The Homogeneous Alignment of Liquid Crystal Layers

Wolff, U.; Greubel, W.; Krüger, H. H.

doi:10.1080/15421407308083371

Cited by 75 publications

(25 citation statements)

References 3 publications

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“…The rubbing method involves rubbing the polymer-coated substrate surface against a cloth, and despite being a somewhat antiquated technique, the detailed mechanism of LC alignment by the rubbing process has yet to be reported. Recently, the alignment mechanism has been reported to be the result of geometric effects of structures such as grooves [1][2][3][4][5] or a uniaxis expanding effect of the polymer film [6][7][8][9][10]. Although uniform LC alignment can be readily achieved by the rubbing method, the method does present a number of problems, including the generation of dust and static electricity.…”

Section: Introductionmentioning

confidence: 99%

Relationship between surface order and surface azimuthal anchoring strength of nematic liquid crystals

et al. 2004

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The liquid-crystal molecular order near the rubbed polymer surface is reexamined by the improved torque balance method. The surface azimuthal anchoring strength measured by the improved torque balance method is several times larger than that believed conventionally, considered to be significantly affected by the phase-transition behavior. Based on this result, it can be argued that the correlation between the rubbing strength and the surface azimuthal anchoring strength should be improved in consideration of the mechanism of surface order.

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Section: Introductionmentioning

confidence: 99%

Relationship between surface order and surface azimuthal anchoring strength of nematic liquid crystals

et al. 2004

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“…The results described in this current study using polymer 1 , PMMA, and PVS suggest that this behavior also occurs in compressed Langmuir films of polymers with flexible backbones. We note here, however, that the alignment of LCs near surfaces and interfaces is sensitive to order and structure on a wide range of length scales (e.g., extending from oriented molecular chains to micrometer-scale topographical features) 1,2,56–58. In this context, it is possible that the films used in our current studies could have topographical features on the micrometer or nanometer length scale that could direct and account for the observed orientation of the LCs.…”

Section: Resultsmentioning

confidence: 80%

Langmuir films of flexible polymers transferred to aqueous/liquid crystal interfaces induce uniform azimuthal alignment of the liquid crystal

Kinsinger

Buck

Meli

et al. 2010

Journal of Colloid and Interface Science

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We reported recently that amphiphilic polymers can be assembled at interfaces created between aqueous phases and thermotropic liquid crystals (LCs) in ways that (i) couple the organization of the polymer to the order of the LC and (ii) respond to changes in the properties of aqueous phases that can be characterized as changes in the optical appearance of the LC. This investigation sought to characterize the behavior of aqueous-LC interfaces decorated with uniaxially compressed thin films of polymers transferred by Langmuir-Schaefer (LS) transfer. Here, we report physicochemical characterization of interfaces created between aqueous phases and the thermotropic LC 4-cyano-4'-pentylbiphenyl (5CB) decorated with Langmuir films of a novel amphiphilic polymer (polymer 1), synthesized by the addition of hydrophobic and hydrophilic side chains to poly(2-vinyl-4,4'-dimethylazlactone). Initial characterization of this system resulted in the unexpected observation of uniform azimuthal alignment of 5CB after LS transfer of the polymer films to aqueous-5CB interfaces. This paper describes characterization of Langmuir films of polymer 1 hosted at aqueous-5CB interfaces as well as the results of our investigations into the origins of the uniform ordering of the LC observed upon LS transfer. Our results, when combined, support the conclusion that uniform azimuthal alignment of 5CB is the result of long-range ordering of polymer chains in the Langmuir films (in a preferred direction orthogonal to the direction of compression) that is generated during uniaxial compression of the films prior to LS transfer. Although past studies of Langmuir films of polymers at aqueous-air interfaces have demonstrated that in-plane alignment of Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Supporting Information Available. Additional figures and other data showing: (i) surface pressure recorded during repeated compression and expansion of a Langmuir film of polymer 1, (ii) a fluorescent micrograph of a film of 5CB after Langmuir-Schafer transfer of polymer 1 TMR to the aqueous-5CB interface, (iii) a representative AFM image of a film of polymer 1 transferred to an OTScoated Si substrate, (iv) polarized light micrographs of a LC film after transfer of polymer 1 at an angle ~ 45° relative to the aqueous-air interface, (v) fractional transmittance of polarized light through polymer 1-laden LC interfaces transferred at various angles relative to the direction of compression, (vi) representative π-A isotherms of Langmuir films of PMMA and PVS, (vii) polarized FT-IR spectra of PMMA films on CaF 2 substra...

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“…One could see that for the NLC1 mixture system, due to the shorter alkyl carbon chain for NLC1, the contact area with the LC molecules was smaller, and the mutual interactions were lower. Therefore, from this result and Equation (5), one could infer that the anchoring energy for the VACOF was weaker.…”

Section: The Interaction Of Alkyl Acrylic Monomers With Different Carmentioning

confidence: 83%

Fabrication of pseudo-pi vertical alignment mode liquid crystal devices with ultra-violet polymerisation and investigations of their electro-optical characteristics

Ho¹,

Lee²

2010

Liquid Crystals

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In this study, we applied the non-contact photo-polymerisation method in fabricating pseudo-polyimide (PI) liquid crystal (LC) devices with vertical alignment copolymer films, in the hope of solving the problems associated with traditional rubbing alignment processes. We mixed different photo-polymerisation-type acrylic monomers and negative dielectric anisotropy LC at proper weight percentages, and induced phase separation behaviour between the photo-polymerisation-type acrylic monomers and the LC molecules in the LC mixture solution through ultraviolet light irradiation, thereby forming copolymer films with vertical alignment effects. We further conducted preliminary characterisation of the alignment mechanism, photo-polymerisation, etc., of the LC molecules and investigated their interactions with alkyl acrylic monomers with different carbon chain lengths (the analogue of alkyl side chains in traditionally used vertical alignment-type PI) and electro-optical properties such as the transmittance, contrast ratio, and response time.

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The Homogeneous Alignment of Liquid Crystal Layers

Cited by 75 publications

References 3 publications

Relationship between surface order and surface azimuthal anchoring strength of nematic liquid crystals

Relationship between surface order and surface azimuthal anchoring strength of nematic liquid crystals

Langmuir films of flexible polymers transferred to aqueous/liquid crystal interfaces induce uniform azimuthal alignment of the liquid crystal

Fabrication of pseudo-pi vertical alignment mode liquid crystal devices with ultra-violet polymerisation and investigations of their electro-optical characteristics

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