Columnar Discotic Liquid Crystals Research Articles

Thermotropic Liquid Crystals Based on Chito-Oligosaccharides. 1. Synthesis of Chitobiose Octaalkanoates and Chitotriose Undecaalkanoates and Their Thermal Properties

Abstract This paper deals with the preparation of two series of chito-oligosaccharide derivatives, chitobiose octaalkanoates, and chitotriose undecaalkanoates, in which the amino- and hydroxyl groups were blocked with alkyl pendants of differing lengths via an ester linkage. By differential scanning calorimetry(DSC) and optical microscopic observations, these compounds were found to exhibit an enantiotropic mesophase at temperatures ranging from ca. 50 °C to ca. 200 °C. The texture of the mesophases were similar to those of the discotic columnar liquid crystals formed by the cellobiose and cellotriose equivalents. However, the amido group in the chito-derivatives seems to stabilize the mesophase to an appreciable extent, bringing about higher temperatures and a longer temperature span of the mesophase than those of the cello-equivalents.

Rayleigh scattering from column undulations in a discotic liquid crystal.

Depolarized Rayleigh scattering on a columnar discotic liquid crystal is described. Column undulations and mode quantization allows the scattering to be visible only for two directions of reciprocal space, and for well-defined light propagation angles. The observed constant angular extension of the scattering shows that column undulations are not controlled by curvature elasticity, but by an anisotropic 3D solidlike elasticity. This behavior is probably associated with column entanglement, as recently discussed by Prost.

Discotic Liquid Crystals of Transition Metal Complexes 111: The First π-Acceptor in Discotic Columnar Liquid Crystals Obtained from Octasubstituted Bis(diphenylethane-1,2-dithiolene)nickel Complexes

Abstract Disk-like complexes, bis[l,2-di(3′,4′-di-n-alkylphenyl)ethane-l,2-dithiolene]nickel (n-alkyl = n-hexyl, n-octyl) and bis[1,2-di(3′,4′-di-n-decyloxyphenyl)ethane-1,2-dithiolene]nickel have been synthesized and characterized. It was found that n-decyloxy derivative exhibits a hexagonal disordered columnar (Dhd) mesophase while n-alkyl derivatives are not discotic liquid crystals but isotropic liquids at room temperature. The half-wave potentials for reduction of these complexes is -0.04 ∼ -0.06V. n-Decyloxy derivative is the first π-acceptor in discotic columnar liquid crystals.

Discotic Liquid Crystals of Transition Metal Complexes 131: Synthesis and Discotic Columnar Mesomorphism of π-Donor Bis[1,2-di(3′,4′-di-n-alkoxyphenyl)ethane-1,2-dioximato]nickel(II) Complexes

Abstract Disk-like complexes, bis[1,2-di(3′,4′-di-n-alkoxyphenyl)ethane-1,2-dioximato]nickel(II) (abbreviated as [(CnO)4DPG]2Ni, n = 4, 8, 12) have been synthesized and characterized. The [(CnO)4DPG]2Ni (n = 4, 8, 12) complexes exhibit discotic hexagonal disordered columnar (Dhd) mesophases. Interestingly, it was found that the [(C8O)4DPG]2Ni complex has two kinds of Dhd mesophases. These complexes are the first discotic columnar liquid crystals in the bis(glyoximato)metal(II) system.

Discotic Liquid Crystals of Transition Metal Complexes 121: The Effect of the Alkoxy Chain Length on the Mesomorphism of Bis[1,2-di(3′,4′-di-n-alkoxyphenyl)ethane-1,2-dithiolene]nickel Complexes

Abstract A series of disk-like complexes, bis[1,2-di(3′,4′-di-n-alkoxyphenyl)ethane-1,2-dithiolene]nickel (abbreviated as [(CnO)4DPD]2Ni, n = 1 ∼ 12) have been synthesized in focusing our interest on the effect of the alkoxy chain length on the discotic mesomorphism. It was found that the [(CnO)4DPD]2Ni (n = 2 ∼ 4) complexes have a monotropic discophase, and that the [(CnO)4DPD]2Ni (n = 5 ∼ 12) complexes have an enantiotropic discophase (Dhd). The half-wave potentials for reduction of the [(CnO)4DPD]2Ni (n = 1 ∼ 12) complexes are -0.05 ∼ -0.06V (vs. SCE in dichloromethane solution). It is noteworthy that the π-acceptor discotic columnar liquid crystals can be obtained without impairment of the π-acceptor ability by introduction of the long alkoxy chains to the bis(dithiolene)nickel complex.

ChemInform Abstract: Liquid‐Crystalline Compounds. Part 43. Hexaalkylnylbenzene Derivatives, the First Hydrocarbons as New Columnar or Nematic Discotic Liquid Crystals.

AbstractPd(II)‐catalyzed coupling of hexabromobenzene (I) with the terminal alkynes (II) yields the hexaalkynylbenzenes (III).

Phase Transitions in Discotic Liquid Crystals

AbstractThe phase diagram of a columnar discotic liquid crystal is evaluated within a Landau theory and the results are compared with the data obtained from 13C NMR measurements on hexapentoxy‐triphenylene.