Electromechanical effects in cholesteric and chiral smectic liquid‐crystalline elastomers

Brand, Helmut R.

doi:10.1002/marc.1989.030100902

Cited by 73 publications

(42 citation statements)

References 16 publications

(1 reference statement)

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“…The coupling ∼ D 2 between strains and relative rotations has no analogue for any other known optically isotropic system. The contribution ∼ ζ R can be viewed as the analogue of rotato-electricity as studied before for cholesteric elastomers and gels [48,49,60]. What is worth emphasizing about the effect given here is the fact that it gives rise to an effect linear in an external electric field in an optically isotropic system (before the field is applied).…”

Section: The Macroscopic Dynamics Of the Elastic Chiral εT Phasementioning

confidence: 85%

“…While relative rotations between octupolar order and a (transient or permanent) network have not been considered before, the concept of relative rotations goes back to nematic gels and has been pioneered by de Gennes [46]. Subsequently it has been applied to uniaxial magnetic gels [47] as well as to cholesteric gels and elastomers [38,48,49].…”

Section: The Macroscopic Dynamics Of the Elastic εT D Phasementioning

confidence: 99%

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On the influence of a network on optically isotropic fluid phases with tetrahedral/octupolar order

Brand

Pleiner

2017

Eur. Phys. J. E

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Abstract.We investigate the influence of transient or permanent elasticity on liquid phases with octupolar (tetrahedral) order, a question that has never been addressed before. The focus will be on optically isotropic liquid phases with tetrahedral order including the T d phase and the chiral T phase introduced by Fel. It turns out that the presence of both, a network as well as tetrahedral order can lead to the formation of chiral domains of both hands in an optically isotropic fluid due to a completely novel mechanism, thus providing a possible macroscopic explanation for recent experimental observations. We study in detail how elasticity influences the macroscopic dynamics of both, the T d and the T phase. The simultaneous presence of a transient network as well as of octupolar order is shown to lead to completely new crosscoupling phenomena for optically isotropic systems including transient dissipative elastic strains due to temperature gradients.

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Section: The Macroscopic Dynamics Of the Elastic Chiral εT Phasementioning

confidence: 85%

Section: The Macroscopic Dynamics Of the Elastic εT D Phasementioning

confidence: 99%

On the influence of a network on optically isotropic fluid phases with tetrahedral/octupolar order

Brand

Pleiner

2017

Eur. Phys. J. E

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“…and describe electric field-induced relative rotations (rotato-electricity [61,62]) and deformations with…”

Section: Macroscopic Dynamics Of Chiral Polar Gelsmentioning

confidence: 99%

Macroscopic behavior of polar nematic gels and elastomers

2016

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Abstract. We present the derivation of the macroscopic equations for uniaxial polar nematic gels and elastomers. We include the strain field as well as relative rotations as independent dynamic macroscopic degrees of freedom. As a consequence, special emphasis is laid on possible static and dynamic cross-couplings between these macroscopic degrees of freedom associated with the network, and the other macroscopic degrees of freedom including reorientations of the macroscopic polarization. In particular, we find static and dissipative dynamic cross-couplings between strain fields and relative rotations on one hand and the macroscopic polarization on the other that allow for new possibilities to manipulate polar nematics. To give one example each for the effects of a static and a dissipative cross-coupling: we find that a static electric field applied perpendicularly to the polar preferred direction leads to relative rotations while dynamically relative rotations can lead to transverse electric currents. In addition to a permanent network, we also consider the effect of a transient network, which is particularly important for the case of gels, melts and concentrated polymer solutions. A section on the influence of macroscopic chirality is included as well.

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“…Several authors have used a phenomenological approach to study strain-induced polarization in nematic elastomers (Terentjev 1993) and cholesteric elastomers (Brand 1989;Pelcovits & Meyer 1995). This work differs from all the above in that it describes strain using the full (nonlinear) deformation gradient tensor, and works directly with the polarization pseudovector rather than the free energy.…”

Section: Phenomenological Approachmentioning

confidence: 99%

Strain-induced polarization in non-ideal chiral nematic elastomers

Biggins

2009

Proc. R. Soc. A.

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Symmetry arguments are advanced that, although ideal chiral nematic elastomers cannot show strain-induced electrical polarization, non-ideal ones can. Phenomenological arguments are then presented, which predict a simple and universal form for the direction and strain dependence of the polarization. A microscopic minimal model is also developed, which predicts the same form. Finally, an example of a polarization-strain curve is calculated for a typical experimental geometry. In this geometry, the polarization is exactly zero at both small and large strains, but pronounced for a large set of intermediate strains corresponding to the strains that cause incremental rotation of the nematic director.

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Electromechanical effects in cholesteric and chiral smectic liquid‐crystalline elastomers

Cited by 73 publications

References 16 publications

On the influence of a network on optically isotropic fluid phases with tetrahedral/octupolar order

On the influence of a network on optically isotropic fluid phases with tetrahedral/octupolar order

Macroscopic behavior of polar nematic gels and elastomers

Strain-induced polarization in non-ideal chiral nematic elastomers

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