Showing papers on "Lyotropic liquid crystal published in 2004"

Diffusion-diffusion correlation and exchange as a signature for local order and dynamics

Abstract: We demonstrate the use of new two-dimensional nuclear magnetic resonance experiments in the examination of local diffusional anisotropy under conditions of global isotropy. The methods, known as diffusion-diffusion correlation spectroscopy and diffusion exchange spectroscopy, employ successive pairs of magnetic field gradient pulses, with signal analysis using two-dimensional inverse Laplace transformation. Diffusional anisotropy is measured for water molecules in a polydomain lamellar phase lyotropic liquid crystal, 40 wt % nonionic surfactant C10E3 (C10H21O(CH2CH2O)6H) in H2O.

Microemulsion Liquid Crystal Templates for Highly Ordered Three-Dimensional Mesoporous Silica Monoliths with Controllable Mesopore Structures

Abstract: Nanostructure composite silica monoliths (HOM-n) with three-dimensional (3-D) structures and controllable pore size were fabricated by using microemulsion lyotropic liquid crystal mesophase as templates under acidic conditions. By addition of alkanes with different molecular size (C6-C19 alkyl chains) into the primary lyotropic liquid crystal mesophase of Brij 56 (C16EO10), quaternary microemulsion liquid crystal phases formed and the mesophase topology of the surfactant was significantly enhanced with 3-D structures. Hydrocarbon molecular size and the degree of solubilization significantly influenced the amphiphilic phase behavior and the mesopore morphological structure. The phase transitions between the different cubic symmetries could be controlled by using a different solubilizing agent in the microemulsion phases of Brij 56 amphiphile. Thereby, the phase transition of primary liquid crystal mesophases in the microemulsion systems were used to fabricate well-defined highly ordered mesoporous silica m...

Heterogeneous catalysis using a nanostructured solid acid resin based on lyotropic liquid crystals.

Abstract: The catalytic reactivity and selectivity of the first example of a nanostructured solid acid resin (1) are described. This new type of solid acid catalyst is formed by the self-assembly and copolymerization of two acidic lyotropic liquid crystals (LLCs), affording a columnar hexagonal polymer network with monodisperse nanochannels lined with sulfonic acid groups. The performance of this material as a heterogeneous catalyst was compared against that of two commercially available, amorphous sulfonic acid resins: Amberlyst-15 and Nafion NR50. Using the acid-catalyzed esterification of benzyl alcohol with 1-hexanoic acid in dry toluene as a test reaction, it was found that resin 1 displayed only slightly lower overall reactivity as compared to Amberlyst-15 and Nafion NR50 but more than an order of magnitude higher selectivity for the desired ester product over dibenzyl ether side-product. Control experiments revealed that the higher product selectivity is not due to differences in relative acidity between th...

Lyotropic Liquid Crystals as Nanoreactors for Nanoparticle Synthesis

Abstract: A new methodology for the synthesis of nanoparticles using lyotropic liquid crystals as nanoreactors has been developed. The hydrophilic and hydrophobic domains of lyotropic phases have characteristic dimensions of 2-10 nm and thus can be used to confine reactants that are selectively soluble in only one domain to nanoscopic dimensions. Here, synthesis of Bi (a metal) and PbS (a compound semiconductor) nanoparticles is driven by bringing together reactants via the shear mixing of two liquid crystals, each containing dissolved reactants that are selectively soluble in one of the two phases, as proof-of-principle for this method. Modulating the phase of the lyotropic liquid crystals allows control over the geometry and interconnectivity of the nanoreactors, giving control over the diameter of nanoparticles produced. Decreasing concentration of precursors is shown to decrease particle size. It is also demonstrated that the nanoparticles produced are not agglomerated in the lyotropic liquid crystal during synthesis. The synthesized nanoparticles are characterized with TEM, electron diffraction, EDAX, and UV-Vis-NIR spectroscopy.

Cubatic liquid-crystalline behavior in a system of hard cuboids.

