Prediction of disclinations in nematic elastomers

Area of Science:

• Materials Science
• Polymer Physics
• Soft Matter Physics

Background:

• Nematic elastomers exhibit unique mechanical and optical properties due to anisotropic polymer networks.
• Understanding the behavior of these materials under deformation is crucial for designing advanced applications.

Purpose of the Study:

• To develop a theoretical framework for uniaxial nematic elastomers with variable asphericity.
• To investigate the formation and characteristics of an isotropic core in these materials under extension.

Main Methods:

• Formulation of a theory for uniaxial nematic elastomers.
• Numerical solutions of differential equations for isochoric extension of a cylinder.
• Analysis of asphericity, molecular coil shapes, and free-energy density.

Main Results:

• Existence of an isotropic core with spherical polymer coils at the cylinder axis for large extensions.
• A transition layer where asphericity rapidly changes and free-energy density drops.
• Anisotropic regions with ellipsoidal polymer coils oblate about the radial direction.

Conclusions:

• The theory predicts a preference for disclinated states in nematic elastomers.
• The boundary of the isotropic core is linked to a significant drop in free-energy density.
• The predicted core size aligns with experimental observations in liquid crystal melts.