Elliptical diffusion of dye in hexagonal columnar polycatenar mesophases

We have studied polycatenar compounds which exhibit hexagonal columnar mesophases. In the planar orientation of these mesophases, the elliptical diffusion of the dissolved dyes is visualized by taking several pictures of the sample. The diffusion ratio D// /D is deduced for these columnar mesophases. Furthermore, using a classical optical absorption technique, we present measurements of dye diffusion in the same mesophases. The diffusion constants are measured in two geometries, along and perpendicular to the columns. The diffusion anisotropy ratios are in agreement with those deduced from the ellipse axes. The structure of these new columnar mesophases exhibited by rod-like mesogens is compared with that of disk-like mesogens.     

Elliptical diffusion of dye in hexagonal columnar polycatenar mesophases

We have studied polycatenar compounds which exhibit hexagonal columnar mesophases. In the planar orientation of these mesophases, the elliptical diffusion of the dissolved dyes is visualized by taking several pictures of the sample. The diffusion ratio D// /D is deduced for these columnar mesophases. Furthermore, using a classical optical absorption technique, we present measurements of dye diffusion in the same mesophases. The diffusion constants are measured in two geometries, along and perpendicular to the columns. The diffusion anisotropy ratios are in agreement with those deduced from the ellipse axes. The structure of these new columnar mesophases exhibited by rod-like mesogens is compared with that of disk-like mesogens.     

Tetrabenzocyclododecatetraene A new core for mesogens exhibiting columnar mesophases

Octasubstituted derivatives of tetrabenzocyclododecatetraene are found to exhibit thermotropic mesophases. The molecules of these mesogens are highly flexible with an average four-fold symmetry. Optical and differential scanning calorimetry measurements are presented on five ester and ether derivatives. All mesophases appear to be columnar with a negative optical anisotropy. From the five compounds studied the four which are derived from aliphatic ester and ether are optically uniaxial, while the mesophase of the decylbenzoyloxy derivative could be biaxial. Miscibility measurements performed with some discotic and pyramidic mesogens of similar molecular dimensions suggest that the mesophases of the tetrabenzocyclododecatetraene core form new families of columnar mesophases.     

Tetrabenzocyclododecatetraene A new core for mesogens exhibiting columnar mesophases

Abstract

Octasubstituted derivatives of tetrabenzocyclododecatetraene are found to exhibit thermotropic mesophases. The molecules of these mesogens are highly flexible with an average four-fold symmetry. Optical and differential scanning calorimetry measurements are presented on five ester and ether derivatives. All mesophases appear to be columnar with a negative optical anisotropy. From the five compounds studied the four which are derived from aliphatic ester and ether are optically uniaxial, while the mesophase of the decylbenzoyloxy derivative could be biaxial. Miscibility measurements performed with some discotic and pyramidic mesogens of similar molecular dimensions suggest that the mesophases of the tetrabenzocyclododecatetraene core form new families of columnar mesophases.     

Kojic acid—a new fragment for the preparation of bent-core mesogens

Kojic acid was used to synthesize bent-core mesogens. Antiferroelectric polar smectic mesophases, an oblique and a rectangular columnar mesophase were found. The mesophases were characterized by X-ray scattering, electro-optical measurements, polarizing microscopy and DSC. On the base of these measurements, models of the mesophases are proposed.     

Kojic acid—a new fragment for the preparation of bent‐core mesogens

Kojic acid was used to synthesize bent‐core mesogens. Antiferroelectric polar smectic mesophases, an oblique and a rectangular columnar mesophase were found. The mesophases were characterized by X‐ray scattering, electro‐optical measurements, polarizing microscopy and DSC. On the base of these measurements, models of the mesophases are proposed.     

Lyotropic liquid-crystalline mesophases and a novel, solid physical form of some water-soluble, reactive dyes

A novel, solid physical form has been observed when some water-soluble, reactive dyes are isolated from aqueous solution, as sodium salts, by the addition of sodium chloride. This quasi-crystalline form has a fibrous morphology, is birefringent but is not crystalline. Dyes of this type are known to form lyotropic liquid-crystalline mesophases in water. Preliminary X-ray diffraction investigations, reported here, for the mesophases formed by two such dyes indicate that they have columnar structures of the type first proposed for the lyotropic mesophases of the disodium chromglycate/water system and subsequently for other drug and dye molecules. X-ray and electron diffraction studies of the quasi-crystalline form show that it has a closely related columnar structure. The quasi-crystalline form is postulated to result from the formation and subsequent precipitation of columnar dye aggregates, as sodium chloride is added to the aqueous dye solution.     

