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Full-Text Articles in Physics
Capillary Filling Of Nematic Liquid Crystals, Xiang-Dong Mi, Deng-Ke Yang
Capillary Filling Of Nematic Liquid Crystals, Xiang-Dong Mi, Deng-Ke Yang
Deng-Ke Yang
We studied the orientation of nematic liquid crystals when they were being filled into cells by capillary action. We found that, in the flow front, the liquid crystal was always aligned along the flow direction. Far behind the flow front, the orientation of the liquid crystal depended on the anchoring direction of the alignment layers and the direction and speed of the flow. In cells with the anchoring direction parallel to the flow direction, the liquid crystal always oriented along the flow direction. In cells with the anchoring direction perpendicular to the flow direction, at low flow speed gradients, the …
Ordering And Self-Diffusion In The 1st Molecular Layer At A Liquid-Crystal Polymer Interface, G. P. Crawford, Deng-Ke Yang, S. Zumer, D. Finotello, J. William Doane
Ordering And Self-Diffusion In The 1st Molecular Layer At A Liquid-Crystal Polymer Interface, G. P. Crawford, Deng-Ke Yang, S. Zumer, D. Finotello, J. William Doane
Deng-Ke Yang
H-2 NMR of a liquid crystal confined to submicron cylindrical cavities, in a 17-K interval above the nematic-isotropic transition, reveals a weakly orientationally ordered molecular layer at the cavity wall governed by local interactions. The order (S0 = 0.02) is temperature independent so that a partial wetting is realized with no prewetting transition expected. A molecular exchange rate between the surface layer and the bulk is measured to be approximately 10(3) s-1. The coherence length measuring the order penetrating further into the cavity is described by alpha = 0.4 and xi-0 = 0.6 nm.
Evolution Of Disclinations In Cholesteric Liquid Crystals, F. Zhang, Deng-Ke Yang
Evolution Of Disclinations In Cholesteric Liquid Crystals, F. Zhang, Deng-Ke Yang
Deng-Ke Yang
We studied the evolution of defect lines (oily streaks) in cholesteric liquid crystals. In contrast to nematic liquid crystals, there were no interactions between the defect lines in cholesteric liquid crystals. We observed experimentally that individual open defect segments shrank with time with a linear relation, and individual defect loops shrank with time with a square root relation. We also observed that the defects in cholesteric liquid crystals were mainly interconnected loops, and the total length of the defect lines decreased with time logarithmically because of the distribution of loop size. The decay constant depended on the helical pitch of …
Pretransitional Nematic Ordering In Liquid Crystals With Dispersed Polymer Networks, Y. K. Fung, A. Borstnik, S. Zumer, Deng-Ke Yang, J. William Doane
Pretransitional Nematic Ordering In Liquid Crystals With Dispersed Polymer Networks, Y. K. Fung, A. Borstnik, S. Zumer, Deng-Ke Yang, J. William Doane
Deng-Ke Yang
The birefringence induced by partially ordered polymer networks dispersed in an isotropic phase of liquid crystals is studied. Polymer networks were formed by the polymerization of 1-4 % mixtures of prepolymer in the nematic phase of liquid crystals. The partial nematic (paranematic) ordering is analyzed in terms of the Landau-de Gennes approach using a simple model of an array of thin fibrils, which can, on a large scale, form bundles of polymer-rich material. The comparison of the theory and birefringence data clearly shows that the main building bloc of the network is a few nanometers thick fibril. The average thickness …
Effect Of Chiral Dopant On The Performance Of Polymer Dispersed Liquid Crystal Light Valve, Z. J. Lu, Deng-Ke Yang
Effect Of Chiral Dopant On The Performance Of Polymer Dispersed Liquid Crystal Light Valve, Z. J. Lu, Deng-Ke Yang
Deng-Ke Yang
We have experimentally studied the effect of chiraldopant on the electro‐optical performance of a polymer‐dispersed liquid crystal(PDLC) light valve. Adding a small amount of chiraldopant decreases the turn‐OFF time significantly but increases the drive voltage only slightly. A phenomenological theory is presented to explain the experimental results.