Showing papers on "Lyotropic liquid crystal published in 2001"
TL;DR: The use of the cross-linked inverted hexagonal phase in templated nanocomposite formation and heterogeneous catalysis has been demonstrated and the polymerization of LLC mesogens in the regular hexagonal and bicontinuous cubic phases is being targeted for future developments in functional materials.
Abstract: The development of functional materials with nanometer-scale architectures and the effect of these architectures on their chemical and physical properties are currently of great interest in materials design Polymerizable lyotropic liquid crystal (LLC) assemblies provide a facile entry into this area by allowing one to fix the inherent order in these systems using covalent bonds to create robust, nanostructured materials The use of the cross-linked inverted hexagonal phase in templated nanocomposite formation and heterogeneous catalysis has been demonstrated Additionally, the polymerization of LLC mesogens in the regular hexagonal and bicontinuous cubic phases is being targeted for future developments in functional materials Future directions for new applications of these materials are also discussed
219 citations
TL;DR: In this article, the interactions of poly(ethylene oxide) with cosolvents and surfactants with block copolymers (Poloxamers) are addressed. And the effects that the different cosolsvents or surfactant exhibit on the Poloxamer phase behavior are interpreted in terms of the preference of the cosolvent/surfactant molecules to locate in different domains of the PEO-PPO-PEO block copolerant self-assembly.
119 citations
TL;DR: In vitro antimycotic inhibitory activity of 1% itraconazole from liquid crystal, was conducted using agar-cup method and Candida albicans as a test organism and Fourier transform infrared spectroscopy revealed that there was no complex or any interaction between the surfactant and the drug.
113 citations
TL;DR: In this article, a hexagonal array of cylindrical pores was used to produce nanostructured cobalt films on gold substrates by electrochemical deposition of cobalt from cobalt acetate dissolved in the aqueous domains of the hexagonal Lyotropic liquid crystalline phase of Brij 56(C16EO10).
Abstract: Lyotropic liquid crystalline phases formed at high concentrations of nonionic surfactants provide a versatile templating medium that can be used to produce nanostructured materials with regular arrays of pores of nanometer dimension and extended periodicity. In this work, we have used this technique to prepare nanostructured cobalt films on gold substrates by electrochemical deposition of cobalt from cobalt acetate dissolved in the aqueous domains of the hexagonal lyotropic liquid crystalline phase of Brij 56(C16EO10). Low angle X-ray and transmission electron microscope studies show that the resulting cobalt films have a regular nanostructure consisting of a hexagonal array of cylindrical pores. The repeat distance for this nanostructure lies in the range of 7-11 nm and can be systematically varied by varying the amount of n-heptane added to the template mixture. Preliminary magnetic measurements on the nanostructured samples suggest that the coercivity (H-c) of these cobalt films is three to five times greater than that for polycrystalline cobalt and that it varies systematically with the size of the pores.
96 citations
TL;DR: A new stress versus shear rate diagram is built up that includes temporal behavior of lyotropic lamellar phase under shear flow and sustained oscillations of the viscosity correspond to periodic structural change of the entire sample between a disordered and an ordered state of multilamellar vesicles.
Abstract: We report some time-dependent behavior of lyotropic lamellar phase under shear flow. At fixed stress, near a layering instability, the system presents an oscillating shear rate. We build up a new stress versus shear rate diagram that includes temporal behavior. This diagram is made of two distinct branches of stationary states which correspond, respectively, to disordered and ordered multilamellar vesicle phases. When increasing the shear stress, prior to the transition to the ordered structural state, sustained oscillations of the viscosity are recorded. They correspond to periodic structural change of the entire sample between a disordered and a ordered state of multilamellar vesicles.
92 citations
TL;DR: In this article, the first large mesopore organosilicas were obtained using bridged silsesquioxane (RO)3SiCH2CH2Si(OR)3 precursors and triblock copolymers in acid media.
