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  • 1
    Electronic Resource
    Electronic Resource
    A method for the determination of the elastic constant ratio K33/K11 in nematic liquid crystals (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7280-7287 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed analysis of the recently proposed [Appl. Phys. Lett. 60, 3226 (1992)] method for the direct determination of the bend-to-splay bulk elastic constant ratio (K33/K11) in nematic liquid crystals is presented. K33/K11 is directly measured from the optical birefringence pattern of an escaped-radial nematic director field using the Frank elastic free-energy approach to determine the stable structure in supramicrometer capillary tubes with strong homeotropic anchoring conditions. No external field or a priori knowledge of the anisotropy in magnetic or electric susceptibility is required. The simple experimental setup used is available in most laboratories, making this an attractive and convenient technique to probe the elastic character of nematic materials. The results for 5CB and PCH-5 are in good agreement with data obtained from conventional electo-optic and magneto-optic techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354017
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  • 2
    Electronic Resource
    Electronic Resource
    Nematic director orientation in a liquid-crystal-dispersed polymer: A deuterium nuclear-magnetic-resonance approach (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 135-143 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nuclear-magnetic-resonance (NMR) technique is employed to liquid-crystal-dispersed-polymer (LCDP) systems. Deuterium NMR is used to determine director distributions in LCDP cells in the presence of a magnetic field. The samples consist of a nematic liquid crystal mixed with small percentages of a monomer that is polymerized under different conditions after dissolving it in the liquid crystal. NMR spectra of the deuterated liquid-crystal molecules give information on orientation and order in such systems. The orientation of the polymer skeleton formed during the polymerization is found to be stable. It determines the orientation of the nematic director even in the presence of a strong external magnetic field. Simple models for the director field are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350326
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of the cylindrical cavities of Anopore and Nuclepore membranes (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 7788-7796 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microscopic properties of the inner surface of the cavities of Anopore and Nuclepore membranes are investigated with scanning electron microscopy (SEM), nitrogen adsorption isotherms, and deuterium nuclear magnetic resonance (2H-NMR). Useful information about the cavity orientation and morphology, and internal surface area is obtained. Analysis of SEM photographs yields estimates of the surface area and the porosity of these membranes which complements the adsorption results. The orientation of liquid crystals permeated in the cavities of Anopore and Nuclepore membranes is probed with the 2H-NMR technique. It is found that the orientation of the liquid crystal molecules is governed by the confining volume and surface conditions. The 2H-NMR spectral line shape of the confined liquid crystal also provides information on the substrate morphology and roughness that is consistent with SEM and adsorption experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462376
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  • 4
    Electronic Resource
    Electronic Resource
    Deuteron spin relaxation and molecular dynamics of a nematic liquid crystal (5CB) in cylindrical microcavities (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 3540-3547 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Spin–lattice and spin–spin relaxation times of deuterium nuclei have been measured for a nematic liquid crystal confined in cylindrical channels of diameter 0.2 μm. In the isotropic phase the relaxation in the MHz regime is not affected by the confinement. The possibility of rotating the cylinders with respect to the magnetic field enables the first direct measurements of the anisotropy of deuteron relaxation of a monomeric liquid crystal in the nematic phase. The observed temperature dependence of the spin–spin relaxation rate in the isotropic phase roughly obeys the (T−T*)−1 law and allows the determination of the average time the molecules reside at the wall, which is 5×10−5 s for 5CB at the lecithin coated surfaces. In the nematic phase the spin–spin relaxation rate is affected by order director fluctuations and rotation induced by translational diffusion at orientations with a nonhomogeneous director distribution with respect to the magnetic field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464074
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  • 5
    Electronic Resource
    Electronic Resource
    Nematic director-fields captured in polymer networks confined to spherical droplets (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1968-1971 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The director-field of a nematic liquid crystal droplet is captured by a polymer network. The anisotropic polymer network is formed by photopolymerizing a small amount of monomer (2 wt %) in a nematic solvent suspended in a glycerin matrix. The glycerin matrix enforces parallel surface anchoring and a lecithin dopant is used to promote homeotropic surface anchoring. Polymer networks formed under these surface conditions as well as under applied electric fields are characterized with optical polarizing microscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356319
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  • 6
    Electronic Resource
    Electronic Resource
    K33/K11 determination in nematic liquid crystals: An optical birefringence technique (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 3226-3228 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical birefringence patterns of nematic liquid crystals constrained to supramicrometer capillary tubes with homeotropic anchoring are sensitive to the detailed bulk elastic properties of the nematic material. The bend-to-splay elastic constant ratio (K33/K11) is estimated by comparing the escaped-radial nematic director field observed via optical polarizing microscopy to simulated textures predicted by the Frank elastic theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106701
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of the electric field on the quasibookshelf stripe deformation in an electroclinic liquid crystal (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2937-2939 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quantitative study of the effect of electric field on the stripe domains formed by layer deformation in chiral smectic A liquid crystals is presented. X-ray diffraction studies reveal that the angle between the layer normals in adjacent stripe domains increases with increasing electric field. A simple model is presented to derive the true molecular tilt angle from optical transmission measurements. The relationship between the optical tilt angle and the tilt angle evaluated from x-ray measurements of the smectic layer thickness indicates that the molecules are tilting as rigid rods. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112540
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  • 8
    Electronic Resource
    Electronic Resource
    Expanded viewing-angle reflection from diffuse holographic-polymer dispersed liquid crystal films (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 4262-4264 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A switchable diffuse reflective film with high color purity is demonstrated using holographic-polymer dispersed liquid crystals (HPDLC). By recording a diffuse hologram directly into the LC/polymer film, the diffuse mode HPDLC exhibit viewing angles an order of magnitude larger than the conventional mode. A simple phenomenological model based on coupled-wave theory is developed to describe our observations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1335544
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  • 9
    Electronic Resource
    Electronic Resource
    Diffusion kinetics of formation of holographic polymer-dispersed liquid crystal display materials (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2235-2237 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The underlying physical phenomena behind the increased reflection/diffraction efficiency of holographically formed polymer-dispersed liquid crystal gratings formed from blended oligomers are investigated. Using parameters determined by in situ diffraction measurements during grating formation, a phenomenological diffusion model shows that a composition modulation in the polymer network results in blended oligomer systems. Scanning electron microscope studies reveal polymer morphologies consistent with this hypothesis. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126306
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  • 10
    Electronic Resource
    Electronic Resource
    Formation dynamics of diffraction gratings in reactive liquid crystals (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 296-298 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using in situ diffraction measurements of diffraction grating formation in a single component reactive mesogen system, the anisotropy in the diffusion constants is determined. The data are well explained by a diffusion model, which accounts for the density modulation due to shrinkage upon photopolymerization with interfering laser beams. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1385343
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