A Landau-de Gennes theory for hard colloidal rods: Defects and tactoids

Area of Science:

• Physics
• Soft Matter Physics
• Colloidal Science

Background:

• Hard colloidal rods exhibit complex phase behaviors, including isotropic-nematic transitions.
• Understanding these transitions is crucial for materials science and nanotechnology.
• Existing theories may not fully capture the nuances of rod-like particle interactions.

Purpose of the Study:

• To construct a phenomenological Landau-de Gennes theory for hard colloidal rods.
• To describe the isotropic-nematic phase transition and interface.
• To apply the theory to various defect structures and confinement scenarios.

Main Methods:

• Order parameter expansion of the chemical-potential dependent grand potential.
• Fitting theory coefficients to Onsager theory results.
• Applying the developed theory to calculate defect properties and droplet formation.

Main Results:

• Accurate description of the isotropic-nematic phase transition, including density jumps.
• Successful modeling of the isotropic-nematic planar interface.
• Calculations revealed isotropic core size in hedgehog defects and density dependence of linear defects in confinement.

Conclusions:

• The phenomenological Landau-de Gennes theory provides a robust framework for hard colloidal rod systems.
• The theory successfully predicts key phase behaviors and defect structures.
• This work advances the understanding of anisotropic particle systems and their applications.