90 citations
TL;DR: In this article, the phase morphologies of amphiphilic poly(butadiene-b-ethylene oxide) (PB−PEO) block copolymers are studied using transmission electron microscopy, small-angle X-ray scattering, smallangle neutron scattering, and polarized optical microscopy.
Abstract: Lyotropic phase morphologies of amphiphilic poly(butadiene-b-ethylene oxide) (PB−PEO) block copolymers are studied using transmission electron microscopy, small-angle X-ray scattering, small-angle neutron scattering, and polarized optical microscopy. The PB−PEO block copolymers form type-1 lyotropic phases comprising disordered micellar solutions (L1), spheres arranged on a bcc lattice (I1), hexagonally packed cylinders (H1), and lamellae (Lα). Increasing molecular weight destabilizes the I1 and H1 phases and lowers the degree of order. For high molecular weight block copolymers the increase in chain conformational entropy leads to the formation of the sponge phase (L3). The transmission electron micrographs allow a detailed analysis of packing defects and epitaxial relations of the block copolymer lyotropic phases.
84 citations
TL;DR: A hypothesis that accounts for the cosolvent effects on the self-assembly of PEO-PPO-PEO block copolymers and can be used to predict them is developed.
74 citations
TL;DR: In this article, the authors describe the polymerization and segregation behavior of polar and non-polar monomers in an LLC environment, and the fastest polymerization for these monomers are observed in the highly ordered lamellar mesophase with the minimum polymerization rate observed in th...
Abstract: The templating of the ordered nanostructures of lyotropic liquid crystals (LLC) onto organic polymers has recently been of great interest. This work describes the polymerization and segregation behavior of polar and nonpolar monomers in an LLC environment. Nonpolar monomers partition to the oil-soluble domains of the LLC phase, whereas more polar monomers segregate at the interface of the liquid crystals. The polymerization kinetics in both cases are significantly influenced by the LLC phase morphologies although in different ways. The nonpolar monomers exhibit the fastest polymerization rates in micellar aggregates. This behavior is a result of an increase in the rate of propagation, induced by higher local concentrations of monomer in the micelles as compared to other mesophases. For more polar monomers, the opposite polymerization behavior is observed. The fastest polymerizations for these monomers are observed in the highly ordered lamellar mesophase with the minimum polymerization rate observed in th...
52 citations
TL;DR: Solvent-induced self-assembly of oligomer-substituted shape-persistent macrocycles leads to the formation of cylindrical aggregates, which have been fully characterized in solution and can be described as supramolecular hollow polymer brushes.
Abstract: This work describes the synthesis of a new class of rod-coil block copolymers, oligosubstituted shape persistent macrocycles, (coil-ring-coil block copolymers), and their behavior in solution and in the solid state.The coil-ring-coil block copolymers are formed by nanometer sized shape persistent macrocycles based on the phenyl-ethynyl backbone as rigid block and oligomers of polystyrene or polydimethylsiloxane as flexible blocks. The strategy that has been followed is to synthesize the macrocycles with an alcoholic functionality and the polymer carboxylic acids independently, and then bind them together by esterification. The ester bond is stable and relatively easy to form.The synthesis of the shape persistent macrocycles is based on two separate steps. In the first step the building blocks of the macrocycles are connected by Hagiara-Sogonaschira coupling to form an 'half-ring' as precursor, that contains two free acetylenes. In the second step the half-ring is cyclized by forming two sp-sp bonds via a copper-catalyzed Glaser coupling under pseudo-high-dilution conditions. The polystyrene carboxylic acid was prepared directly by siphoning the living anionic polymer chain into a THF solution, saturated with CO2, while the polydimethylsiloxane carboxylic acid was obtained by hydrosilylating an unsaturated benzylester with an Si-H terminated polydimethylsiloxane, and cleavage of the ester. The carbodiimide coupling was found to be the best way to connect macrocycles and polymers in high yield and high purity.The polystyrene-ring-polystyrene block copolymers are, depending on the molecular weight of the polystyrene, lyotropic liquid crystals in cyclohexane. The aggregation behavior of the copolymers in solution was investigated in more detail using several technique. As a result it can be concluded that the polystyrene-ring-polystyrene block copolymers can aggregate into hollow cylinder-like objects with an average length of 700 nm by a combination of shape complementary and demixing of rigid and flexible polymer parts. The resulting structure can be described as supramolecular hollow cylindrical brush.If the lyotropic solution of the polystyrene-ring-polystyrene block copolymers are dried, they remain birefringent indicating that the solid state has an ordered structure. The polydimethylsiloxane-ring-polydimethylsiloxane block copolymers are more or less fluid at room temperature, and are all birefringent (termotropic liquid crystals) as well. This is a prove that the copolymers are ordered in the fluid state. By a careful investigation using electron diffraction and wide-angle X-ray scattering, it has been possible to derive a model for the 3D-order of the copolymers. The data indicate a lamella structure for both type of copolymers. The macrocycles are arranged in a layer of columns. These crystalline layers are separated by amorphous layers which contain the polymers substituents.