Abstract: The lyotropic phase behavior of cuboidal particles was investigated via Monte Carlo simulations. Hard cubes were approximated by suitably shaped clusters of hard spheres. Changes in concentration and structure of the system were monitored as a function of osmotic pressure P* (imposed in an isobaric ensemble). As expected, an isotropic phase prevailed at low concentrations (low P*) and a crystalline phase formed at high concentrations (high P*). A third distinct phase was also observed for an intermediate range of concentrations (approximately marked by breaks in the P* versus concentration curve). The structure of this mesophase was characterized both visually and analytically by calculating radial distribution functions and order parameters. It was found that such a mesophase exhibits orientational ordering along three axes (cubatic order) but significant translational disorder, thus having a structure clearly distinct from both isotropic and crystalline phases.

Temperature and concentration effects on supramolecular aggregation and phase behavior for poly(propylene oxide)-b-poly(ethylene oxide)- b-poly(propylene oxide) copolymers of different composition in aqueous mixtures, 1.

Abstract: The phase behavior (temperature vs composition) and microstructure for the two binary systems Pluronic 25R4 [(PO)19(EO)33(PO)19]-water and Pluronic 25R2 [(PO)21(EO)14(PO)21]-water have been studied by a combined experimental approach in the whole concentration range and from 5 to 80 degrees C. The general phase behavior has been identified by inspection under polarized light. Precise phase boundaries have been determined by analyzing 2H NMR line shape. The identification and microstructural characterization of the liquid crystalline phases have been achieved using small-angle X-ray scattering (SAXS). The isotropic liquid solution phases have been investigated by self-diffusion measurements (PGSE-NMR method). 25R2 does not form liquid crystals and is miscible with water in the whole concentration range; with increasing temperature, the mixtures split into water-rich and a copolymer-rich solutions in equilibrium. 25R4 shows rich phase behavior, passing, with increasing copolymer concentration, from a water-rich solution to a lamellar and copolymer-rich solution. A small hexagonal phase, completely encircled in the stability region of the water-rich solution, is also present. In water-rich solutions, at low temperatures and low copolymer concentrations, the copolymers are dissolved as independent macromolecules. With increasing copolymer concentrations an interconnected network of micelles is formed in which micellar cores of hydrophobic poly(propylene oxide) are interconnected by poly(ethylene oxide) strands. In copolymer-rich solutions water is molecularly dissolved in the copolymer. The factors influencing the self-aggregation of Pluronic R copolymers (PPO-PEO-PPO sequence) are discussed, and their behavior in water is compared to that of Pluronic copolymers (PEO-PPO-PEO sequence).

Controllable Morphology Formation of Gold Nano- and Micro-plates in Amphiphilic Block Copolymer-based Liquid Crystalline Phase

Abstract: A new and simple method is used to control formation of gold nanoparticles in lyotropic liquid crystal. Triangular or hexagonal nano- and micro-plates can be obtained in PEO–PPO–PEO-based hexagonal...

Highly Ordered Mesoporous Ni Particles Prepared by Electroless Deposition from Lyotropic Liquid Crystals

Abstract: Highly ordered mesoporous Ni particles have been prepared by electroless deposition using lyotropic liquid crystals as templates. The bath conditions, in particular the kind of the reducing agents, greatly affected the degree of the ordering of mesostructures. By using well chosen appropriate reducing agents and combining those agents, we have succeeded in synthesizing Ni particles with highly ordered mesoporosity.

Nonracemic dopant-mediated hierarchical amplification of macromolecular helicity in a charged polyacetylene leading to a cholesteric liquid crystal in water.

Abstract: Here we show the first example of a helical polyacetylene that forms a lyotropic liquid crystal (LC) through a hierarchical amplification of a macromolecular helicity process in water. The macromolecular helicity with an excess of one helical sense was first induced in the positively charged polyacetylene upon complexation with an extremely small oppositely charged nonracemic dopant through electrostatic interaction in water. Subsequently, the helicity was significantly amplified in the polymer backbone as an almost perfect single-handed helix through self-assembly into supramolecular helical arrays in a lyotropic cholesteric state. The present results will allow the detection of a tiny imbalance in chiral molecules and also provide new approaches for the design of novel water-soluble helical architectures and the construction of new chiral materials in areas such as biotechnology and materials science.

