Experimental study of the director pattern dynamics in the vicinity of the Fréedericksz twist geometry

Gonçalves, L. N.; Casquilho, J. P.; Ribeiro, A. C.

doi:10.1080/02678290310001605901

Cited by 2 publications

(2 citation statements)

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“…[10] Nematic liquid crystals are viscoelastic textured diamagnetic materials. For rod-like mesogens, the diamagnetic susceptibility w a is positive and the impositions of a sufficiently strong magnetic field M creates alignment along the field, a phenomenon known as the Fredericsz transition; [13,14] for a uniformly aligned director field, the magnetic field induced transition occurs at a critical value M c and is second order while for non-uniform director field, the re-orientation starts at infinitesimal fields. [14] Figure 1 (left) shows a disk embedded in a nematic liquid crystal matrix, where due to strong homeotropic anchoring the director is distorted by a splay deformations and where a pair of disclination defect lines nucleate close to the interface.…”

Section: Introductionmentioning

confidence: 99%

“…ð13Þ Equation (13) shows that under strong anchoring the magnetic force causes shape distortions and director distortions. This paper uses thermally induced phase separation-phase ordering-texturing in flexible polymernematic liquid crystal blends in the presence of magnetic field with the objective of manipulating droplet (disks in 2D) shapes in the resulting morphologies.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic Field‐Induced Shape Transitions in Multiphase Polymer‐Liquid Crystal Blends

Das

Rey

2006

Macro Theory & Simulations

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Summary: This paper presents a computational study of phase separation-phase ordering-texturing in blends of polymer coils and rod-like nematic liquid crystals under the presence of magnetic fields, using an extended version of the MatsuyamaEvans-Cates model (Phys. Rev. E 2000, 61, 2977. This work demonstrates that demixing in these blends leads to droplet morphologies with tunable droplet shapes and director textures. In contrast to filled nematics, where solids are suspended in a nematic liquid crystal matrix, demixing in coil-mesogenic rods blends leads to nematic emulsions, in which the deformable viscoelastic polymer drops are suspended in a nematic matrix. Under strong anchoring conditions, the imposition of a magnetic field leads to a director re-orientation that due to strong anchoring produces a droplet shape change. Magnetic field-induced shape transitions in these blends are shown to be second order with a finite critical field threshold that diverges as anchoring strength vanishes. A morphologicaltexture diagram summarizes the magnetic field-anchoring conditions that promote anisotropic shapes. This work presents additional material processing routes to design and control biphasic morphologies in polymer-liquid crystal blend.Computed morphology phase diagram in terms of magnetic field strength L M and anchoring strength. L fQ .

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