The true nature of glass has been a mystery even till today. The true nature of glass is confusing and remains a mystery.
Generally, when material changes its state from liquid to a solid-state, the molecules form a crystal pattern but this doesn’t occur with glass. In glass, the particles freeze completely before crystallization happens.
Study at the University of Konstanz has just added another layer of complexity to the glass conundrum. The research team used a model system involving suspensions of tailor-made ellipsoidal colloids to discover a new state of matter, liquid glass, where individual particles can move yet unable to rotate. This complex behaviour has not previously been observed in bulk glasses.
We know colloidal suspensions are mixtures that contain solid particles which, at micrometre size, are bigger than atoms and consequently appropriate to examination with optical microscopy. These are popular among glass transitions as they include many phenomena in other glass-forming materials.
Until now, many experiments involving colloidal suspensions have relied on spherical colloids. However, a major part of natural and technical systems are comprised of non-spherical particles.
Scientists created small plastic particles, stretching and cooling them until they achieved their ellipsoid forms and then placed them in a suitable solvent.
Zumbusch, a physical chemistry professor and senior author of the study, said that the distinct shapes of the particles gave rise to new kinds of complex behaviours.
Scientists change the particle concentrations in suspensions and tracked both the particles.
Zumbusch added that 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.
Liquid glass has been termed because of the clusters mutually obstructing each other and mediating characteristic long-range spatial correlations. These prevent the formation of a liquid crystal, which would be the globally ordered state of matter expected from thermodynamics.
Two competing glass transitions were observed. A regular phase transformation and a nonequilibrium phase transformation which were found to be interacting with each other.
Matthias Fuchs, professor of soft condensed matter theory at the University of Konstanz, said that this was an interesting point. These experiments provided the evidence for interplay between critical fluctuations and glassy arrest that the scientific community has been after for quite some time.
The results suggest that similar dynamics may be at work in other glass-forming systems and may thus help shed light on the behaviour of complex systems and molecules ranging from the tiny (biological) to the enormous (cosmological). It also potentially impacts the development of liquid crystalline devices.
Journal Reference:
Jörg Roller, Aleena Laganapan, Janne-Mieke Meijer, Matthias Fuchs, Andreas Zumbusch: Observation of liquid glass in suspensions ellipsoidal colloids, PNAS, 4 January 2021. URL: DOI: 10.1073/pnas.2018072118
Press Release: University of Konstanz
