Liquid crystals are fascinating materials that exhibit properties of both liquids and crystals. They consist of long, rod-shaped molecules that can align themselves in a variety of ways, giving rise to different optical properties. Liquid crystals are used in a wide range of applications, including displays, lasers, and sensors.

One of the most important properties of liquid crystals is their ability to form ordered structures. This ordering is essential for the materials' optical properties and their ability to function as displays and other devices.

How exactly order first appears in liquid crystals has been a topic of debate and research for decades. Now, a team of researchers from the University of Colorado Boulder and the National Institute of Standards and Technology (NIST) has used a powerful X-ray technique to capture the first direct images of the ordering process, a discovery that could lead to new and improved liquid-crystal-based devices.

The study was published in the journal Nature Communications.

The researchers used a technique called X-ray photon correlation spectroscopy (XPCS) to study the ordering process in liquid crystals. XPCS is a technique that allows researchers to measure the dynamics of materials at the nanoscale.

In their experiments, the researchers heated a sample of liquid crystal to a temperature just below the point at which it would transition from a liquid to a crystalline phase. They then used XPCS to measure the fluctuations in the density of the liquid crystal molecules as they began to order themselves into a crystalline structure.

The researchers' XPCS measurements revealed that the ordering process in liquid crystals occurs in two steps. In the first step, the molecules form small, ordered clusters that are randomly distributed throughout the liquid. In the second step, these small clusters grow and merge together, eventually forming a single, large, ordered crystal.

The researchers believe that the formation of clusters prior to the formation of a single crystal is due to the fact that the liquid crystal molecules have a strong tendency to align themselves with their neighbors. This tendency to align leads to the formation of small, ordered clusters, which then act as nucleation sites for the growth of the single crystal.

The researchers' findings have important implications for the design and development of liquid-crystal-based devices. By understanding how order first appears in liquid crystals, researchers can better control the optical properties of these materials and design devices that have improved performance.

References

The paper can be found here: https://www.nature.com/articles/s41467-023-36317-0

An accessible news article from the University of Colorado, Boulder can be found here: https://www.colorado.edu/today/2023/03/14/ordering-liquid-crystals-revealed