51 citations
TL;DR: In this paper, an efficient and versatile synthesis of a series of polymerizable amphiphilic mesogens that affords control over tail length and position of the polymerizable group is described.
Abstract: An efficient and versatile synthesis of a series of polymerizable amphiphilic mesogens that affords control over tail length and position of the polymerizable group is described. The synthesis employs a novel and facile method of preparing styrene ethers. The monomers are sodium salts of styrene ether-modified fatty acids that can be used to form cross-linkable inverted hexagonal (HII) lyotropic liquid crystal (LLC) phases at ambient temperature with controllable nanometer-scale dimensions. Examination of a series of regioisomers with the same alkyl chain length but with the styrene ether group at different locations along the chain revealed that the position of the styrene ether has a profound effect on the dimensions of the resulting HII phase at a fixed temperature and composition. Increasing overall monomer tail length also has a significant, although smaller, effect on the unit cell dimensions of the LLC phase. By controlling the structure of the LLC monomer in this manner, cross-linked HII phases wi...
TL;DR: In this paper, cross-linked assemblies of lyotropic liquid crystals (LLCs) whose polar termini form ordered channels with enhanced basic or acidic catalytic activity are presented, whose active sites are size-and pH-tunable.
Abstract: Organic frameworks have tempting properties for nanostructured heterogenous catalysts with active sites that are size- and pH-tunable, yet working examples are sparse. The authors present a promising structure type, i.e., cross-linked assemblies of lyotropic liquid crystals (LLCs), whose polar termini form ordered channels with enhanced basic or acidic catalytic activity.
TL;DR: In this article, the authors explore the effect of two liquid crystalline phases on the synthesis of BiOCl, the first being a three-dimensionalally percolated hexagonal liquid crystal, and the second, a two-dimensional percolation lamellar liquid crystal.
TL;DR: The peptide part formed a parallel β-sheet structure in the aggregate, which became tight with the increasing number of Phe residues as discussed by the authors, and the dodecyl chains became disordered when the strong interpeptide hydrogen bonding was formed.
Abstract: N-[11-Trimethylammonioundecanoyl)-O,O‘-didodecyl peptides, whose sequence is Phe-Phe-Glu, Phe-Phe-Phe-Glu, and Phe-Phe-Phe-Phe-Glu, formed an aggregate in CCl4. The peptide part formed a parallel β-sheet structure in the aggregate, which became tight with the increasing number of Phe residues. In contrast, the dodecyl chains became disordered when the strong interpeptide hydrogen bonding was formed. The orderly arrangement of the peptide part disturbed the orderly alignments at the dodecyl chains. Because of the discord between the H-bonding and the chain packing, the peptide-containing amphiphiles possessing more than three amide linkages will form not a crystallite but a lyotropic liquid crystal in CCl4.
