Supramolecular liquid crystals displaying competitive hydrogen bonding: Small molecule mesogens assembled through different hydrogen bond assemblies

A series of supramolecular assemblies created through competitive hydrogen bonding of a n-alkoxy benzoic acid hydrogen bond donor and a mixture of hydrogen bond acceptors: a liquid crystal-forming rigid bi-pyridyl and a non-mesogenic tetrafunctional pyridyl species. The associative chain structures displayed mesogenic characteristics at loadings dependent on the concentration of the disruptive tetrafunctional agent- systems eliminated liquid crystallinity at 85% inclusion in heating transitions and 90% in cooling. The assembled structures displayed considerable mesophase stability. This was observed through long liquid crystalline lifetimes even at high compositions of 4PD, which generally dampened due to a generalized eutectic effect. It is believed that the freedom of mobility inherent in the C8 Acid allows for the reorganization of the hydrogen bonds in the liquid crystalline state providing for a very high loading of disruptor and long mesophase lifetimes.     

Design,Synthesis and Analysis of Chlorohydroquinone Derivatives—Liquid Crystalline Complexes

A novel linear double hydrogen-bonded liquid crystalline material is designed and isolated. The ingredients of the mesogens synthesized are chloro hydroquinone (ClHQ) and p-n alkyloxy benzoic acid (nBAO) where n varied from pentyl to dodecyl alkyloxy carbon numbers. The series is abbreviated as ClHQ + nBAO, and seven of eight synthesized complexes are found to exhibit liquid crystalline phases. These liquid crystalline complexes are characterized by Fourier Transformation Infrared spectroscopy (FTIR) in order to confirm the formation of hydrogen bond. Mesophases and their corresponding transition temperatures are studied by polarizing optical microscopy (POM) and their respective enthalpy values along with the order of the transitions are determined by Differential Scanning Calorimetry (DSC). The experimental measurement of tilt angle is carried out by optical extinction method and fitted to the theoretically predicted mean field exponent which is found to be in good agreement. Dielectric relaxations at different temperatures in nematic phase for the complexes have been carried out and their corresponding activation energy values are calculated from Cole–Davidson plots. Light filtering action in the liquid crystalline complexes is done to validate the commercial applications of these mesogens.     

Synthesis,characterization of new carboxylic acid derivatives bearing 1,3,4-thiadiazole moiety and study their liquid crystalline behaviors

Thirteen carboxylic acid derivatives containing 1,3,4-thiadiazole ring in their core and swinging alkoxy terminal were synthesized. They were characterized by ¹H, ¹³C NMR spectroscopy, FTIR, and mass spectrometry. Their liquid crystalline behaviors have been studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The 1,3,4-thiadiazole compounds in this study were 2,5 di-substituted asymmetrical, alkoxy, and carboxy linkages. The compounds with alkoxy of long carbon chains (n > 7) displayed Smectic C phase. The liquid crystal properties were found to be affected by the length of alkoxy chain attached to the phenyl moiety and the two types of the dimeric form were resulted from the hydrogen bonding interaction between carboxylic acid molecules.     

Preparation and characterizations of bulk GaN crystals

The growth conditions and mechanism of hexagonal GaN platelet crystals by Li flux were studied. The experimental results confirmed that these crystals crystallized from Li–Ga–N liquid phase. Photoluminescence (PL) spectra and Raman scattering spectrum of the crystals were obtained, which show that GaN crystals obtained by this method possess good crystalline quality.     

Amorphous metal-hydrogen alloys prepared by mechano-chemical reaction

The mechano-chemical formation of crystalline and amorphous hydrides is described. Niobium transformed into β-Nb hydride by milling with liquid normal-heptane. Chromium and manganese were transformed into amorphous hydrides. The hydrocarbon served as the source of hydrogen atoms through a dehydrogenation reaction.     

