This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Before diving into the mystery of glass, theoretical physicist Corentin Laudicina takes us back to high school physics for a moment. Although he has spent years studying exactly what happens in a material during the glass transition, he also understands that his research is not the easiest thing to explain off the cuff at the cafeteria table.
According to school textbooks, matter can exist in three different states: gas, liquid and solid. Think of water vapor, liquid water and ice. The molecules that make up the material are the same, but the way they can move differs greatly, Laudicina explains.
He pulls out his dissertation and shows a figure from the introductory chapter. "The higher the temperature, the more freely the molecules can move. In a solid, they are arranged in a crystal lattice—in a fixed position, at a fixed distance from one another—but in a liquid, they can move without having a fixed position relative to each other.
In the gas phase, those movements are even freer." But in addition to these three familiar phases, there is also a fourth phase that a material can enter when it is cooled quickly enough: the glass phase. And there is something unusual about it, Laudicina explains. "The strange thing about a material in the glass phase is that it behaves like a solid, while its internal structure is more like that of a liquid.
There is no rigid crystal lattice, but rather a disordered structure. So, in a sense, a drinking glass is liquid." To better understand the glass phase, Laudicina and his colleagues from the Soft Matter & Biological Physics group study what happens when a liquid is cooled. They focus on a material's viscosity, or, in other words, how thick and slow-flowing it is.
"As the temperature drops, the molecules become progressively less able to move. Around the glass transition, however, the viscosity increases extremely rapidly—much faster than you would expect. And yet the material's internal structure barely changes.
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