Orientational order and finite strain in nematic elastomers

Area of Science:

• Materials Science
• Polymer Physics
• Soft Matter Physics

Background:

• Nematic elastomers undergo substantial spontaneous shape changes when transitioning from an isotropic to a nematic phase.
• Understanding these large deformations is crucial for developing advanced materials with tunable properties.

Purpose of the Study:

• To develop a nonlinear, variational theory for nematic elastomers that couples orientational order and elastic deformation.
• To investigate how elastic properties influence the isotropic-nematic transition temperature and the resulting spontaneous shape changes.

Main Methods:

• Formulation of a free-energy functional comprising nematic and elastic contributions.
• Minimization of the free-energy functional to model finite deformations and phase transitions.
• Analysis of the interplay between mesogenic unit interactions and polymer chain stretching.

Main Results:

• The developed theory accurately describes large, reversible, spontaneous shape changes in nematic elastomers.
• Elastic deformation was shown to significantly impact the isotropic-nematic transition temperature.
• The magnitude of spontaneous deformation was quantified for various material parameters.

Conclusions:

• The theory provides a robust framework for understanding and predicting the behavior of nematic elastomers.
• This work offers insights into designing materials with controlled shape-changing capabilities.
• The model encompasses soft elasticity as a specific instance but is broadly applicable.