Low-Temperature Structural Study of Smectic C_A* Glass by X-ray Diffraction

Area of Science:

• Materials Science
• Condensed Matter Physics
• Crystallography

Background:

• Liquid crystals exhibit unique phases between solid and liquid states.
• The smectic C_A* phase is a complex liquid crystalline phase with tilted molecular ordering.
• Understanding the glassy state of liquid crystals is crucial for their technological applications.

Purpose of the Study:

• To investigate the structural and electronic properties of a smectic C_A* liquid crystal glass.
• To determine characteristic distances and electron density profiles within the smectic C_A* glass.
• To analyze the helical ordering and its temperature dependence below the glass transition temperature.

Main Methods:

• X-ray diffraction was employed to study the liquid crystalline compound over a temperature range of 18-298 K.
• Electron density profiles were inferred and compared with density functional theory (DFT) calculations.
• Selective reflection of visible light was observed to investigate helical ordering.

Main Results:

• Characteristic distances and specific volume within the smectic C_A* phase were determined.
• Electron density profiles were consistent with DFT calculations.
• Slow temperature-dependent changes were observed in smectic layer spacing, intermolecular distances, and electron density below the glass transition temperature.
• The helix pitch and short-range order within smectic layers remained relatively constant in the glassy state.

Conclusions:

• The glassy state of the smectic C_A* liquid crystal exhibits slow structural evolution below the glass transition temperature.
• Molecular ordering and helical structure show stability within the glassy state.
• The study provides insights into the behavior of liquid crystal glasses, relevant for materials science and condensed matter physics.