Photoisomerization-controlled phase segregation in a submicron confined azonematic liquid crystal

Area of Science:

• Materials Science
• Physical Chemistry
• Supramolecular Chemistry

Background:

• Photoisomerizable liquid crystals exhibit unique phase behaviors.
• Confinement effects in porous materials significantly alter material properties.
• Understanding phase diagrams is crucial for designing advanced materials.

Purpose of the Study:

• To investigate the phase segregation of photoisomerizable liquid crystal diheptylazobenzene (7AB) within Anopore membranes.
• To dynamically control the composition of trans-7AB and cis-7AB mixtures.
• To determine the temperature-concentration phase diagram of 7AB in confined geometries.

Main Methods:

• Deuteron nuclear magnetic resonance (NMR) spectroscopy was employed.
• Photoisomerization was induced using UV illumination (trans-to-cis).
• Thermal backisomerization (cis-to-trans) was utilized for dynamic control.

Main Results:

• Phase segregation behavior of 7AB in Anopore membranes was successfully studied.
• Dynamic control over the trans-7AB and cis-7AB concentrations was achieved.
• The temperature-concentration phase diagram was determined through comparative analysis across different geometries (bulk, planar, confined).

Conclusions:

• The study elucidates the phase segregation of photoisomerizable liquid crystals under confinement.
• Dynamic control via photoisomerization offers a novel approach to manipulate material composition.
• The determined phase diagram provides critical insights for the application of such systems.