Researchers at the Max Planck Institut für Struktur und Dynamik der Materie (MPSD) have made an unexpected discovery regarding the behavior of liquid glycerol. In their study published in the Proceedings of the National Academy of Sciences, the scientists observed that liquid glycerol exhibited a rubbery state instead of the expected viscous liquid behavior.
Using a pulsed laser, the researchers created rapidly expanding bubbles on the liquid’s surface in a vacuum. Surprisingly, the thin liquid envelope of the bubbles behaved like an elastic rubber balloon, capable of storing and releasing elastic energy. This elasticity dominating the flow behavior in a Newtonian liquid like glycerol had not been observed before and challenges existing understandings of liquid-glycerol interactions.
The observed elasticity persists over long timescales, making it potentially relevant for high-pressure micrometer-confined flows. The researchers suggest that the high straining rate and confined thickness of the bubble’s shell cause the individual glycerol molecules to form groups that collectively displace in a correlated manner, leading to the stabilization of the elastic state.
Understanding this unusual state could provide insights into collective excitations in disordered systems. The researchers also raise the question of whether similar effects are possible in other liquid substances. While glycerol bubbles were observed in a vacuum, performing similar experiments with water poses challenges due to its boiling point.
The research was conducted by the MPSD team and guest scientist Zhipeng Huang from the University of Duisburg-Essen. The discovery prompts a reconsideration of the correlations and differences between liquids and solids. Future investigations aim to explore the molecular interaction and structure of the transient bubble shell and whether this effect can be replicated in other liquids with different molecular interactions than glycerol.
Source: Max Planck Society