Sulfoderivatives of acenaphtho[1,2-b]quinoxaline, lyotropic liquid crystal and anisotropic film on their base

Abstract: The present invention provides a series of new chemical compounds, lyotropic liquid crystal systems, materials, blends, mixtures, namely acenaphtho[1,2-b]quinoxaline sulfoderivatives of the general structural formula: wherein n is an integer in the range of 1 to 4; m is an integer in the range of 0 to 4; z is an integer in the range of 0 to 6, and m+z+n = 10; X and Y are individually selected from the group consisting of CH3, C2H5, OCH3, OC2H5, Cl, Br, OH, OCOCH3 NH2, NHCOCH3, NO2, F, CF3, CN, OCN, SCN, COOH, and CONH2; M is a counterion; and j is the number of counterions in the molecule.

Glassy Crystalline State and Water Sorption of Alkyl Maltosides

Abstract: A differential scanning calorimetric and sorption calorimetric study of two alkyl maltosides, C(8)G(2) and C(10)G(2), was performed. In the dry state, C(8)G(2) and C(10)G(2) do not form solid crystals but undergo a glass transition upon temperature change. The glass is partly ordered and has the same lamellar structure as the liquid crystals formed by the two maltosides. To reflect the presence of the glass transition and the structure, the terms "glassy crystals" and "glassy liquid crystals" can be used. A mechanism of the relaxation of the glassy crystals based on the results of small-angle X-ray scattering experiments is proposed. Experiments on water sorption showed that the glassy crystals turn into lyotropic liquid crystals upon sorption of water at constant temperature. This isothermal glass transition can be characterized by water content and change of partial molar enthalpy of mixing of water. A method to calculate the phase diagram liquid crystals-glassy liquid crystals is proposed. (Less)

Aqueous cholesteric liquid crystals using uncharged rodlike polypeptides.

Abstract: The aqueous, lyotropic liquid-crystalline phase behavior of the α-helical polypeptide, poly(Ne-2-[2-(2-methoxyethoxy)ethoxy]acetyl-lysine) (1), has been studied using optical microscopy and X-ray scattering. Solutions of optically pure 1 were found to form cholesteric liquid crystals at volume fractions that decreased with increasing average chain length. At very high volume fractions, the formation of a hexagonal mesophase was observed. The pitch of the cholesteric phase could be varied by a mixture of enantiomeric samples L-1 and D-1, where the pitch increased as the mixture approached equimolar. The cholesteric phases could be untwisted, using either magnetic field or shear flow, into nematic phases, which relaxed into cholesterics upon removal of field or shear. We have found that the phase diagram of 1 in aqueous solution parallels that of poly(γ-benzyl glutamate) in organic solvents, thus providing a useful system for liquid-crystal applications requiring water as solvent.

Formation of Thermotropic and Lyotropic Liquid Crystals of Bis(N‐alkylethylenediamine)silver(I) Nitrate

Abstract: We have synthesized bis(N-hexylethylenediamine)silver(I) nitrate ([Ag(hex-en)2]NO3), bis(N-octylethylenediamine)silver(I) nitrate ([Ag(oct-en)2]NO3), and bis(N-dodecylethylenediamine)silver(I) nitrate ([Ag(dod-en)2]NO3) and investigated the aggregation behavior of [Ag(dod-en)2]NO3 and [Ag(oct-en)2]NO3 in the liquid state. An X-ray crystallographic analysis revealed that [Ag(dod-en)2]NO3 has a dinuclear structure in the crystalline state — the molecular composition unit is [Ag2(dod-en)4](NO3)2, where the two dod-en ligands bridge two silver ions that are coordinated by four nitrogen atoms. The dinuclear complex is appreciably dissociated into a mononuclear complex in solution. It was found that [Ag(oct-en)2]NO3 and [Ag(dod-en)2]NO3 form thermotropic liquid crystals in the temperature ranges 48−67 °C and 59−96 °C, respectively, and a lyotropic liquid crystal was also observed for [Ag(dod-en)2]NO3 in n-heptane at around room temperature in the presence of a small amount of water. The structures of the thermotropic and lyotropic liquid crystals of [Ag(dod-en)2]NO3 were identified as a typical smectic A (SA) type and a nematic one, respectively. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Advances in NMR Studies of Liquid Crystals