Patent•
14 May 2001
TL;DR: In this article, a broad class of Lyotropic liquid crystals of a non-surfactant nature, the so-called lyotropic chromonic liquid crystals (LCLCs), are alignable with the techniques, in particular, LCLCs can be aligned at a surface as one monomolecular layer as a stack of monomeric layers.
Abstract: A broad class of lyotropic liquid crystals of a non-surfactant nature, the so-called lyotropic chromonic liquid crystals (LCLCs), are alignable with the techniques, in particular, LCLCs can be aligned at a surface as one monomolecular layer as a stack of monomolecular layers The method for monolayer alignment is based on alternate layer-by-layer adsorption of polyions and dyes from aqueous solutions that have liquid crystalline structure Using this method, one is able to stack alternate monolayers of dye and polyion while controlling the long-range in-plane orientation of the dye molecules within the plane of each layer The feature of controlling the alignment of LCLCs enables one to create practical devices from them For example, alignment of multilayered stacks allows one to use the resulting dried LCLC films in optical devices, for example, as internal polarizers, color filters, optical compensators, band-gap filters, and the like
TL;DR: The change of mesophases from lamellar to columnar is induced by the change of specific hydrogen bonding patterns from ribbon to disk with the increase of hydrophobic environment.
Abstract: Lipophilic folic acid derivatives exhibit lyotropic liquid-crystalline states in organic solvents The change of the mesophases from lamellar to columnar is induced by the change of specific hydrogen bonding patterns from ribbon to disk with the increase of hydrophobic environment
TL;DR: In this article, the authors examined the thermodynamic behavior of assemblies of flexible and rigid clay plates in both dilute and semidilute concentration regimes and found that the large aspect ratio of the clay implies a long range of interaction at the two particle level.
Abstract: High aspect ratio clay particles dispersed in a lamellar matrix composed of a block copolymer or a lyotropic smectic are expected to orient with the lamellae. Under such conditions, the smectic medium transmits elastic forces among particles in addition to the usual forces produced by dispersion and electrostatic interactions. We compute these elastic forces and explore their influence on the thermodynamics of lamellar-clay dispersions. It turns out that the large aspect ratio of the clay implies a long range of interaction at the two particle level. Consequently, virial expansions break down at very low loadings of particles. We examine the thermodynamic behavior of assemblies of flexible and rigid clay plates in both dilute and semidilute concentration regimes. Our results should have implications for the design of nanocomposites formulated with block copolymers and lyotropic liquid crystals.
TL;DR: In this paper, a mixture of hydrophobic (C6H13O) and hydrophilic (CH3OCH 2CH2OCH2CH2 CH2O) side chains was used to synthesize triphenylenes.
Abstract: 2,3,6,7,10,11-Hexasubstituted triphenylenes have been synthesized that contain a mixture of hydrophobic (C6H13O) and hydrophilic (CH3OCH2CH2OCH2CH2O) side chains. At one extreme HAT6 (1a) (six hydrophobic chains) shows thermotropic behaviour and at the other TP6EO2M (1e) (six hydrophilic chains) shows lyotropic behaviour. Of the triphenylenes with a mixture of hydrophobic and hydrophilic side chains, only the triphenylene with one hydrophilic side chain and five hydrophobic side chains (1b) gives a thermotropic columnar phase. None of the others show liquid crystal behaviour. However, all of these triphenylenes form binary 1:1 compounds when mixed with PDQ9 (2a) and with PTP9 (2b). These CPI (complimentary polytopic interaction) stabilized compounds give thermotropic hexagonal columnar phases over wide temperature ranges.
TL;DR: In this article, deuterium quadrupole splittings from two series of optical isomers, l- and d-N-acyl-1-phenyl-d5-2-aminopropane, with linear acyl chains ranging from 1 to 10 carbon atoms, were measured using 2H NMR spectroscopy.
