Self-assembly of defined core-shell ellipsoidal particles at liquid interfaces.

Area of Science:

• Colloid and surface science
• Materials science
• Soft matter physics

Background:

• Anisotropic particles at liquid interfaces self-assemble via capillary interactions.
• Quadrupolar interactions favor either tip-to-tip or side-to-side configurations.
• Predicting and controlling self-assembly structures remains a challenge.

Purpose of the Study:

• To investigate the effect of polymer shells on the interfacial self-assembly of ellipsoidal particles.
• To determine how particle geometry and shell properties influence self-assembly configurations.
• To develop a method for controlling the self-assembly of anisotropic particles.

Main Methods:

• Fabrication of core-shell ellipsoidal particles with controlled aspect ratios and shell thicknesses using thermo-mechanical stretching.
• Interfacial self-assembly experiments to observe structural formation.
• Monte Carlo simulations and theoretical calculations to map the phase diagram of preferred structures.

Main Results:

• Unshelled ellipsoidal particles consistently form side-to-side chain-like assemblies.
• Core-shell ellipsoidal particles transition from tip-to-tip flower-like to side-to-side structures with increasing aspect ratio.
• The critical aspect ratio for this transition is modulated by shell thickness.

Conclusions:

• Polymer shells can effectively tune the capillary interactions of ellipsoidal particles at liquid interfaces.
• Engineering particle aspect ratio and shell thickness allows for deterministic control over self-assembly configurations.
• This work provides a pathway for designing and realizing specific structures from anisotropic particles.