NMR spectra simulation of the magnetic reorientation of a lyotropic nematic polymer cell in the Freedericksz and a non-Freedericksz twist geometry

Casquilho, J. P.; Véron, A.; Martins, A. F.

doi:10.1088/0965-0393/14/2/012

Cited by 3 publications

(1 citation statement)

References 15 publications

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“…This out-of-plane component of the director may be homogeneous in space or periodic, in this case giving rise to a banded pattern. The analysis of these shearinduced instabilities, being a significant subject in the science of polymer liquid crystals (PLCs), has attracted considerable attention (2)(3)(4)(5)(6)(7)(8)(9)(10) and was modelled with the help of Rheo-Optics by Rey and co-workers (11,12) and of Rheo-RMN by Martins and co-workers (13,14). The suppression of these instabilities is a relevant subject for the processing of these materials and we investigate in this work the effect of an external magnetic field on the onset and growth conditions of the instabilities.…”

Section: Introductionmentioning

confidence: 99%

Perturbative analysis of the magnetic field effect on the stability of the shear flow of a nematic polymer

Figueirinhas

Casquilho

2008

Liquid Crystals

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The effect was investigated of an applied magnetic field on the stability of the shear flow of a nematic polymer liquid crystal of the tumbling type with respect to the formation of transient bands. For a given Ericksen number of the flow, the critical field that suppresses the thermally generated and shear amplified perturbations is calculated. The boundary in the control parameter space between the homogeneous and the band formation regime is calculated using a numerical simulation of the flow based on a time-dependent perturbative analysis. It is also found that the critical wavevector of the bands increases with the field and decreases with the Ericksen number of the flow and with the shear strain when a magnetic field is applied.

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Section: Introductionmentioning

confidence: 99%

Perturbative analysis of the magnetic field effect on the stability of the shear flow of a nematic polymer

Figueirinhas

Casquilho

2008

Liquid Crystals

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On the Effect of a Rotating Magnetic Field or Sample on the Bend Freedericksz Critical Field in Nematic Slabs

Guerra

Pinto

Martins

et al. 2009

Molecular Crystals and Liquid Crystals

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On the effect of an applied magnetic field on the shear-induced pattern formation in nematic polymer liquid crystals

Casquilho

2005

Eur. Phys. J. E

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The effect of an applied magnetic field and of the boundaries on the stability of the shear flow of nematic polymer liquid crystals of the tumbling type with respect to the formation of the transient spatially periodic patterns that appears after the start-up of shearing is studied. The unidirectional shear of a nematic director initially uniformly oriented orthogonally to the sample plane and with strong anchoring is considered. The magnetic field is applied orthogonally to the sample plane or in the same direction of the flow. For a given value of the Ericksen number of the flow a critical value of the magnetic-to-viscous energy ratio shows up above which the uniform flow is stable. When the influence of the boundaries may be neglected, an internal Ericksen number that stays constant in a given material is considered such that the wavelength of the periodic pattern is a self-adjusted length. An internal generalized Ericksen number is defined such that it is a universal function of the magnetic-to-viscous energy ratio.

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NMR spectra simulation of the magnetic reorientation of a lyotropic nematic polymer cell in the Freedericksz and a non-Freedericksz twist geometry

Cited by 3 publications

References 15 publications

Perturbative analysis of the magnetic field effect on the stability of the shear flow of a nematic polymer

Perturbative analysis of the magnetic field effect on the stability of the shear flow of a nematic polymer

On the Effect of a Rotating Magnetic Field or Sample on the Bend Freedericksz Critical Field in Nematic Slabs

On the effect of an applied magnetic field on the shear-induced pattern formation in nematic polymer liquid crystals

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