Abstract: Recent solid state NMR studies of liquid crystalline materials are surveyed. The review deals first with some background information in order to facilitate discussions on various NMR ( 13 C, 1 H, 2 H, 19 F etc.) works to be followed. This includes the following: spin Hamiltonians, spin relaxation theory, and a survey of recent solid state NMR methods (mainly 13 C) for liquid crystals on the one hand, while on the other hand molecular ordering of mesogens and motional models for liquid crystals. NMR studies done since 1997 on both solutes and solvent molecules are discussed. For the latter, thermotropic and lyotropic liquid crystals are included with an emphasis on newly discovered liquid crystalline materials. For the solute studies, both small molecules and weakly ordered biomolecules are briefly surveyed.

Perylenetetracarboxylic acid dibenzimidazole sulfoderivatives containing oxo-groups in the perylene core which form part of a para-quinoid system of bonds, lyotropic liquid crystal systems and anisotropic films containing the same, and methods for making the same

Abstract: Anisotropic films based on sulfoderivatives of perylenetetracarboxylic acid dibenzimidazole (PTCA DBI) which contain oxo groups pendant to a perylene core. The oxo-groups, in combination with portions of the perylene core, form a quinoid system of bonds. The oxo substituted PTCA DBI sulfoderivatives form liquid crystal systems possessing high optical properties. Said liquid crystal systems can be applied onto various substrates to obtain optically isotropic or anisotropic, at least partially crystalline, films applicable in various fields.

Platinum Thin Film with a Highly Ordered Mesostructure by Contact Plating

Abstract: By a contact plating technique using a galvanic reaction between Al and An in the presence of Pt complex, we have for the first time succeeded in the formation of a highly ordered meso-structured Pt film on a An surface by reduction of Pt ions in the presence of lyotropic liquid crystals.

Measurements of optical anisotropy of a calamitic lyotropic liquid crystal

Abstract: Optical birefringence measurements for a calamitic lyotropic liquid crystal containing sodium lauryl sulphate/decanol/water are presented. A value of the order of 10-3 was obtained, much smaller than that of thermotropic liquid crystals. The order parameter temperature dependence is evaluated using an extrapolating method and taking into accounts the influence of the micelle shape. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Lyotropic Chromonic Liquid Crystals for Optical Applications – an Optical Retardation Plate for Twisted Nematic Cells

Abstract: An aqueous solution of disodium cromoglycate (cromolyn) is known to form the chromonic N phase (i.e. a nematic lyotropic columnar phase) at room temperature and concentration range 13–17%, and the corresponding N∗ twisted nematic phase if chiral dopants are added. We have produced lyotropic liquid crystal films and cells with a uniform planar alignment and cells with twisted optic axis using L amino acids as chiral dopants. The optical retardation of the lyotropic twisted nematic (TN) cells was chosen to match that of active TN cells in the normally black (NB) TN device. When two cells are placed together between crossed polarizers, the birefringence effects cancel for all viewing directions, thus providing achromatic dark state, high head-on contrast, and a wide viewing cone.

Study of the water conformation around hydrophilic and hydrophobic parts of styrene-maleic anhydride

Abstract: The influence of shells of water on the conformation of the monomer of poly(styrene-maleic anhydride) was studied using explicit solvent models. The molecule possesses a hydrophobic and a hydrophilic group which allows the determination of the influence of the water orientation around both the hydrophilic and hydrophobic groups. The hydrophilic interactions were found to be direct and long range, whereas the hydrophobic interactions were found to be indirect and short range. Because the hydrophobic interactions are indirect, they can be repetitively applied and optimised to large structures such as polymers.