Columnar liquid crystalline pi-conjugated oligothiophenes

Polycatenar oligothiophenes possessing three alkoxy chains at each terminal self-organise into columnar liquid crystalline phases, and one-dimensional columnar stacks can be oriented uniaxially by mechanical shearing in the mesophases.     

Structural studies of columnar phases of some chiral disc-like molecules

We have performed a structural study of the mesophases of some isomeric hexa-substituted phenanthrenes. Evidence for a new hexagonal columnar mesophase with three columns per unit cell was found in a chiral isomer. Moreover, a rectangular columnar phase with four columns per lattice, similar to the low temperature mesophase of a hexa-substituted rufigallol, was found in a different material. The relations between the structures and the electro-optical behaviour of the different mesophases are discussed.     

Molecular structure and mesomorphism in the series of discotic esters derived from benzene,triazine, biphenyl,and triphenylene

New mesogenic discotic triazine-based esters were synthesized and shown to form a low-temperature monotropic columnar mesophase. Using as examples the newly synthesized compounds and previously prepared discotic esters on the basis of benzene, biphenyl, and triphenylene, the effects of the nature and size of the central fragment and the number, position, length, and rigidity of peripheral substituents therein on the mesomorphic properties (in particular, the ability to form columnar and nematic mesophases) were examined. The main structural factors stabilizing columnar and nematic mesophases were revealed. Nematic mesomorphism was shown to be favored by increased size of the central fragment of the discogen molecule and by the presence of cyclohexane fragments in peripheral substituents.     

Lyotropic liquid-crystalline mesophases and a novel,solid physical form of some water-soluble,reactive dyes

Abstract

A novel, solid physical form has been observed when some water-soluble, reactive dyes are isolated from aqueous solution, as sodium salts, by the addition of sodium chloride. This quasi-crystalline form has a fibrous morphology, is birefringent but is not crystalline. Dyes of this type are known to form lyotropic liquid-crystalline mesophases in water. Preliminary X-ray diffraction investigations, reported here, for the mesophases formed by two such dyes indicate that they have columnar structures of the type first proposed for the lyotropic mesophases of the disodium chromglycate/water system and subsequently for other drug and dye molecules. X-ray and electron diffraction studies of the quasi-crystalline form show that it has a closely related columnar structure. The quasi-crystalline form is postulated to result from the formation and subsequent precipitation of columnar dye aggregates, as sodium chloride is added to the aqueous dye solution.     

Self-assembled discotic liquid crystals formed by hydrogen bonding of alkoxystilbazoles

A series of discotic liquid crystals formed by simple hydrogen bonding between phloroglucinol core and alkoxystilbazole peripheral units was prepared. Nematic columnar and hexagonal columnar mesophases were observed depending on the length of alkyl chains around the aromatic core.     

Phase behaviour of star-shaped binary mixtures of triphenylbenzenes,triphenylboroxines and triphenyltriazines

ABSTRACT

Star-shaped nonaalkoxy-1,3,5-triphenyltriazines were prepared and their mesomorphism was investigated by differential scanning calorimetry (DSC), polarised optical microscopy (POM) and X-ray diffraction (WAXS and SAXS). Compounds with chain lengths C₉ – C₁₂ displayed enantiotropic hexagonal columnar mesophases over a wide range of temperature. Their similarity in molecular size and mesomorphism prompted us to study their binary mixtures with previously reported planar 1,3,5-triphenylboroxines and propeller-shaped 1,3,5-triphenylbenzenes. All three compounds are fully miscible in their hexagonal columnar mesophases, but mixtures of planar with propeller-shaped compounds generated columnar stacks that contain only one type of molecule to avoid their shape incompatibility. However, the two types of columnar stacks were fully miscible which circumvented macroscopic phase separation.     

