Isotropic-to-cholesteric transition in liquid crystal elastomers.

Area of Science:

• Materials Science
• Soft Matter Physics
• Polymer Science

Background:

• Liquid crystal elastomers (LCEs) exhibit unique phase transitions and mechanical properties.
• Spontaneous strain in LCEs is driven by the transition to the nematic phase.
• Elastic energy, particularly Frank elastic energy, plays a crucial role in LCE behavior.

Purpose of the Study:

• To investigate the interplay between spontaneous elongation and elastic energy minimization in LCEs.
• To characterize the different structural states (transverse cholesteric, uniformly aligned, conical) adopted by LCEs.
• To analyze the transition lines and critical points between these states.

Main Methods:

• Theoretical modeling of LCE behavior.
• Analysis of Frank elastic energy contributions (bend, twist).
• Determination of phase transition lines and critical exponents.

Main Results:

• Identified transverse cholesteric and uniformly aligned states as extremes of Frank energy reduction.
• Described intermediate conical states with combined bend and partial twist energy satisfaction.
• Mapped first-order and second-order transition lines dependent on chain anisotropy and elastic constants.
• Provided analytical forms for director variation and multicritical point dependence on Frank constants.

Conclusions:

• LCEs can adopt diverse structures to minimize elastic energy during spontaneous elongation.
• Material properties like anisotropy and elastic constants dictate the nature and stability of these structures.
• The study provides a comprehensive theoretical framework for understanding LCE phase transitions and mechanical responses.