Freedericksz transition in polymer-stabilized nematic liquid crystals

Area of Science:

• Materials Science
• Polymer Chemistry
• Condensed Matter Physics

Background:

• Polymer-stabilized liquid crystals combine properties of polymers and liquid crystals.
• The Freedericksz transition is a key phenomenon in liquid crystal physics, involving reorientation under an electric field.
• Controlling liquid crystal orientation with polymer networks is crucial for display technologies.

Purpose of the Study:

• To construct and investigate polymer-stabilized nematic liquid crystals.
• To study the effect of polymer networks on the Freedericksz transition.
• To develop a theoretical model for understanding liquid crystal-polymer interactions.

Main Methods:

• Photopolymerization of diacrylate monomers in the nematic phase to form polymer networks.
• Experimental measurement of capacitance changes during the Freedericksz transition under applied voltage.
• Development of a 2D theoretical model representing polymer networks as parallel cylinders.

Main Results:

• The dispersed polymer network profoundly affected the Freedericksz transition.
• A higher threshold voltage was observed with shorter interpolymer network distances.
• The theoretical model, fitted to experimental data, indicated polymer cylinder diameters of submicrons.
• Significant amounts of liquid crystal were found to be trapped within the polymer cylinders.

Conclusions:

• Polymer network structure dictates liquid crystal orientation and transition behavior.
• The study provides insights into the fundamental interactions between liquid crystals and polymer networks.
• The findings have implications for designing advanced liquid crystal materials and devices.