Degenerate conic anchoring and colloidal elastic dipole-hexadecapole transformations.

Area of Science:

• Soft Matter Physics
• Materials Science
• Colloid Science

Background:

• Colloid-induced defect structures in liquid crystals depend on surface molecular orientation.
• Existing models explain dipole-like and quadrupole-like defects but not the elastic hexadecapole.
• The elastic hexadecapole was previously attributed to conic anchoring conditions.

Purpose of the Study:

• To fundamentally understand the elastic hexadecapole defect structure in nematic liquid crystals.
• To introduce and investigate a model for conic anchoring conditions.
• To explore the influence of preferred tilt angle on defect configurations and colloidal interactions.

Main Methods:

• Development of a model for conic anchoring within a Landau-de Gennes free energy functional.
• Investigation of defect structure evolution by systematically tuning the preferred tilt angle (θe).
• Experimental validation of theoretical predictions regarding defect configurations and transformations.

Main Results:

• The model predicts an elastic dipole whose stability diminishes with increasing preferred tilt angle.
• A transformation from dipole-like to hexadecapole-like defect structures was observed as the tilt angle varied.
• Experimental results confirmed the model's predictions of dipole stability decrease and dipole-hexadecapole transformation.

Conclusions:

• The preferred tilt angle is a critical parameter for controlling defect structures in colloids within nematic liquid crystals.
• The study provides a fundamental understanding of the elastic hexadecapole and its formation mechanism.
• Control over tilt angle offers new possibilities for designing self-assembled structures in liquid crystal-colloid systems.