Researchers at the Lawrence Berkeley National Laboratory have uncovered a hidden phase transition between liquid and solid states in amorphous materials like plastic and glass, according to an article from the Berkeley Lab. Unlike crystalline materials that solidify upon cooling, these amorphous materials maintain a disordered, supercooled liquid state until a specific temperature is reached, causing them to become extremely viscous and solid-like. This temperature marks the onset of rigidity, separating supercooled liquids from normal ones.
The team used theory, computer simulations and prior experiments to explain this behavior. They likened localized particle movements, known as excitations, in supercooled liquids to defects in crystalline solids. As the temperature of the supercooled liquid rose, these defects transitioned from bound to unbound pairs. This change caused the loss of rigidity, making the liquid behave like a regular liquid.
“Our theory predicts the onset temperature measured in model systems and explains why the behavior of supercooled liquids around that temperature is reminiscent of solids even though their structure is the same as that of the liquid,” said Kranthi Mandadapu, a staff scientist in Berkeley Lab’s Chemical Sciences Division and professor of chemical engineering at the University of California, Berkeley, who led the work which was published in PNAS.
The researchers believe their findings have implications for various fields, such as medical devices, drug delivery and additive manufacturing. This newfound understanding of the transition from a supercooled liquid to a normal liquid, akin to melting, could enable the development of new amorphous materials with controlled properties. The study contributes to a deeper comprehension of the intricate dynamics that set supercooled liquids apart from typical liquids, shedding light on a long-standing mystery in materials science.
