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  • 1
    Electronic Resource
    Electronic Resource
    Effect of a polymer network on the alignment and the rotational viscosity of a nematic liquid crystal (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3161-3164 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polymer dispersions were made by photoinduced polymerization of 4,4'-bisacryloyl-biphenyl in liquid crystal 4-4'-cyano pentyl biphenyl as nematic solvent. Samples were prepared with 0.5, 1, and 1.5 wt % monomer. The polymerization was done in the isotropic phase. The rotational viscosities of the two lower concentration samples increased only moderately after UV curing (3 mW/cm2, 25 min). The 1.5 wt % sample gave under the same condition a nematic with a fairly rigid anisotropic network that did not realign in magnetic field up to 20 kG. We estimate that the mesh size of the network was in the order of 1 μm, significantly smaller than the magnetic coherence length of the solvent that is in the order of 5 μm. The diamagnetic anisotropies of the aligned samples were not affected significantly by the polymer. We studied electro-optical properties on thin films. The films were strongly light scattering but they could be switched to transparent state. We conclude that the polymer forms a network of loosely connected fibrils that interacts strongly with the director field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351478
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  • 2
    Electronic Resource
    Electronic Resource
    Helix deformation and bistable switching of ferroelectric liquid crystals (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1891-1894 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We studied electro-optical properties of 5–13-μm-thick films of a short pitch (0.43 μm) chiral smectic C liquid crystal in bookshelf structure. The anchoring at the silane treated surfaces was relatively weak so that the relaxed bookshelf structure was helical also at the surfaces. Low fields cause only a deformation of the helix. Larger fields unwind the helix and give a quasibistable switching since the helix recovers at zero fields only slowly via a nucleation process. There is an intermediate field range where the sample is in a mixed state: In some areas the helical structure remains stable, while in other areas switching occurs between two unwound states. In the intermediate field range bistable switching with a gray scale is possible. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361091
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  • 3
    Electronic Resource
    Electronic Resource
    Electrically induced uniform planar alignment of S*C liquid crystals on homeotropically treated plates (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2777-2779 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Chevron textures of SC* films are usually obtained with the conventional procedure where a planar alignment coating (e.g., buffed polyimide) is used. We describe a new technique which enables us to obtain uniform bookshelf textures which show bistability and can be switched with low fields (∼1 V/μm). This is achieved with a homeotropic surface coating. With a homeotropic coating the samples form a uniform texture with horizontal layers on cooling. The homeotropic texture becomes unstable under sufficiently strong electric fields and transforms to a birefringent texture with smectic layers oriented vertically. Without an additional bias the texture has domains of different layer orientations. By simultaneous application of a vertical field and horizontal shear stable uniform bookshelf textures can be obtained. Here we show that it is possible to obtain uniform bookshelf alignment by the simultaneous action of a horizontal field gradient and ac fields. The horizontal gradient leads to a more or less well-defined propagating front of the texture transformation. It results in a biased domain texture with vertical layers. The effect of the strong ac field (∼100 Hz) is to smooth out the domain texture. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112560
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  • 4
    Electronic Resource
    Electronic Resource
    Method to obtain uniform bookshelf textures in smectic C* liquid crystals (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2622-2624 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new method is described to obtain homogeneous bookshelf textures in thin films of ferroelectric smectic C* material with short pitch and high Ps. The surfaces were coated with silane to obtain a homeotropic texture. The sample was realigned to a homogeneous bookshelf texture under simultaneous application of an electric field and shearing. The texture is stable and gives a very good contrast (∼80) under permanent drive condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106900
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  • 5
    Electronic Resource
    Electronic Resource
    Electromechanical responses of antiferroelectric and ferrielectric liquid crystals (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 1101-1104 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We measured the electromechanical responses in the antiferroelectric and ferrielectric phases of the prototype antiferroelectric material (R)-MHPOBC. Our observations confirm recent results, which indicated that SmCβ* is ferrielectric, or at least not normal ferroelectric. In addition, we found that the layers become permanently tilted after dc field treatments. The mechanical responses are practically zero normal to the plates due to mechanical compensation of the electroclinic effect. This fact may have an importance in display applications, since a vertical vibration usually disturbs electro-optical performances. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369235
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  • 6
    Electronic Resource
    Electronic Resource
    Photodarkening and light induced anisotropy in chalcogenide glasses
    Amsterdam : Elsevier
    Solid State Communications 51 (1984), S. 761-764 
    Details
    ISSN: 0038-1098
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0038-1098(84)90461-7
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  • 7
    Electronic Resource
    Electronic Resource
    Memory of silica aggregates dispersed in smectic liquid crystals: Effect of the interface properties (1999)
    Springer
    The European physical journal 10 (1999), S. 509-513 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 61.30.-v Liquid crystals - 61.46.+w Clusters, nanoparticles, and nanocrystalline materials - 61.12.Ha Neutron reflectometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Previous studies on nematic liquid crystals containing silica particles indicated memory effects that might be due to hydrogen bonds between the individual silica particles. We made smectic liquid crystal dispersions containing silica particles with various surface properties. Using a neutron scattering technique we studied the interfacial surface effects on the structure of the silica aggregates, and on the smectic layer alignment. Our observations indicate that the stability of the memory correlates to the number of OH groups on the silica surfaces. The observations imply that, with fine-tuning of the OH content of the silica surfaces, various types of memory devices can be designed. We considered three different effects that can memorise the alignment of the liquid crystal. Measurements on tilted SmC phases indicate that surface effects become important only after repeated heating-cooling cycles, as the average size of the aggregates decrease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050880
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  • 8
    Electronic Resource
    Electronic Resource
    Tilted smectic layers of a liquid crystal between homeotropically treated plates (2000)
    Springer
    The European physical journal 1 (2000), S. 61-65 
    Details
    ISSN: 1292-895X
    Keywords: PACS. 61.30.-v Liquid crystals - 61.30.Cz Theory and models of liquid crystal structure - 61.30.Jf Defects in liquid crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We investigated SmC* films sandwiched between silane coated glass plates and observed formation of textures exhibiting a uniform tilt of the smectic layers with respect to the boundary plates. The layer tilt angle increases from zero to as the sample is cooled from the smectic A phase to room temperature. These films show linear electro-optical effects because the permanent polarization can be aligned so that it has a component parallel to the applied field without changing the layer structure. Our analysis indicates that mainly two effects determine the layer tilt. On the one hand, the surface tension tends to minimise the layer tilt. On the other hand, the surface energy promotes the director to be normal to the boundary plates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101890050007
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