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Unwinding of a strained cholesteric elastomer by disclination loop nucleation
A C Callan-Jones1, Robert A Pelcovits, Robert B Meyer
1Department of Physics, Brown University, Providence, Rhode Island 02912, USA.
Summary
Applying strain to cholesteric elastomers unwinds their helix. Including Frank elasticity reduces the required strain and makes the cholesteric state metastable, enabling texture removal via disclination loops.
Area of Science:
- Materials Science
- Polymer Physics
- Soft Matter Physics
Background:
- Monodomain cholesteric elastomers exhibit a helical structure.
- Previous theories on helix unwinding under strain overlooked Frank elasticity.
- Understanding strain-induced transitions is crucial for elastomer applications.
Purpose of the Study:
- To investigate the effect of Frank elasticity on the strain-induced unwinding of cholesteric elastomer helices.
- To analyze the metastability of the cholesteric state above the transition.
- To study the mechanism of helical texture removal via disclination loop nucleation.
Main Methods:
- Theoretical analysis incorporating Frank elasticity.
- Approximate calculation of nucleation barrier energy.
- Finite-element modeling of elastomer behavior.
Main Results:
- Frank elasticity reduces the strain required to unwind the cholesteric helix.
- The cholesteric state becomes metastable above the unwinding transition.
- Nucleation of twist disclination loops provides a mechanism for texture removal in the metastable state.
Conclusions:
- Frank elasticity plays a significant role in the mechanical response of cholesteric elastomers.
- The metastability and subsequent texture removal mechanism are critical for understanding elastomer behavior under strain.
- Finite-element modeling offers a more accurate approach to studying these complex phenomena.
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