Director Reorientation in a Cell with Time-Dependent Anchoring Due To Adsorption/Desorption of LC Molecules

Romanenko, Alexander; Pinkevich, I. P.; Reshetnyak, Victor; Dozov, I.; Stoenescu, D

doi:10.1080/15421400490502517

Cited by 9 publications

(6 citation statements)

References 7 publications

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“…It should be noted that both models are described by the same equations (see Ref. 22), and the difference is just in the physical meaning of these equations. Thus, to settle between these two alternative mechanisms is a rather difficult task.…”

Section: Zenithal Anchoring Of Lc On Pvcn-f Films and The Drift Of Thmentioning

confidence: 99%

Anchoring and gliding of easy axis of 5CB on photoaligning PVCN‐F surface

Buluy¹,

Iljin²,

Ouskova³

et al. 2006

J Soc Info Display

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International audienceAbstract— The photoaligning properties of the popular photoaligning material polyvinyl-4(fluorocinnamate) (PVCN-F) are presented. The aligning quality and azimuthal and zenithal anchoring energy were measured and the drift of the easy orientation axis (gliding effect) on the PVCN-F surface, depending on UV exposure, was studied. Special attention is paid to unraveling the contribution of the adsorption liquid-crystal molecules onto the aligning surface to the anchoring properties of PVCNF and measuring the drift of the easy orientation axis over the PVCN-F surface. It is shown that a relatively weak azimuthal anchoring energy (Waz ∼ 10−7 − 10−5 J/m2) leads to strong drift of the easy axis in the azimuthal plane that was observed in a moderate (∼0.1–0.3 T) magnetic field. A much stronger polar anchoring (Wzen ∼ 10−4 J/m2) allowed us to observe the essential gliding of the easy axis in the zenithal plane in a rather strong electric field (∼5 V/μm)

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Section: Zenithal Anchoring Of Lc On Pvcn-f Films and The Drift Of Thmentioning

confidence: 99%

Anchoring and gliding of easy axis of 5CB on photoaligning PVCN‐F surface

Buluy¹,

Iljin²,

Ouskova³

et al. 2006

J Soc Info Display

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“…The gliding of the easy axis is usually explained in terms of an anisotropic adsorptiondesorption of nematic molecules at the interfaces [12,14,15] although, in the case of polymeric substrates, a reorientation of polymeric segments could also play some role [13]. This regime is very general and has always been observed in both weak and moderately strong anchoring substrates.…”

Section: Introductionmentioning

confidence: 97%

“…According to the proposed models of gliding [13,15,18] and to some experimental results with weak anchoring [4], one expects that the easy axis tends to align along the electric field, which initially forms angle b585u with respect to the initial orientation of the easy axis. Then, Dw Ã s t ð Þ~DQ s t ð Þ{DQ s n:e: ð Þ tends to A o 5b2DQ s (n.e.…”

mentioning

confidence: 99%

Azimuthal director gliding at a strongly anchoring interface of polyimide

Faetti

Marianelli

2006

Liquid Crystals

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A gliding of the director at the interface between a nematic liquid crystal and a solid medium is generally observed at many interfaces giving weak or moderately strong anchoring. This phenomenon is characterized by strongly non-linear dynamics and very long relaxation times (hours-days). The gliding of the director has also been observed very recently at the interface between a rubbed polyimide layer and a nematic liquid crystal which gives strong azimuthal anchoring. However, due to the weak nature of the experimental signals that characterizes the strong anchoring, this latter measurement was appreciably affected by thermal drift. In this paper, we develop a new experimental reflectometric method whereby the thermal drift is appreciably reduced. The method allows us to obtain more accurate signals and to investigate their time dependence. It is shown that the director gliding is well represented by a stretched exponential, as well as in the case of weak anchoring substrates. These measurements confirm that the gliding of the director is a universal phenomenon characterizing any kind of substrate with either weak and strong anchoring

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“…Since we found experimentally that the initial alignment of the LC in the cell is given by the reference substrate, we assumed that the angular distribution of the adsorbed LC molecules is determined mostly by the average azimuthal orientation of the LC in the bulk. In this case, the distribution function g(φ,ϕ(t)) of the adsorbed LC molecules is the projection of the bulk LC molecules' distribution onto the surface [32,33]. This can be written as…”

Section: Additional Experiments and Discussionmentioning

confidence: 99%

Photoinduced anchoring on a chalcogenide surface

et al. 2012

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We present basic characteristics and a model of photoinduced anchoring of liquid crystals (LCs) on a chalcogenide surface. It was found that characteristics of the alignment strongly depend on the LC material for the same chalcogenide glass. The photoalignment is partially reversible and can be controlled by changing the light polarization direction. We propose a model in which the existence of dichroic units on the chalcogenide surface and competition between two mechanisms of the photoalignment is suggested. The first mechanism is related to the light-induced anisotropy on the chalcogenide surface and results in an easy orientation axes of a LC parallel to the polarization of the incident light. The second mechanism is attributed to an energy transfer from the dichroic units after the light absorption to the LC molecules adsorbed on the chalcogenide surface. The transferred energy causes polarization-sensitive desorption of the LC molecules from the chalcogenide surface and the light-induced easy orientation axis of a LC perpendicular to the incident light polarization. The competition between these mechanisms leads to the observed change of the direction of the easy axis with the exposure.

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Director Reorientation in a Cell with Time-Dependent Anchoring Due To Adsorption/Desorption of LC Molecules

Cited by 9 publications

References 7 publications

Anchoring and gliding of easy axis of 5CB on photoaligning PVCN‐F surface

Anchoring and gliding of easy axis of 5CB on photoaligning PVCN‐F surface

Azimuthal director gliding at a strongly anchoring interface of polyimide

Photoinduced anchoring on a chalcogenide surface

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