Liquid crystalline salen manganese(III) complexes. Mesomorphic and catalytic behaviour

Several salen manganese(III) complexes displaying stable columnar mesophases in a wide range of temperatures have been synthesized. In condensed phases the molecules are assembled into dimers through intermolecular manganese-oxygen interactions and the columnar structure of the mesophases consist of the stacking of supramolecular discs formed by the association of two or three dimers, depending on the number and location of alkoxy chains in the complex. The catalytic activity of the complexes in solution has been studied, and they behave as efficient homogeneous catalysts in the epoxidation of styrene with iodosylbenzene as oxidant.     

Bis(salicylaldiminate) copper(II) and palladium(II) complexes: towards columnar mesophases

Copper and palladium complexes of new salicylaldimines derived from 3,4,5-tridecyloxyaniline, 2,3,4-tridecyloxyaniline and 4-decyloxyaniline have been synthesized and characterized. All the ligands bear four or more aliphatic chains with the aim of inducing columnar mesophases at low temperatures. In particular, metal complexes derived from 4-(3,4,5-tridecyloxybenzoyloxy)-salicyliden-3,4,5-tridecyloxyaninile display rectangular columnar mesophases at (or near) room temperature. These mesophase assignments have been confirmed by X-ray diffraction. A significant decrease of the melting points of the compounds is observed in the tridecyloxyaniline derivatives compared with those of similar complexes derived from mono- or di-decyloxyaniline.     

Toward well-organised ionic discotic liquid crystals via versatile supramolecular approach

Various ordered structures of crystalline three-dimensional (3D) cubic, 2D columnar or 1D lamellar mesophases have been facilely achieved through host–guest interactions of electrically neutral host tris(18-crown-6)triphenylene and guest potassium sulfonates with alkyl tails of variant number and length. The convenient construction of functionalised ionic complexes and the flexibility of such a supramolecular approach offer a wide variety of possibilities to prepare various ordered functional soft materials, especially those in their 2D ordered columnar liquid crystalline mesophases may serve as promising electron and ion dual-channel transport organic electronic materials.     

2D and 3D ordered columnar liquid crystal phases by bundles of bolaamphiphiles with swallow-tail side chains

Two new mesophases, a longitudinally correlated and a noncorrelated (columnar) hexagonal phase, were obtained for a polyphilic bolaamphiphile with laterally attached swallow-tail chains; the unique feature of these mesophases, which makes them distinct from previously reported LC phases, is the organization of rod-like units in bundles parallel to the column axis.     

Columnar liquid crystals derived from ester-substituted tetraphenylenes

We report the synthesis and liquid crystalline properties of novel ester-substituted tetraphenylenes obtained from octamethoxytetraphenylene by demethylation and esterification. The target compounds display focal-conic textures typical for columnar mesophases, which are either rectangular or hexagonal columnar in nature, depending on the alkyl chain length.     

Bis(salicylaldiminate) copper(II) and palladium(II) complexes: towards columnar mesophases

Copper and palladium complexes of new salicylaldimines derived from 3,4,5-tridecyloxyaniline, 2,3,4-tridecyloxyaniline and 4-decyloxyaniline have been synthesized and characterized. All the ligands bear four or more aliphatic chains with the aim of inducing columnar mesophases at low temperatures. In particular, metal complexes derived from 4-(3,4,5-tridecyloxybenzoyloxy)-salicyliden-3,4,5-tridecyloxyaninile display rectangular columnar mesophases at (or near) room temperature. These mesophase assignments have been confirmed by X-ray diffraction. A significant decrease of the melting points of the compounds is observed in the tridecyloxyaniline derivatives compared with those of similar complexes derived from mono- or di-decyloxyaniline.     

A study of the self-assembly of 2-deoxyguanosine 3 5-cyclic monophosphate, d(cGp), by CD and X-ray diffraction

2-Deoxyguanosine 3 5-cyclic monophosphate forms in water cholesteric and hexagonal columnar mesophases. The polymorphic behaviour and the structural building blocks of the liquid crystalline phases, as determined by optical microscopy, CD spectroscopy and X-ray diffraction, are comparable to those found with all the deoxyguanylates investigated so far (in particular with deoxuguanosine 5- and 3-monophosphate). The present results show that the formation of a stacked array of planar G-tetramers, a necessary condition for the existence of the columnar mesophases, occurs even in the absence of hydrogen bonding groups linking the molecules along the length of the columns.