Preparation of Stable Anisotropic Films with Columnar Order from Polymerizable Star-shaped Supramolecular Liquid Crystals

We have fabricated new stable anisotropic films with columnar order using star-shaped supramolecular liquid crystals as photoreactive monomers. The polymerizable supramolecular liquid crystal exhibiting a hexagonal columnar mesophase has been prepared simply through hydrogen bonding between a phloroglucinol core and pyridine derivatives containing acrylate groups in the alkyl chain. Photopolymerization of the supramolecular monomer in the liquid crystalline state yielded cross-linked anisotropic polymer networks with columnar order. The controlled approach in the present study opens a new way to design and prepare stable anisotropic materials for potential electronic and optical applications.     

Supramolecular Discotic Columnar Liquid Crystals Built through Single Hydrogen Bonding between Carboxylic Acid and Pyridine Moieties

New self-assembled discotic columnar liquid crystals were prepared via single hydrogen bonding between the core molecule of 1,3,5-cyclohexanetricarboxylic acid and the peripheral units of stilbazole derivatives. The hydrogen-bonded liquid crystals exhibited rectangular columnar and hexagonal columnar mesophases depending on the number of alkyl chains in three arms of the discotic mesogen through dipole-dipole interactions between carbonyl groups along the column axis. The intermolecular hydrogen bonding between carboxylic acid and pyridine moieties provides an effortless methodology to prepare the ordered columnar liquid crystals for electronic applications.     

不同磷源制备磷酸铋及其光催化性能研究

三种不同磷源在超声作用下制备磷酸铋,磷酸氢二钠为磷源制备棒状磷酸铋,咪唑磷酸盐离子液为磷源制备梭状磷酸铋,三乙烯四胺磷酸盐离子液为磷源制备颗粒状磷酸铋.XRD表征分析表明三乙烯四胺磷酸离子液为磷源制备的磷酸铋衍射峰最高,咪唑磷酸盐离子液制备磷酸铋次之,磷酸二氢钠制备的磷酸铋衍射峰最低.紫外-可见分析表明离子液中合成的磷酸铋向低波数发生移动.BET分析表明在磷酸二氢钠、咪唑磷酸盐、三乙烯四胺磷酸盐中合成的磷酸铋的比表面积分别为3.9472 m2/g,11.548 m2/g和24.063 m2/g.三种磷酸铋在紫外光下对亚甲基蓝匀有光催化作用,其中三乙烯四胺磷酸盐离子液为磷源制备的磷酸铋光催化性能最佳,同时考察了三乙基四胺磷酸盐离子液制备磷酸铋以及光催化的条件.     

Influence of Naphthalene Moiety on Mesomorphism

Compounds containing naphthalene moiety are synthesized and the liquid crystalline properties studied by texture observations. The mesomorphic properties of these compounds are compared with related compounds to understand the influence of broad units such as naphthalene on mesomorphism. It is observed that there is a limit to which the end alkoxy group can be extended in a mesogen. The method of preparation, and properties of these compounds are given.     

On the electrochemical behaviour of undercooled melts and glasses

The electrochemical behaviour of undercooled melts and glasses is considered in detail. First the thermodynamic properties of the corresponding phases are calculated and then the temperature course of the emf and of other thermodynamic functions of a galvanic cell in which the net reaction is: undercooled melt (glass)→crystal, are determined. Some additional problems concerning the electrochemistry of amorphous electrodes are analyzed, e.g. hydrogen overvoltage upon hydrogen evolution on crystalline or amorphous electrodes of a given metal. Several variants are discussed for the possible experimental realization of a galvanic cell in which the emf is determined by the difference in the chemical potentials of the undercooled melt (or the glass) and the crystal, i.e. of a galvanic cell with a vitreous and a crystalline electrode made of one and the same electronic conductor or of a bipolar cell with an amorphous and a crystalline electrolyte, etc. An attempt is made to estimate the interal electric (Galvani) potential at the melt/crystal interface by using data for the difference of the Peltier coefficient between the respective phases.The analysis of the electrochemical behaviour of vitreous, liquid and crystalline electrodes is performed on the basis of formal thermodynamics and in terms of classical model approaches. It is shown how to determine by electrochemical measurements the main thermodynamic parameters of glasses which are considered as frozen-in non-equilibrium systems.     

