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Columnar Phases (columnar + phase)
Kinds of Columnar Phases Selected AbstractsSpontaneous Deracemization of Disc-like Molecules in the Columnar PhaseANGEWANDTE CHEMIE, Issue 2 2010Hiroki Nagayama Chirale Scheiben: Scheinbar flache scheibenförmige Moleküle bilden eine columnare Phase und trennen sich spontan in makroskopische chirale Domänen (Deracemisierung). Quantenchemische Rechnungen legen einen verdrillten axial-chiralen Kern dieser Moleküle nahe (siehe Bild). Das Zusammenlagern zu chiralen Überstrukturen wird in elektronischen und Schwingungs-Circulardichroismus-Spektren offensichtlich. [source] Mixed f-d Metallomesogens with an Extended Rigid CoreEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2005Koen Binnemans Abstract The liquid-crystalline behaviour of copper(II) and nickel(II) complexes of a mesogenic Schiff-base ligand derived from N,N' -disalicylidene-1,2-phenylenediamine (salophenH2) and of the corresponding trinuclear mixed copper(II)/lanthanum(III) and nickel(II)/lanthanum(III) complexes was investigated. High-temperature X-ray diffraction studies revealed that both the parent transition metal complexes and the mixed f-d complexes exhibit a hexagonal columnar phase (Colh) over an extended temperature range. Complex formation with lanthanum(III) nitrate resulted in an increase of the transition temperatures. The geometrical parameters (lattice parameters and column cross-section) of all the metal complexes are very similar, which indicates that the local organisation in the mesophase is the same despite their structural differences. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Planar Alignment of Columnar Discotic Liquid Crystals by Isotropic Phase Dewetting on Chemically Patterned SurfacesADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Jonathan P. Bramble Abstract A novel method of creating planar aligned columnar discotic liquid crystals (cDLCs) on surfaces, which also gives control over the azimuthal angle, is presented. Surfaces are chemically patterned with stripes via microcontact printing of organothiol self-assembled monolayers (SAMs) on gold, or via deep UV patterning of organosilane SAMs on silicon. These are then used to isolate long droplets of cDLCs by dewetting in the isotropic phase. Upon cooling from the isotropic into the hexagonal columnar phase, polarizing microscopy reveals that the cDLC aligns in a planar orientation. Results for three triphenylene derivatives (HAT-6, HHTT, H7T) and for a phthalocyanine derivative (8H2Pc) are presented. H7T and HAT-6 are found to align with the director perpendicular to the stripe direction, but HHTT and 8H2Pc align parallel to the stripe direction. This relatively simple new method for creating planar aligned columnar phases of DLCs gives control over the azimuthal angle: a condition required for organic field-effect transistor applications of cDLCs. [source] A Stimuli-Responsive, Photoluminescent, Anthracene-Based Liquid Crystal: Emission Color Determined by Thermal and Mechanical ProcessesADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Yoshimitsu Sagara Abstract Here, a photoluminescent liquid crystal that exhibits a change of emission color on the metastable,stable phase transition induced by external stimuli is prepared. A 2,6-diethynylanthracene derivative with amide groups and dendritic side chains exhibits a columnar phase on slow cooling from the isotropic phase and shows blue emission in this columnar phase. In contrast, a cubic phase is obtained by rapid cooling from the isotropic phase. In the cubic phase, the 2,6-diethynylanthracene cores form excimers, resulting in yellow emission. While the columnar phase is a stable liquid-crystalline (LC) phase, the cubic phase is a metastable LC phase. It is found that a change of the photoluminescent color from yellow to blue is observed on the cubic-columnar phase transition induced by heating or mechanical shearing for this 2,6-diethynylanthracene derivative in the cubic phase. This change of photoluminescent color is ascribed to the inhibition of excimer formation on the metastable,stable LC phase transition. [source] Macroscopically Aligned Ionic Self-Assembled Perylene-Surfactant Complexes within a Polymer Matrix,ADVANCED FUNCTIONAL MATERIALS, Issue 13 2008Ari Laiho Abstract Ionic self-assembled (ISA) surfactant complexes present a facile concept for self-assembly of various functional materials. However, no general scheme has been shown to allow their overall alignment beyond local polydomain-like order. Here we demonstrate