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Elastic response and Ward identities in stressed nematic elastomers
1Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 28, 2010
Summary
Nematic elastomers show a unique semisoft elastic response. This study reveals how their elastic moduli behave during strain, particularly vanishing shear moduli at plateau boundaries.
Area of Science:
- Materials Science
- Polymer Physics
- Soft Matter Physics
Background:
- Nematic elastomers display complex elastic behaviors under stress.
- A specific "semisoft" response is observed in elastomers with a fixed anisotropy direction (z) achieved through double cross-linking.
- This response features a distinctive stress-strain curve with an initial rise, a plateau, and a subsequent rise.
Purpose of the Study:
- To investigate the elastic response of semisoft elastomers under varying external strain.
- To derive general Ward identities for elastic moduli in these materials.
- To analyze the behavior of specific elastic moduli, particularly in relation to the semisoft plateau.
Main Methods:
- Exploration of elastic response as a function of applied strain.
- Derivation of general Ward identities for elastic moduli.
- Calculation of relevant elastic moduli using a simplified elastomer model.
Main Results:
- The elastic modulus associated with xz shear response vanishes at the edges of the semisoft plateau.
- Moduli related to shears perpendicular to the xz plane do not vanish at these boundaries.
- Model calculations confirmed the predictions derived from the general Ward identities.
Conclusions:
- The study provides a theoretical framework for understanding the elastic properties of nematic elastomers.
- Ward identities offer valuable insights into the vanishing shear modulus at the semisoft plateau boundaries.
- The findings contribute to the fundamental understanding of soft matter elasticity and material design.
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