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Articles 1 - 4 of 4
Full-Text Articles in Physics
A Comparison Of Short-Range Molecular Order In Bent-Core And Rod-Like Nematic Liquid Crystals, S. Chakraborty, J. T. Gleeson, Antal Jákli, Samuel Sprunt
A Comparison Of Short-Range Molecular Order In Bent-Core And Rod-Like Nematic Liquid Crystals, S. Chakraborty, J. T. Gleeson, Antal Jákli, Samuel Sprunt
Antal Jakli
Thermotropic liquid crystals exhibit strongly temperature-dependent positional correlations among molecules in the nematic phase above the transition to a smectic-A or C phase. However, even in the absence of a lower temperature smectic phase, nematics composed of reduced symmetry molecules (bent-core mesogens, for example) reveal small angle X-ray scattering (SAXS) patterns with features similar to those associated with pretransitional smectic order. We report on a quantitative analysis and comparison of two-dimensional SAXS data on a bent-core nematic compound (lacking a smectic phase) and a rod-like nematic (exhibiting a nematic to smectic-C transition). This analysis demonstrates that a nanostructure based on …
Polar Bent-Shape Liquid Crystals - From Molecular Bend To Layer Splay And Chirality, Antal Jakli, A. Eremin
Polar Bent-Shape Liquid Crystals - From Molecular Bend To Layer Splay And Chirality, Antal Jakli, A. Eremin
Antal Jakli
Considerable progress has been achieved in understanding the fascinating structure and physical properties of the ferroelectric liquid crystalline phases formed by bent-core liquid crystals (BLC). In this review, we discuss a manifold of polar structures and phases found in BLCs such as orthogonal and tilted ferro-/antiferroelectric phases, smectic phases, switchable columnar phases, modulated structures and phases stabilised by a periodic lattice of defects such as dark conglomerate and nanofilament phases. We review the theoretical aspects of ferroelectricity in BLCs including existing microscopic theories and computer simulations, polarity and chirality phenomena. The last part of the paper is devoted to the …
Search For Biaxiality In A Shape-Persistent Bent-Core Nematic Liquid Crystal, Young-Ki Kim, Madhabi Majumdar, Bohdan I. Senyuk, Luana Tortora, Jens Seltmann, Matthias Lehmann, Antal Jakli, Jim T. Gleeson, Oleg Lavrentovich, Samuel Sprunt
Search For Biaxiality In A Shape-Persistent Bent-Core Nematic Liquid Crystal, Young-Ki Kim, Madhabi Majumdar, Bohdan I. Senyuk, Luana Tortora, Jens Seltmann, Matthias Lehmann, Antal Jakli, Jim T. Gleeson, Oleg Lavrentovich, Samuel Sprunt
Antal Jakli
Using a range of optical techniques, we have probed the nature of orientational order in a thermotropic bent-core liquid crystal, which features a shape-persistent molecular architecture designed to promote a biaxial nematic phase. In the upper range of the nematic phase (enantiotropic regime), dynamic light scattering reveals strong fluctuations attributable to the biaxial order parameter, in addition to the usual uniaxial director modes. Assuming a Landau-type expansion of the orientational free energy, we estimate the correlation length associated with these fluctuations to be similar to 100 nm. At lower temperatures, and mainly in the monotropic regime of the nematic, we …
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 …