Temperature-Driven Anchoring Transitions at Liquid Crystal/Water Interfaces

Area of Science:

• Materials Science
• Soft Matter Physics
• Physical Chemistry

Background:

• Controlling liquid crystal (LC) molecular anchoring at interfaces is vital for LC phase organization and applications.
• Traditional methods for triggering anchoring transitions, like surfactant adsorption, are slow and irreversible.
• Liquid crystal shells offer enhanced sensitivity to interfacial effects compared to droplets.

Purpose of the Study:

• To investigate a novel, rapid, and reversible method for controlling molecular anchoring in liquid crystal shells.
• To explore the use of temperature changes near the clearing point to induce anchoring transitions.
• To study the structural transformations and defect formation during these temperature-induced anchoring switches.

Main Methods:

• Utilized 4-cyano-4'-pentylbiphenyl (5CB) liquid crystals and dilute aqueous solutions of polyvinyl alcohol (PVA).
• Investigated anchoring transitions on both flat suspended films and spherical liquid crystal shells.
• Employed quasi-static temperature increases near the 5CB clearing point to trigger molecular reorientation.

Main Results:

• Demonstrated temperature-induced, instantaneous reorientation of 5CB molecules from parallel to perpendicular anchoring at the interface with PVA solutions.
• Observed that PVA's local disordering effect precedes the bulk 5CB phase transition, enabling controlled anchoring changes.
• Characterized structural transformations and defect stabilization, noting dependence on film topology.
• Showcased the ability to transform polydisperse nematic shells into a monodisperse population of bivalent shells.

Conclusions:

• Temperature control near the clearing point provides a rapid and reversible method to switch liquid crystal anchoring.
• This technique allows for simultaneous influence on both interfaces of liquid crystal films.
• The method offers potential for precise control over liquid crystal shell populations, enabling the creation of monodisperse bivalent shells.