Solubility and crystallization of BaHPO4 crystals

A study of growth of barium hydrogen phosphate (BaHPO₄) crystal from solution is reported. The raw materials of barium hydrogen phosphate were successfully synthesized through chemical reaction in water. The solubility in HCl and H₃PO₄ solution were studied. It increased when acid concentration and temperature become higher, and the fitted curve of solubility is nearly a line. The acid concentration affects crystalline morphology of BaHPO₄ crystal. The crystallization is well when the acid solution ranges from 0.5 to 0.8M. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

The relation between deep trapping levels and the structure of Se layers

Using electron microscopy methods it has been determined that there are numerous crystalline inclusions in evaporated layers of amorphous selenium. The density, dimensions, modification and distribution in the cross section of a layer are essentially dependent upon the method of layer preparation. The maximum micro-inclusion density is observed in layers evaporated at a substrate temperature (t_s) between 8 to 30°C. These layers also possess crystallites of monoclinic modification. In layers evaporated at t_s ? 50°C inclusions of trigonal modification prevail.The parameters of the deep trapping levels for holes and electrons have been determined from photodischarge kinetics. The origin of these levels is found to be related to the phase transition. The hole traps are caused by the crystalline formation of trigonal modification, and the electron traps by crystallites of monoclinic modification.     

Optical Rotatory Dispersion Measurements of the Liquid Crystalline Blue Phases in Thick Layers

The results of optical rotatory dispersion (ORD) measurements in liquid crystalline blue phases (BP) are reported for pure compounds and mixtures. They have been performed on polycrystalline samples (thick layers). Two features distinguish their spectra from those obtained from liquid single crystals:

(1) The magnitude of the rotation is much smaller, and

(2) no sharp anomalous ORD region is present.

The spectra possess a weak, broad anomalous region. Their sign and wavelength dependence follows the sense and pitch of the cholesteric helix. ORD experiments with mixtures of the same cholesteric esters with a nematic substance yield results typical of well oriented samples. The spectra exhibit larger rotation angles and a significantly smaller anomalous region.     

The Synthesis and Characterization of Thermotropic Liquid Crystal Model Compounds

Recently, the unique morphological classification of the “liquid crystal” state has simultaneously aroused the interest of the industrial and scientific community. With this renewed interest has come a need for better understanding and characterization of the liquid crystal transitions which occur within the many polymeric systems exhibiting this morphological phenomenon. Of the seven newly synthesized thermotropic materials for this study which are p-hydroxybenzoic acid modified compounds, six were of the rod-like geometry typically associated with mesogens. The seventh compound, a derivative of pentaerythritol, was cross-shaped and had a crystalline morphology. All compounds, including the p-hydroxybenzoic acid modified mesogenic precursor, were subjected to various characterization techniques such as proton Nuclear Magnetic Resonance (NMR), infrared spectroscopy (IR), and elemental analysis for structure determination, as well as differential scanning calorimetry (DSC), polarising microscopy equipped with a hot stage, and Fischer-Johns apparatus for thermal analysis.

Results of this study reconfirms previous investigations of similar low molecular oligomers with mesogenic forming ability both in terms of the predictable and of the actual range of the thermotropic and thermodynamic transitions. A different morphological state exists for at least two of the compounds which seemed to exhibit both crystalline and liquid crystalline states. The existence of this morphology created the opportunity for comparison of model compounds of this study with that of polyurethanes.     

Liquid crystalline dispersions of double-stranded nucleic acids and their complexes as a background for nanodesign: Review

Different strategies in design of nanoconstructions whose building blocks are both linear molecules of double-stranded nucleic acids and nucleic acid molecules fixed in the spatial structure of particles of liquid crystalline dispersions have been considered.     

