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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
    Curvature elasticity and rotational viscosity of the nematic decylammonium chloride system (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5137-5142 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Experimental data are reported on curvature elasticity and rotational viscosity of micellar nematics formed in the decylammonium chloride/NH4Cl/H2O system. Two mixtures of different salt concentrations were studied (DACl:NH4Cl=10:1 and 20:1 by weight). The constants for the bend elasticity and the rotational viscosity were found to vary over nearly three orders of magnitude from 0.2×10−6 to 150×10−6 dyn and from 1 to about 1000 P, respectively. The large range is due to the divergence at the nematic–smectic transition. Both constants diverge with the same exponent. We obtained an exponent of 1.07±0.05 for a weight ratio DACl/NH4Cl of 20 and 0.87±0.02 for a ratio of 10, but an unexpected thermal hysteresis interfered with a reliable determination of the critical properties. Overall, the elastic properties and the divergence is this micellar nematic are similar to those observed in thermotropic nematics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454667
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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Critical properties of the uniaxial–biaxial transition in micellar nematic phases (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4046-4051 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The critical properties of the second order uniaxial–biaxial nematic transition (NL–Nbx) of the potassium laurate/1-decanol/D2O system were studied on surface and magnetic field aligned films of 0.1 and 0.5 mm thickness. The biaxial order was measured as a function of temperature and field. We find deviations from mean field behavior in a 20 mK range below the transition NL and in a temperature range of at least the same extent above the transition Nbx. The values obtained for the critical exponents of order parameter (β) and susceptibility (γ) in the uniaxial range are in good agreement with the values calculated for the xy model. A reliable value for the susceptibility exponent in the biaxial phase could not be obtained because the field range for which the effect is proportional to H2 is very small and the low field limit of the susceptibility could not be determined. From high field measurements we obtain a value of 4.0 as the lower limit for the exponent of the critical isotherm (δ). The result confirms that the transition follows the xy model. Drifts of the transition temperatures complicated the experiments. They are probably due to a partial esterification of potassium laurate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453858
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  • 7
    Electronic Resource
    Electronic Resource
    Liquid Crystals (1973)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physical Chemistry 24 (1973), S. 441-471 
    Details
    ISSN: 0066-426X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.pc.24.100173.002301
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  • 8
    Electronic Resource
    Electronic Resource
    Liquid crystalline phases of the sodium decylsulfate/decanol/water system. Nematic-nematic and cholesteric-cholesteric phase transitions (1980)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 102 (1980), S. 4879-4883 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00535a006
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic birefringence study of isotropic suspensions of tobacco mosaic virus (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 6740-6744 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The magnetic field induced birefringence in isotropic aqueous suspensions of tobacco mosaic virus (TMV) was measured as a function of temperature and concentration in high magnetic fields (100 kG). The temperature range was between 15 and 50 °C and the concentration range was between 4 and 20 mg/cm3. We find that the Cotton–Mouton constant (C) increases with decreasing temperature by 15%–20% over the entire range and extrapolates to infinity at a finite temperature of 110 to 150 K. At constant temperature, the measured ρ/C(ρ=number of TMV particles per cm3 of suspension) can be expanded in a power series of ρ, where the coefficients are expressed by the irreducible cluster integrals. At 20 °C the experimental values can be fitted to the linear form: ρ/λC=(2.09×1030–1.35×1015ρ)G2/cm3. For rigid cylindrical particles with l=3000 A(ring) and d=180 A(ring), and using the rigid hard particle interaction model, we find for the first order coefficient 0.62×1015, i.e., a significant deviation for the rigid hard-rod model. This deviation is also indicated by the variation of C with temperature. We discuss the results on TMV and of similar measurements on phage fd in terms of the interparticle interaction and rigidity of the particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453411
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of elastic constants and rotational viscosity of micellar liquid crystals by conductivity measurements (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 7372-7377 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An experimental study of a lyotropic nematic liquid crystal (CsPFO in a water solution) confined to a cylindrical tube is presented. The structure of the sample is controlled by a magnetic field. A small ac voltage is applied along the tube for conductivity measurements. Elastic constants and conductivity constants of the material are determined from static measurements at different magnetic fields. The method is also used to determine the rotational viscosity γ1 from dynamic response under sudden changes of the magnetic field. The dynamic measurements are analyzed in the framework of the Leslie–Ericksen theory. It is shown that although the dynamic behavior can be qualitatively explained with a single effective rotational viscosity γ1, back flow effects have to be taken into account should the analysis yield consistent values for γ1. The results obtained by this method agree well with other experimental studies. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473698
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