4/30/2023 0 Comments Liquid glass![]() ![]() The team made this discovery in a model system of colloidal suspensions. Essentially, the atoms can move but aren’t able to rotate. In the new study, the researchers discovered a form of glass where the atoms exhibit a complex behavior that’s never been seen in bulk glass before. ![]() That’s not the case with glass though: its atoms “freeze” in their disordered state. Normally when a substance transitions from a liquid to a solid, the formerly free-flowing atoms line up into a rigid crystal formation. But that’s not technically true – glass is an amorphous solid. It’s a persistent fallacy that glass already is a liquid, spread by misinformed high school teachers and tour guides. Now scientists at the University of Konstanz have identified a new state of matter called liquid glass, which has some unusual properties. PNAS 118 (3): e2018072118 doi: 10.1073/pnas.Mundane as it may seem, glass is a surprisingly mysterious material. Observation of liquid glass in suspensions of ellipsoidal colloids. ![]() The discovery is reported in a paper published in the Proceedings of the National Academy of Sciences. “It also potentially impacts the development of liquid crystalline devices.” “The results further suggest that similar dynamics may be at work in other glass-forming systems and may thus help to shed light on the behavior of complex systems and molecules ranging from the very small (biological) to the very big (cosmological).” ![]() “A prediction of liquid glass had remained a theoretical conjecture for twenty years.” “Our experiments provide the kind of evidence for the interplay between critical fluctuations and glassy arrest that the scientific community has been after for quite some time.” “This is incredibly interesting from a theoretical vantage point,” said co-senior author Professor Matthias Fuchs, a researcher in the Department of Physics at the University of Konstanz. The team observed two glass transitions - a regular phase transformation and a nonequilibrium phase transformation - interacting with each other. “These prevent the formation of a liquid crystal which would be the globally ordered state of matter expected from thermodynamics.”Ĭomputer rendered 3D reconstruction of a subset of a sample volume with the red-green-blue value of the color indicating the particle orientations. “What we’ve termed liquid glass is a result of these clusters mutually obstructing each other and mediating characteristic long-range spatial correlations.” “At certain particle densities orientational motion froze whereas translational motion persisted, resulting in glassy states where the particles clustered to form local structures with similar orientation,” Professor Zumbusch said. Using confocal laser scanning microscopy, the researchers recorded the temporal development of the 3D positions and orientations for more than 6,000 ellipsoidal particles. “Due to their distinct shapes our particles have orientation, as opposed to spherical particles, which gives rise to entirely new and previously unstudied kinds of complex behaviors,” Professor Zumbusch explained. In their experiments, Professor Zumbusch and co-authors focused on ellipsoidal polymethylmethacrylate colloids. The recent interest in synthetic colloids as material building blocks, however, has led to the development of a multitude of novel techniques for the synthesis of colloidal particles with specific geometries and interactions.” “To date, most experiments have been done using spherical colloids. “When the density of such suspensions is increased to high volume fractions, often their structural dynamics are arrested in a disordered, glassy state before they can form an ordered structure.” “Suspensions of colloidal particles are widely spread in nature and technology and have been studied intensely over more than a century,” said co-senior author Professor Andreas Zumbusch from the Department of Chemistry at the University of Konstanz and his colleagues. Inset shows a confocal microscopy image, highlighting the core-shell structure. Scanning electron microscope image of the ellipsoidal colloids. ![]()
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