Abstract: Deuterium quadrupole splittings from two series of optical isomers, l- and d-N-acyl-1-phenyl-d5-2-aminopropane, with linear acyl chains ranging from 1 to 10 carbon atoms, were measured using 2H NMR spectroscopy. Both series of molecules were dissolved in anionic nematic cholesteric lyotropic liquid crystals prepared with cesium N-dodecanoyl-l-alaninate. With these values, the two order parameters that completely characterize the average alignment of the aromatic ring were calculated. Differential incorporation of both series of isomers into the aggregate is observed for intermediate size molecules, as evidenced by the values of the order parameters of the ring. Our results indicate that the first two derivatives in both series, l- and d-C1 and l- and d-C2, are located near the interface, possibly forming a H bond between the NH and/or CO groups and the interstitial water molecules. Increasing the hydrophobicity of the chain by adding one carbon atom induces a decrease in the overall alignment. Intermediat...
TL;DR: In this paper, the shape of cubic lyotropic liquid crystal (V1) is studied in droplets of the mixture C12676/6/water surrounded by water vapor of controlled pressure p. Shapes of monocrystals depend on the conditions of growth from the lamellar phase and on the nature of the substrate.
Abstract: Monocrystals of the cubic lyotropic liquid crystal phase V1 are studied in droplets of the mixture C
12
EO
6/water surrounded by water vapor of controlled pressure p. Shapes of monocrystals are found to depend on the conditions of growth from the lamellar phase and on the nature of the substrate. After the growth, when the lamellar phase is exhausted and crystals are in equilibrium with water vapors, their shapes are shown to depend on the pressure p. Thermodynamic aspects of these phenomena are discussed.
TL;DR: In this article, the glucidic moiety and the hydrophobic alkyl chain are separated by spacer arm E (E=glyceryl, (OEt) 2 -α-polypropyleneglycyl and butyloxy).
TL;DR: In this article, a column is composed of a complex of the α-helical polymer with the corresponding amount of amphiphilic solvent, and packed laterally into a two-dimensional hexagonal lattice.
Abstract: Poly(γ-octadecyl-L-glutamate) with an α-helical rod surrounded by aliphatic side chains can form a lyotropic columnar hexagonal phase when dissolved in amphiphilic solvents, such as octadecylamine, octadecanoic acid, and octadecanol. This novel liquid-crystalline phase is formed in a polymer concentration region of 50 to 82.5 wt.-% and transforms into the well-known cholesteric phase on heating. The column is composed of a complex of the α-helical polymer with the corresponding amount of amphiphilic solvent, and packed laterally into a two-dimensional hexagonal lattice. The homogeneity of the solutions is ensured by the complete miscibility of the octadecyl groups in both the polymer and the solvent, but in this particular case the polar head groups of the solvent are compartmentalized out of the aliphatic domain composed of octadecyl groups. Such a segregated structure attaches the nature of a rod-like column or micelle to each polymer and stabilizes the columnar hexagonal phase. In contrast to the amphiphilic solvent system, the polymers dissolved in a simple octadecane show the usual phase behavior including only the cholesteric mesophase.
01 Jun 2001
TL;DR: In this article, a new submicron film retarder is produced by the deposition and drying of water-based lyotropic liquid crystal materials on various substrates, which have high refraction coefficient anisotropy.
Abstract: New submicron film retarders are produced by the deposition and drying of water-based lyotropic liquid crystal materials on various substrates. The coatings have high refraction coefficient anisotropy. Birefringence varies from 0.5 to 1.0 for 380–900nm wavelength range. These materials provide new options for LCD designs.
TL;DR: It is proposed that the amphiphilic sugar derivatives act like antennae to transfer chirality information and their effectiveness as chiral dopants is due to a hydrophobic anchoring within the micelles and an extension of their chiral moiety far into the intermicellar region.
TL;DR: In this article, an organic lyotropic liquid crystal with long-range structural order was used as template to assemble inorganic/organic hybrid by doping pre-fabricated Ag nanoparticles.