that ionic complexes forming a columnar liquid-crystalline phase in bulk can be aligned within polymer blends upon shearing, taken that the matrix polymers have sufficiently high molecular weight. We use an ISA complex of N,N,-bis(ethylenetrimethylammonium)perylenediimide/bis(2-ethylhexyl) phosphate (Pery-BEHP) blended with different molecular weight polystyrenes (PS). Based on X-ray scattering studies and transmission electron microscopy the pure Pery-BEHP complex was found to form a two-dimensional oblique columnar phase where the perylene units stack within the columns. Blending the complex with PS lead to high aspect ratio Pery-BEHP aggregates with lateral dimension in the mesoscale, having internal columnar liquid-crystalline order similar to the pure Pery-BEHP complex. When the Pery-BEHP/PS blend was subjected to a shear flow field, the alignment of perylenes can be achieved but requires sufficiently high molecular weight of the polystyrene matrix. The concept also suggests a simple route for macroscopically aligned nanocomposites with conjugated columnar liquid-crystalline functional additives. [source] Distinct Columnar and Lamellar Liquid Crystalline Phases Formed by New Bolaamphiphiles with Linear and Branched Lateral Hydrocarbon ChainsCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2008Marko Prehm Dr. Abstract A universal building block for the convergent synthesis of a wide variety of different T-shaped ternary amphiphiles was developed and used for the synthesis of a series of new liquid-crystalline materials composed of a rigid biphenyl core with polar glycerol groups at both ends and linear or branched alkyl chains in a lateral position. In addition, compounds with bulky achiral (2,4,6-trimethylphenoxy, adamantane-1-carboxylate, benzoate) or chiral (menthyl or cholesteryl) substituents attached to the end of the lateral alkyl chain were also investigated. In all cases the lateral chains were connected to the aromatic core by an ether linkage. The effect of the ether linking unit on mesophase stability and mesophase type is discussed with respect to conformational effects. The liquid-crystalline phases were investigated by polarizing microscopy, calorimetry, and X-ray diffraction of surface aligned samples. Upon enlarging the lateral chains a series of different polygonal cylinder phases was observed, which were replaced by lamellar phases and a non-cylinder hexagonal columnar phase by further increasing the size of these substituents. Remarkably, only pentagonal, hexagonal, and giant hexagonal cylinder phases could be observed, whereas mesophases composed of cylinders with a smaller number of sides are missing. No distinct chirality effects were observed for the menthyl- and cholesteryl-substituted compounds. However, the rodlike shape of the polycyclic cholesteryl core leads to a unique phase structure combining an organization of the alicyclic cholesteryl cores perpendicular to the layer planes and the aromatic biphenyl cores parallel to the layer planes. [source] Columnar Mesomorphism in Hexacatenar Tetrahedral (2,2,-Bipyridine)zinc Complexes and Homologous Palladium DerivativesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2005Giovanna Barberio Abstract The synthesis and characterisation of novel liquid crystals which display columnar mesomorphism induced upon complexation of a series of nonmesomorphic hexacatenar 4,4,-disubstituted 2,2,-bipyridines (Ln) are reported. The introduction of different metal centres (Zn, Pd) causes the appearance of mesomorphism in all complexes regardless of the geometry around the metal ion. We therefore report the first examples of mesomorphism in tetrahedral zinc derivatives. The nature of the columnar phases is related to the self-assembly of the half-disc shaped [LnMCl2] (M = Zn, Pd) complexes into full disc-shaped supramolecules. The molecular organisation in the mesophase is mainly driven by intermolecular attractive interactions, as shown by the crystal structure of the model compound [LPdCl2]. Preliminary measurements of photoconductivity have been performed on samples of [LnMCl2] complexes doped with C60 to increase absorption. Promising results were obtained. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Planar Alignment of Columnar Discotic Liquid Crystals by Isotropic Phase Dewetting on Chemically Patterned SurfacesADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Jonathan P. Bramble Abstract A novel method of creating planar aligned columnar discotic liquid crystals (cDLCs) on surfaces, which also gives control over the azimuthal angle, is presented. Surfaces are chemically patterned with stripes via microcontact printing of organothiol self-assembled monolayers (SAMs) on gold, or via deep UV patterning of organosilane SAMs on silicon. These are then used to isolate long droplets of cDLCs by dewetting in the isotropic phase. Upon cooling from the isotropic into the hexagonal columnar phase, polarizing microscopy reveals that the cDLC aligns in a planar orientation. Results for three triphenylene derivatives (HAT-6, HHTT, H7T) and for a phthalocyanine derivative (8H2Pc) are presented. H7T and HAT-6 are found to align with the director perpendicular to the stripe direction, but HHTT and 8H2Pc align parallel to the stripe direction. This relatively simple new method for creating planar aligned columnar phases of DLCs gives control over the azimuthal angle: a condition required for organic field-effect transistor applications of cDLCs. [source] Synthesis and liquid crystalline properties of poly(1-alkyne)s carrying triphenylene discogensJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2008Changmin Xing Abstract Triphenylene-containing 1-decynes with different alkyl chain lengths and their polymers are synthesized and the effects of the structural variables on their mesomorphic properties are investigated. The monomers [HCC(CH2)8CO2C18H6 (OCmH2m+1)5; m = 4,9] are prepared by consecutive etherization, coupling, and esterification reactions. The monomers form columnar phases at room temperature. The polymerizations of the monomers are effected by [Rh(nbd)Cl]2, producing soluble polymers in high yields (up to 84%). The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, DSC, POM, and XRD analyses. All the polymers are thermally stable, losing little of their weights when heated to 300 °C. The isotropization temperature of the polymers increases initially with the length of alkyl chain but decreases on further extension. Although the polymers with shorter and longer alkyl chain lengths adopt a homogeneous hexagonal columnar structure, those with intermediate ones form mesophases with mixed structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2960,2974, 2008 [source] Columnar liquid-crystalline assemblies composed of spiropyran derivatives and sulfonic acids,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2008Boon-Hooi Tan Abstract A series of fan-shaped spiropyran derivatives with different length of alkyl chains has been synthesized. Liquid-crystalline (LC) assemblies of spiropyran derivatives have been formed by the addition of organic sulfonic acids such as trifluoromethylsulfonic acid, 10-camphorsulfonic acid, 4-methylbenzenesulfonic acid, and imidazolium-based ionic liquids (ILs) having a sulfonic acid group. Equimolar mixtures of a fan-shaped spiropyran derivative with the acidic imidazolium-based ILs exhibit columnar phases with wider LC temperature ranges as compared to those of other mixtures. The ionic interactions formed by the ionic imidazolium moieties should contribute to the stabilization of the columnar phases. On the other hand, equimolar mixtures of the spiropyran derivative with decane-1-sulfonic acid having a long alkyl chain and poly(4-styrenesulfonic acid) do not show mesomorphism. The chemical structure of organic sulfonic acids is a key factor for the induction and stabilization of the LC phases. Copyright © 2008 John Wiley & Sons, Ltd. [source] Star-Shaped Oligobenzoates: Non-conventional Mesogens Forming Columnar Helical MesophasesCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2008Matthias Lehmann Dr. Abstract Star-shaped mesogens with a phloroglucinol or a trimesic acid core and oligobenzoate arms with up to five repeating units have been synthesised. These non-conventional mesogens form various columnar mesophases over a broad temperature range. The liquid-crystal phases were characterised by optical microscopy, differential scanning calorimetry, X-ray diffraction, dilatometry and solid-state NMR spectroscopy. In addition to the high-temperature hexagonal columnar phases, the columnar self-assemblies undulate upon cooling and consequently form higher-ordered body-centred orthorhombic columnar 3D structures. A model of E -shaped folded conformers helically displaced along the columns is proposed. Helical preorganisation in the hexagonal phase precedes the transition to the low-temperature phases. Space filling and nano-segregation compete in the self-organisation process, thus aliphatic chains and the polar oligobenzoate scaffold are not perfectly separated in these star-shaped mesogens. [source] | |||||||||||||