Boron clusters as structural elements of novel liquid crystalline materials

closo-Boranes are characterised by high thermal and oxidative stability due in part to highly delocalised bonding within a σ-framework. These boron clusters when employed as structural elements of liquid crystals give rise to novel structures with unique properties and vast potential in applications. The neutral closo-boranes such as the carboranes provide opportunity to perform fundamental structure–property relationship studies that may provide additional insight on the liquid crystalline state. The anionic closo-borates possessing a highly delocalised negative two charge can be used as structural elements of zwitterionic, quadrupolar liquid crystalline materials. Such materials may be of use for understanding the effects of polarity on the liquid crystalline state. Lastly, the anionic closo-monocarbaborates possessing a single highly delocalised negative charge can be envisioned as structural elements of either highly polar or ionic liquid crystalline materials. The highly polar materials may also serve as models for understanding the effects of polarity on the liquid crystalline state. Additionally, they should have application as positive Δ? additives for nematic liquid crystalline mixture formulations. The ionic materials, where the anionic fragment drives liquid crystalline behaviour, lend themselves as potential electrolytes for anisotropic ion transport in battery technologies. The review presented here introduces these concepts and highlights the current status of boron cluster containing liquid crystalline materials.     

高纯TiO2超微粉体的制备

以廉价的TiCl4为原料,液体石蜡为纯化剂,氨水作形核剂,制备出高纯TiO2超微粉体。用XRF分析了样品的物相组成;XRD和SEM等手段表征了粉体合成过程的物相变化和形貌特征。结果表明,TiCl4经过矿物油(液体石蜡)除钒和精馏除铁等杂质后进行水解,当TiCl4溶液浓度0.65 mol/L,水解温度60℃、反应时间2 h、pH值=7、在800℃煅烧2 h条件下,制备出TiO2的纯度达到99.9952%,晶型为金红石相,晶粒尺寸约0.65μm,形貌近球形。     

Computer Simulation of Biphenyl-Phenyl Ester Liquid Crystals

Abstract

Molecular orbital (MO) calculation and molecular dynamics (MD) simulation were carried out for a set of smectic liquid crystalline molecules, 8O-O8 (4-octyloxyphenyl-4′-octyloxybi-phenyl-4-carboxylate) and 8O-8 (4-octylphenyl-4′-octyloxybiphenyl-4-carboxylate), to understand the molecular origin of different crystalline structure formation and to predict their conformational property in liquid crystalline phases. The results of MO and MD analyses indicate that the structure of 8O-O8 and 8O-8 in crystalline phase is essentially determined by intramolecular interactions and the experimentally observed structure is chosen as a consequence of intermolecular packing constraints. This paper also reports the first application of two-molecular ab-initio calculation to liquid crystalline systems.     

Unit cell dimensions and space groups of some liquid crystals

It is now very well established that for a proper understanding and interpretation of several physical properties of liquid crystalline phases, a knowledge of the molecular structure in the crystalline state is very useful, as the molecular conformation in the crystalline state predetermines the molecular organisation inthe mesomorphic state. Also, it is believed that the stabilisation of liquid crystalline phase and hence the micro variations in the physical properties depend strongly on the long side chains and are essentially independent of the central rigid core. In view of this, we communicate the preliminary crystallogrphic data for some liquid crystalline materials, the detailed structure of which has been taken up.     

Contraction of side-on nematic liquid crystalline elastomers micropillars: Influence of molecular parameters

We investigated the structure-property relationship of nematic liquid crystalline elastomer (LCE) actuators obtained from a series of nematic side-on monomers. The liquid crystalline acrylate monomers were designed and synthesized with different tail lengths. Combining a soft lithography technique with photo-polymerization/photo-crosslinking of aligned nematic liquid crystalline monomers and crosslinkers, nematic LCE micropillars were obtained, based on the new monomers. Through microscopic observation, influence of some structural parameters on the thermo-mechanical behavior of the micropillars was investigated. The thermo-mechanical behavior of the LCEs showed a close correlation with to the tail length of the monomer and the spacer length of the crosslinker.