Patterned surface anchoring of nematic droplets at miscible liquid-liquid interfaces

Area of Science:

• Soft Matter Physics
• Materials Science
• Colloid Science

Background:

• Nematic liquid crystals (LCs) exhibit diverse internal configurations and topological defects.
• Surface anchoring conditions (homeotropic vs. tangential) dictate LC droplet behavior.
• Understanding LC droplet behavior at liquid-liquid interfaces is crucial for materials design.

Purpose of the Study:

• To investigate the internal configurations of nematic LC droplets at aqueous-glycerol interfaces.
• To elucidate the role of compositional gradients in dictating surface anchoring and defect formation.
• To explore new pathways for controlling LC droplet symmetry and optical properties.

Main Methods:

• Sedimentation of LC droplets (10-50 μm diameter) from SDS solutions onto glycerol interfaces.
• Observation of internal configurations and topological defects using microscopy.
• Photo-polymerization to preserve configurations and systematic variation of sedimentation time.
• Computational simulations using Landau-de Gennes free energy minimization.

Main Results:

• Observed abrupt transition from homeotropic to tangential anchoring on LC droplet surfaces.
• Identified distinct LC droplet configurations and topological defects (point defects, boojums, disclination loops) based on the fraction of tangential anchoring.
• Demonstrated time-dependent changes in anchoring and configuration, consistent with compositional gradients.
• Formation of 'Janus-like' particles with mixed anchoring properties.

Conclusions:

• Compositional gradients at miscible liquid-liquid interfaces induce patterned surface anchoring on LC droplets.
• This phenomenon leads to a rich variety of LC droplet configurations and topological defects not seen in bulk.
• Translocation across interfaces provides new pathways to transition between distinct LC droplet configurations.