Random anisotropy nematic model: nematic-non-nematic mixture.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Chemical Physics

Background:

• Phase separation in liquid crystal mixtures is crucial for material properties.
• Disorder, particularly random anisotropy (RA), can significantly alter phase behavior.
• Understanding impurity effects on thermotropic liquid crystals is key.

Purpose of the Study:

• To investigate the impact of RA-type disorder on the phase separation of nematogen-non-nematogen mixtures.
• To model the interplay between orientational ordering and phase separation under disorder.
• To analyze the formation of domain-type structures in liquid crystal phases.

Main Methods:

• Combined phenomenological Landau-de Gennes and Flory-Huggins theories.
• Application of the Imry-Ma argument for domain pattern analysis.
• Theoretical modeling of disorder strength using the dimensionless parameter Lambda.

Main Results:

• Impurities induce RA disorder, enforcing orientational ordering in the paranematic phase.
• A domain-type structure (speronematic phase) forms in the low-temperature phase.
• RA field opposes phase separation, decreasing ordering differences with increasing Lambda.

Conclusions:

• The presence of RA disorder leads to complex phase-separated patterns.
• Orientational ordering enhances phase separation, but RA disorder counteracts this.
• The speronematic phase structure becomes more complex as disorder strength increases.