The corkscrew instability of a Fréedericksz domain wall in a nematic liquid crystal

We report wormlike flexoelectric structures evolving deep in the Freedericksz state of a nematic layer of the liquid crystal cyanobiphenyl-(CH2)-cyanobiphenyl. They form in the predominantly splay-bend thin boundary layers and are built up of solitary flexoelectric domains of the Bobylev-Pikin type. Their formation is possibly triggered by the gradient flexoelectric surface instability that remains optically discernible up to unusually high frequencies. The threshold voltage at which the worms form scales as square root of the frequency; in their extended state, worms often appear as labyrinthine structures on a section of loops that separate regions of opposite director deviation. Such asymmetric loops are also derived through pincement-like dissociation of ring-shaped walls. Formation of isolated domains of bulk electroconvection precedes the onset of surface instabilities. In essence, far above the Freedericksz threshold, the twisted nematic layer behaves as a combination of two orthogonally oriented planar half-layers destabilized by localized flexoelectric distortion.

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Confined Electroconvective and Flexoelectric Instabilities Deep in the Freedericksz State of Nematic CB7CB

Krishnamurthy

Palakurthy

Yelamaggad

2017

J. Phys. Chem. B

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Planar-fingerprint transition in a thermoreversible liquid crystalline gel

et al. 2005

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A thermoreversible (physical) gel consisting of a nematic liquid crystal mixed with a small quantity of a chiral organogelator is investigated in the planar configuration. The response of the system to an external electric field reveals multistability within a small hysteresis. The relaxation of the liquid crystal under this field is characterized by two different time scales: a fast one that is connected to the tilt of the director field, and a slow one that describes the reorientation of the chiral structure. In the first case, the relaxation is nonexponential and can be described by a Kohlrausch-Williams-Watts law with a stretching parameter of 0.5.

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Transformation from walls to disclination lines: Statics and dynamics of the pincement transition

et al. 2005

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We present an experimental and theoretical study of the pincement phenomenon-transformation of a wall associated with the Fréedericksz transition into a pair of disclination lines. We measure the velocity of the boundary (front) between the two states as a function of the voltage. Experimental results are recovered by numerical simulations based on the nematic tensor order parameter, which also reveal the detailed three-dimensional structure of the front. By introducing reduced models we obtain approximate expressions for the two-state coexistence voltage and the front velocity. We find a bifurcation scenario incorporating a pair of saddle nodes at which the wall and disclination solutions appear or disappear.

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The corkscrew instability of a Fréedericksz domain wall in a nematic liquid crystal

Cited by 4 publications

References 27 publications

Confined Electroconvective and Flexoelectric Instabilities Deep in the Freedericksz State of Nematic CB7CB

Confined Electroconvective and Flexoelectric Instabilities Deep in the Freedericksz State of Nematic CB7CB

Planar-fingerprint transition in a thermoreversible liquid crystalline gel

Transformation from walls to disclination lines: Statics and dynamics of the pincement transition

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