they could not rotate. They had more flexibility than glass molecules, but not enough to be compared to other materials. The particles were clogging each other inside the material!
Behavior not studied so far
“This is incredibly interesting from a theoretical point of view,” says Matthias Fuchs, professor of condensed soft matter theory at the University of Constance. “Our experiments provide the kind of evidence for the interaction between critical fluctuations and crystal arrest that the scientific community has been looking for for quite some time.”
Experts claim that the observed behavior comes from two competing glass transitions interacting with each other. Liquid glass had been predicted decades ago, and the new observation suggests that similar processes may be at work in other glass-forming systems. This prediction is no longer conjecture and “also has a potential impact on the development of liquid crystal devices,” the authors conclude. But there are still many unanswered questions.
Other states of matter
- Plasma, the form in which the gases contained inside fluorescent tubes or neon lights are presented.
- Bose-Einstein condensate, which we managed to create in space in 2020 and is formed by gas clouds of multiple atoms that behave as if they were one, sharing their quantum properties.
Referencia: Jörg Roller et al. 2021. Observation of liquid glass in suspensions of ellipsoidal colloids. PNAS 118 (3): e2018072118; doi: 10.1073/pnas.2018072118
