Structural and dielectric investigations of a binary system of a bi-swallow-tailed and a terminally-polar compound

Induced smectic A phases in binary mixtures of a bi-swallow-tailed component and a second component are described as 'filled smectic A phases', since the second rod-like component is considered to occupy spaces between the terminal branches of the bi-swallow-tailed molecules. A new system of this kind is now described where the second rod-like component has a terminal dipole, thereby enabling dielectric studies of the mixtures. These measurements coupled with calorimetric and X-ray measurements give information about the packing and dynamics of the mixed phases.     

Solidification-induced and shear-induced band texture in thermotropic liquid crystalline polymer films

Two phase diagrams of a six-ring double-swallow-tailed compound are presented where the mixing components involve electron-acceptor compounds. In the mixed phase region, nematic, smectic A and C, cubic and columnar phases are induced. In this way transitions between lamellar, cubic and columnar phases can be realized by variation of the con- centration. The mesophases occurring in these systems have been characterized by X-ray investigations.     

Structures, properties and miscibility behaviour of liquid crystalline polycatenar tetrone derivatives

The tetrones represent an interesting new mesogenic building block. The results of this study show that they can be incorporated into a variety of mesophases. A smectic phase was observed in the polycatenar compound with four terminal chains as expected. The phase exhibits a tilted structure (S_c phase) to prevent void formation. The compound with six pendant chains forms a columnar phase. In spite of their structural similarity, the tetrones studied tended not to be completely miscible. However, complete miscibility with a semi-discoid phenylhydrazone was observed. When this hydrazone, which forms a columnar 'D_ho phase', was mixed with tetrone which forms a columnar 'D_hd phase' a columnar hexagonal phase was produced with enhanced stability. We believe that the stability enhancement derives from a charge transfer interaction between the tetrone and the phenylhydrazone.     

13C-NMR-spektroskopische untersuchung der tricarbonyl(1,2,3,4,5,2′-η-ethylcyclopentadien-1,2′-diyl)- komplexe des molybdäns und wolframs. deformierte σ-alkyl-π-cyclopentadienyl-metall-komplexe

Reactions of dialkylzinc compounds ZnR₂ (R  Me, Et) with pyrogallol (PG) have been carried out.The reaction products obtained with mole ratios of reactants 3/1 2/1 and 1/1, respectively, were characterized by means of IR, ¹H NMR spectroscopy, elemental analysis and cryometry.The product formed from ZnR₂/PG 2/1 (the best known catalytic system for the alternating CO₂/propylene oxide copolymerization) was found to be 1,3,2-benzodioxazincol-4-alkylzincolate.     

Sulphur ligated siamese twin mesogens

The synthesis of 3,3'-sulphinyl-bis-[alkyl 4-(4-substituted benzoyloxy)-benzoates] and 3,3'-sulphonyl-bis-[alkyl 4-(4-substituent-benzoyloxy)-benzoates] is described. These new nematic compounds are of the ligated siamese twin type. By microscopy and DSC calorimetry the thermal behaviour was investigated. Many of the new compounds transform on quenching to the glassy nematic state with glass temperatures above room temperature. Above the glass temperature the substances behave like highly viscous but ordinary nematics. The substances may be used for the construction of new thermo-electrooptic displays. By means of dielectric and X-ray investigations we were able to show that the two halves of the twin molecules are in an antiparallel orientation in the nematic state. In mixtures of the new compounds with rod-like nematics reentrant nematic behaviour was observed.     

Strukturbildung von homologen wasserfreien Lecithinen in Abhängigkeit von Temperatur und Kristallisationsbedingungen

The influence of temperature and crystallization of homologous lecithins on the phase transition was studied by X-ray diffraction. The different conditions of crystallization effect various structures. The structural differences between various samples of dimyristoyl-phosphatidyl-choline, di-palmitoyl-phosphatidyl-choline and di-stearoyl-phosphatidyl-choline were discussed and their lattice parameters compared. The results show that the polymorphism of the lecithins are depended on the chain length and the conditions of crystallization.     

On the molecular and mesophase structures of disc-like tetrapalladium liquid crystals

Abstract

Various members of two series of μ-halogeno-bridged tetrapalladium mesogens each with twelve dodecyloxy chains, but differing in the size of their large disc-like macroheterocyclic cores, 1 a-e and 2a-c, as well as one new short-chained homologue (1 c') of one of the series, as a model compound for single crystal X-ray studies, are presented. Our results on that model compound again unambiguously confirm earlier statements about the unique molecular structure of the core of these flat tetrapalladium complexes. The properties of all thermomesogenic compounds have been studied by differential scanning calorimetry, polarizing microscopy, and also by X-ray diffraction; the latter method reveals an oblique arrangement of disordered columns in most of the mesophases exhibited by the members of both series 1 and 2.     

Chiral ordering in the nematic and an optically isotropic mesophase of bent-core mesogens with a halogen substituent at the central core

Two new homologous series of bent-core compounds have been synthesized. Their mesophase behaviour has been investigated by polarizing microscopy, differential scanning calorimetry, X-ray diffraction, NMR spectroscopy, and by dielectric and electro-optical measurements. It was found that, with one exception, all the chlorine-substituted compounds form a nematic phase and an optically isotropic ‘banana phase’. The latter phase shows spontaneously chiral domains of opposite handedness. This phase may be considered as a type of smectic blue phase. The mesophase behaviour of the homologous bromine-substituted compounds is more complicated. Depending on the chain length, B₆, columnar, nematic or the isotropic ‘banana phase’ occur.