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Kent State University

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Full-Text Articles in Physics

Short-Range Smectic Order In Bent-Core Nematic Liquid Crystals, Seung Ho Hong, Rafael Verduzco, J. C. Williams, Robert J. Twieg, E. Dimasi, R. Pindak, Antal Jakli, Jim T. Gleeson, Samuel N. Sprunt Aug 2010

Short-Range Smectic Order In Bent-Core Nematic Liquid Crystals, Seung Ho Hong, Rafael Verduzco, J. C. Williams, Robert J. Twieg, E. Dimasi, R. Pindak, Antal Jakli, Jim T. Gleeson, Samuel N. Sprunt

Chemical Physics Publications

Small angle X-ray diffraction from the uniaxial nematic phase of certain bent-core liquid crystals is shown to be consistent with the presence of molecular clusters possessing short-range tilted smectic (smectic-C) order. Persistence of these clusters throughout the nematic phase, and even into the isotropic state, likely accounts for the unusual macroscopic behavior previously reported in bent-core nematics, including an anomalously large flexoelectric effect (similar to 1000 times that of conventional calamitic nematics), very large orientational and flow viscosities (similar to 10 100 and similar to 100 1000 times, respectively, typical values for calamitics), and an extraordinary flow birefringence observed in ...


Three-Dimensional Imaging Of Dielectric Patterns In Electrohydrodynamic Convection Of A Nematic Liquid Crystal, N. Gheorghiu, Ivan I. Smalyukh, Oleg Lavrentovich, Jim T. Gleeson Oct 2006

Three-Dimensional Imaging Of Dielectric Patterns In Electrohydrodynamic Convection Of A Nematic Liquid Crystal, N. Gheorghiu, Ivan I. Smalyukh, Oleg Lavrentovich, Jim T. Gleeson

Chemical Physics Publications

The transition from surface to bulk normal dielectric rolls in a nematic liquid crystal is imaged by fluorescence confocal polarizing microscopy. The three-dimensional director structure and the liquid flow are scanned in both the layer plane and the transverse plane. Two systems of small-scale convective flow are formed, one at each electrode. Strong anchoring makes director oscillations difficult and charges accumulate by the Carr-Helfrich mechanism. The middle region is a structureless convection where the director oscillates with the frequency of the applied voltage. The small-scale flow eventually fills the cell from one electrode to the other as one system of ...


Domain Size In The Presence Of Random Fields, E. Weinan, Peter Palffy-Muhoray Jan 1998

Domain Size In The Presence Of Random Fields, E. Weinan, Peter Palffy-Muhoray

Chemical Physics Publications

We consider the size of domains formed in ordered systems in the presence of quenched random fields. We argue that below the critical dimension, the, domain size shows a nonmonotonic dependence on the correlation length of the random field. If the random field is slowly varying in space, the order parameter follows the field, and the domain size is comparable to the correlation length. If the field is rapidly varying, the domain size becomes larger than the correlation length, and diverges as the correlation length of the random field goes to zero.


X-Ray Reflectivity Study Of Interface Roughness, Structure, And Morphology Of Alignment Layers And Thin Liquid-Crystal Films, Brian Cull, Yushan Shi, Satyendra Kumar Jan 1995

X-Ray Reflectivity Study Of Interface Roughness, Structure, And Morphology Of Alignment Layers And Thin Liquid-Crystal Films, Brian Cull, Yushan Shi, Satyendra Kumar

Physics Publications

We report results of x-ray reQectivity studies of thin conducting films, organic alignment layers, and liquid crystal films on Bat glass substrates. An understanding of these films is important for liquid crystal science and technology. Specular reflectivities of conducting layers of indium tin oxide, organic overlayers of lecithin, 12-8(poly)diacetylene polymerized with linearly polarized uv light, and spin-coated diheptylazoxy benzene films were measured. The evolution of surface roughness of soda-lime glass substrates as a function of chemical etching time was also studied. Using theoretical models based on the Fourier transform of electron density gradients and the matrix formalism of ...


Discotic Micellar Nematic And Lamellar Phases Under Shear-Flow, J. T. Mang, Satyendra Kumar, B. Hammouda Dec 1994

Discotic Micellar Nematic And Lamellar Phases Under Shear-Flow, J. T. Mang, Satyendra Kumar, B. Hammouda

Physics Publications

Small-angle neutron scattering was employed to study the effect of shear flow on the nematic (N) and lamellar (L(alpha)) phases in aqueous solutions of cesium perfluoro-octanoate. Shear rates as high as similar to 4000 s(-1) were used. The N phase was found to align with the director in the direction of the gradient velocity. The L, phase oriented with lamellae parallel to the shear plane. This change in equilibrium orientation is attributed, primarily, to changes in the value of the Ericksen viscosity parameter at. Subtle shear-rate-dependent director reorientations were also observed in the proximity of the N-to-L(alpha ...