Confined water vitrification

Water, a substance so familiar in our daily lives, harbours complexities that continue to intrigue scientists. One such enigma is the behaviour of water when it transforms into a glass-like state, known as vitrification, especially under confinement. A recent study ¹ delves into this phenomenon, shedding light on the intricate nature of confined water vitrification and its glass transition.

Vitrification and the glass transition

Typically, when liquids cool, they crystallize, forming structured, repeating patterns. However, under certain conditions, some liquids bypass crystallization, becoming amorphous solids—a process termed vitrification. These amorphous solids, or glasses, lack the long-range order of crystals but behave mechanically like solids. The temperature at which a liquid becomes glassy is the glass transition temperature (Tg).

Water’s vitrification is particularly intriguing due to its propensity to crystallize easily. Avoiding crystallization requires rapid cooling or confinement in tiny spaces, preventing the formation of ice crystals. Understanding water’s glassy state is vital, as it influences various fields, from cryopreservation to atmospheric science.

Probing confined water

The study in focus investigates water confined within nanometre-scale pores of materials like silica. Confinement alters water’s properties, offering a unique environment to study its glass transition without crystallization.

Researchers employed advanced techniques, including calorimetry and spectroscopy, to observe water’s behaviour within these confined spaces. Calorimetry measures heat flow, providing insights into phase transitions, while spectroscopy examines molecular dynamics.

The researchers found multiple glass transition temperatures. Unlike bulk water, which has a single Tg, confined water exhibits multiple glass transition temperatures. This suggests the presence of different amorphous states within the confined spaces, each with distinct dynamics. Confined water displays varying molecular mobility across different regions. Some water molecules exhibit rapid movement, while others remain relatively immobile, indicating a heterogeneous dynamic landscape.

Interestingly, the size of the confining pores significantly impacts water’s vitrification. Smaller pores tend to suppress crystallization more effectively, stabilizing the glassy state over a broader temperature range.

Surprising implications

As liquid water is present almost everywhere, from cells to the atmosphere, these observations have profound implications in very different contexts. For example, in cryopreservation: Understanding confined water’s glass transitions can enhance cryopreservation techniques for biological samples, minimizing ice crystal formation that can damage cells.

Or in climate science, as atmospheric water often exists in confined states, such as within aerosols. Insights into its vitrification behaviour can improve climate models by accurately representing cloud dynamics and precipitation processes.

Finally, the impact on materials science is undeniable. The findings can inform the design of materials where water’s behaviour is crucial, such as in fuel cells and desalination membranes.

The study illuminates the complex nature of water’s glass transition under confinement, revealing behaviours distinct from bulk water. These insights not only deepen our fundamental understanding of water but also pave the way for advancements in various scientific and technological domains.

Author: César Tomé López is a science writer and the editor of Mapping Ignorance

Disclaimer: Parts of this article may have been copied verbatim or almost verbatim from the referenced research paper/s.