Abstract: The organic lyotropic liquid crystal with long-range structural order is used as template to assemble inorganic/organic hybrid by doping pre-fabricated Ag nanoparticles. The lamellar hybrid with both hydrophilic and hydrophobic particles doped simultaneously is realized for the first time. The change of template structure after doping and the stability origin of dual-doped system are characterized by small angle X-ray scattering and polarized optical microscopy. Results show that the interaction and space matching between surfactant bilayers and doped particles are key factors to obtain stable hybrid.
Patent•
11 May 2001TL;DR: In this article, a method for bulk alignment of LCLCs is proposed based on a unidirectional treatment of the aligning substrate such as a polymer layer, which enables one to create practical devices from them.
Abstract: A broad class of lyotropic liquid crystals of a non-surfactant nature, the so-called lyotropic chromonic liquid crystals (LCLCs), are alignable in bulk. LCLCs can be aligned in bulk as a uniform liquid crystalline monodomain within a closed cell. The method for bulk alignment of LCLCs is based on a unidirectional treatment of the aligning substrate such as a polymer layer. The feature of controlling the alignment of LCLCs enables one to create practical devices from them. For example, bulk alignment of LCLCs allows one to use them in detection and amplification of ligands.
TL;DR: In this paper, the spatial variation of the phase director in an unoriented lamellar liquid crystal is investigated by 2H two-dimensional and one-dimensional exchange and PGSE NMR.
Abstract: The spatial variation of the phase director in an unoriented lamellar lyotropic liquid crystal is investigated by 2H two-dimensional and one-dimensional exchange and PGSE NMR. Exchange NMR probes the single-particle orientational correlation function of D2O molecules that diffuse among regions with different director orientations. The obtained correlation time and the water diffusion coefficient, measured by 2H PGSE NMR, provide the persistence length of director orientation that is defined as domain size. The nature of spatial variation is revealed by the decay of the 2H stimulated echo signal recorded with different evolution times. The persistence length of the director is found to be strongly dependent on the rate of cooling the sample from its isotropic phase.
TL;DR: In this paper, the authors investigated the stability of the lamellar lyotropic liquid crystals using a thermodynamic formalism, where the interfacial tension was expressed in terms of the thickness of the two kinds of lamellae and the effect of bending modulus and ionic strength on the stability was examined.
Abstract: The stability of lamellar lyotropic liquid crystals was investigated using a thermodynamic formalism. The interfacial tension A was expressed in terms of the thicknesses ‰1 and ‰2 of the two kinds of lamellae. For given thicknesses, the system might be stable if A g 0. In adition, the derivatives @f/@‰i of the excess free energy f, due to van der Waals, hydration, steric, electrostatic, and undulation interactions, must be negative for the lamellar structure to be stable. The thermodynamic conditions employed show that the domain of existence of the lamellar phase is restricted to narrow ranges of layer thicknesses and parameters of interaction. The effect of the bending modulus and of the ionic strength on the stability was examined. The thicknesses of the two kinds of lamellae were calculated using equilibrium and mass balance equations. It was shown that the nonlinearity of these equations could be responsible for the observed deviations from the “ideal dilution law”. A comparison between the calculated and experimental results was made.
Patent•
30 Mar 2001
TL;DR: In this paper, an alignment of a lyotropic liquid crystal and an optically anisotropic material having a shape such that an aspect ratio is at least 2 is employed to avoid aggregation.
Abstract: PROBLEM TO BE SOLVED: To form by simply inducing anisotropic alignment a useful optically anisotropic thin film with an optical anisotropic material kept stably dispersed without causing aggregation SOLUTION: The lyotropic liquid crystal composition comprising a lyotropic liquid crystal and, dispersed therein, an optically anisotropic material having a shape such that an aspect ratio is at least 2 is employed The lyotropic liquid crystal and the optically anisotropic material are aligned by shear stress on coating