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Articles 1 - 5 of 5
Full-Text Articles in Physical Sciences and Mathematics
Biaxial Nematic Order Induced By Smectic Fluctuations, C. Zhang, S. Chakraborty, T. Ostapenko, Samuel N. Sprunt, Antal Jakli, Jim T. Gleeson
Biaxial Nematic Order Induced By Smectic Fluctuations, C. Zhang, S. Chakraborty, T. Ostapenko, Samuel N. Sprunt, Antal Jakli, Jim T. Gleeson
Antal Jakli
We report on a series of measurements on the microscopic structure and the magneto-optical properties of a calamitic liquid crystalline compound in its nematic phase. Structural studies show the existence of short-range, tilted smectic order consistent with pretransitional effects above an underlying smectic phase. Concomitantly, magneto-optical results exhibit the existence of an optic axis not collinear with the uniaxial director. This apparent biaxial nature is discussed within the context of coupling between the tensor nematic and the smectic order parameters.
Optical Waveguiding In Bent-Core Liquid-Crystal Filaments, Jake Fontana, C. Bailey, Wolfgang Weissflog, I. Janossy, Antal Jakli
Optical Waveguiding In Bent-Core Liquid-Crystal Filaments, Jake Fontana, C. Bailey, Wolfgang Weissflog, I. Janossy, Antal Jakli
Antal Jakli
We demonstrate optical waveguiding in recently discovered free-standing bent-core liquid-crystal filaments. The bent-core liquid-crystal molecules in air self-assemble into a cylindrical geometry that is "solidlike" along the radial direction of the filament and liquid in the axial direction of the filament. These filaments are unique not only because they are fluids, but also because they are anisotropic. For this reason, their waveguiding properties not predictable need to be characterized. The light power transmitted through the filament was found to be independent of temperature from 180 degrees C to near room temperature. Initial defects of newly pulled filaments were found to …
Light-Induced Changes Of Optical And Electrical Properties In Bent-Core Azo Compounds, Antal Jakli, V. Prasad, D.S.S. Rao, Guangxun Liao, I. Janossy
Light-Induced Changes Of Optical And Electrical Properties In Bent-Core Azo Compounds, Antal Jakli, V. Prasad, D.S.S. Rao, Guangxun Liao, I. Janossy
Antal Jakli
We have studied the optical and electrical properties of two bent-core substances with an azo linkage in their cores. Pump-probe laser studies, direct textural observations, and spectrophotometric recordings show an initial decrease of light transmission, which at larger light intensities (similar to 1 mW/mm(2)) is followed by a bleaching. Simultaneously the electrical properties (electric conductivity, antiferroelectric polarization, switching threshold, and switching time) decreased monotonically with increasing light intensities. The monotonic decrease of electrical properties indicates that the darkening and bleaching have the same origin, namely, the photochemical isomerization of the azo linkage from the trans to the cis isomer. The …
Unexpected Liquid Crystalline Behaviour Of Three-Ring Bent-Core Mesogens: Bis(4-Subst.-Phenyl) 2-Methyl-Iso-Phthalates, Wolfgang Weissflog, Ute Baumeister, Maria-Gabriela Tamba, Gerhard Pelzl, Horst Kresse, Rudolf Friedemann, Gunther Hempel, Ricardo Kurz, Matthias Roos, Kurt Merzwiler, Antal Jakli, Cuiyu Zhang, Nicholas Diorio, Ralf Stannarius, Alexey Eremin, Ulrike Kornek
Unexpected Liquid Crystalline Behaviour Of Three-Ring Bent-Core Mesogens: Bis(4-Subst.-Phenyl) 2-Methyl-Iso-Phthalates, Wolfgang Weissflog, Ute Baumeister, Maria-Gabriela Tamba, Gerhard Pelzl, Horst Kresse, Rudolf Friedemann, Gunther Hempel, Ricardo Kurz, Matthias Roos, Kurt Merzwiler, Antal Jakli, Cuiyu Zhang, Nicholas Diorio, Ralf Stannarius, Alexey Eremin, Ulrike Kornek
Antal Jakli
Three-ring bent-core bis(4-subst.-phenyl) 2-methyl-iso-phthalates exhibiting nematic, SmA and SmC phases are reported. The occurring mesophases have been identified by their optical textures and X-ray diffraction measurements which give also geometrical structural parameters like layer spacing and molecular tilt. Quantum chemical calculations on single molecules and X-ray structure analysis in the crystalline state indicate wide opening angles (about 155 degrees) of the molecular legs due to the lateral methyl group in position 2 of the central phenyl ring. However solid state NMR spectroscopy in the liquid crystalline phases finds stronger molecular bending (bending angle to be about 138 degrees in the …
Ester Type Banana-Shaped Liquid Crystalline Monomers: Synthesis And Physical Properties, Katalin Fodor-Csorba, Aniko Vajda, Antal Jakli, Christian Slugovc, Gregor Trimmel, Dietrich Demus, Eszter Gacz-Baitz, Sandor Holly, Giancarlo Galli
Ester Type Banana-Shaped Liquid Crystalline Monomers: Synthesis And Physical Properties, Katalin Fodor-Csorba, Aniko Vajda, Antal Jakli, Christian Slugovc, Gregor Trimmel, Dietrich Demus, Eszter Gacz-Baitz, Sandor Holly, Giancarlo Galli
Antal Jakli
New ester-type banana (bent-shaped) monomers, 1,3-phenylene bis[4'-(alken-1-yloxy)-biphenyl-4-carboxylate] s Ia - Vb, with different substituent(s) on the central phenyl ring (H, CH3, Cl or NO2) and alkenyl tails in the side arms ( decenyl or undecenyl) were prepared. The analogues IIIa - IVb with 4-chloro- or 4,6-dichloro-substituents exhibited a nematic phase, while Va, Vb with 2-nitro-substituent showed a B-7 phase at relatively low temperature. All the compounds were stable, no degradation or polymerization was observed under applied electric fields or heat treatments. Electro-hydrodynamic instabilities were observed in the nematic phase of each sample. In the B-7 phase of Vb there was …