Lyotropic liquid crystals i. specific structures

Abstract: This review synthesizes the most valuable recent i nformation on lyotropic liquid crystals topic, laying on 70 international publications. It presents a general description of the lyotropic behavior from the micellisation process to the specific liquid crystals ordered structures conception. Thermodynamic c onditions are detailed too. A succinct classificati on of the lyotropic liquid crystals, upon both geometrical configuration of the structures and the hydrocarbon chain conformation, is also presented.

Enantiomeric discrimination of water soluble compounds using deuterium NMR in a glucopon/buffered water/n-hexanol chiral lyotropic liquid crystal

Abstract: Enantiomers of water soluble materials can be observed using deuterium NMR spectroscopy in the lyotropic mesophase formed by glucopon/hexanol/buffered water. The orientational properties of this mesophase is evaluated and the dependence of the enantiomeric discrimination on the temperature and the composition of the mesophase is studied.

Functionalized nanostructured lyotropic liquid crystal polymers

Abstract: The invention provides cross-linked lyotropic liquid crystal (LLC) copolymers having ordered nanometer-sized pores lined with functional groups. The copolymers are formed by copolymerizing LLC monomers with strong LLC character and functionalized monomers with no or weak LLC character to form an LLC phase. Both the LLC monomers and the functionalized monomers contain hydrogen-bonding groups and hydrogen-bonding is believed to assist in the formation of the LLC phase of the blended mixture. Different classes of functional groups useful for the invention include, but are not limited to, acidic groups, basic groups, catalytic groups, oxidizing agents, reducing agents, polymerization initiators, binding agents, optically active groups, and electrically active groups. The invention also provides methods for making the cross-linked LLC copolymers of the invention. In these methods, the LLC monomer and the functionalized monomer are blended in a polar solvent, thereby allowing self-assembly of the first and second monomer into an LLC phase. The LLC phase in then cross-linked with retention of the LLC microstructure.

Macroporous Gels of Poly(N,N-dimethylacrylamide) Obtained in the Lamellar System AOT/Water

Abstract: N,N-Dimethylacrylamide and N,N‘-methylenebis(acrylamide) are copolymerized in the lyotropic AOT/water medium to yield several types of macroporous hydrogels. These gels are formed in two different macroscopic phases of the reacting system. The morphology of the gels, once isolated, is widely different depending on the macroscopic phase in which they were formed. Inside each phase, the polymerization induces an additional microscopic phase separation, with the result of deswelling of the original lamellar AOT/water structure. The morphology of the isolated gels is not a copy of this original nanostructure, instead, it has features whose length scales are larger than those of the starting phases. More complex morphological patterns develop in the presence of surfactant, as a result of the phase separation process. The type of morphology appears to be correlated with the proportion of water contained in the macroscopic phases. The swelling of the isolated gels in water does not follow the increase with chain...

NMR Studies of 13C-Iodomethane: Different Behavior in Thermotropic and Lyotropic Liquid Crystals

Abstract: High-resolution NMR spectra of 13C-iodomethane dissolved in thermotropic and lyotropic liquid crystalline solvents have been used to measure 1H−1H and 13C−1H dipolar couplings. The ratio of these two couplings, which is a function of the H−C−H bond angle in 13C-iodomethane, is, in general, different from that expected from the known molecular structure; solvent−solute interactions in liquid crystalline solutions are responsible for this difference. In thermotropic liquid crystalline solutions, the apparent bond angle deviation (Δθa) increases with decreasing molecular ordering. In contrast, in lyotropic liquid crystals, no significant spectral aberration has been observed. These results indicate a fundamental physicochemical difference between the intermolecular interactions that prevail in thermotropic and lyotropic liquid crystals.