Apolar 2-alkoxyalkoxy-substituted nematic liquid crystals

The synthesis is reported of a series of apolar nematic liquid crystals incorporating an alkoxyalkoxy chain attached in a terminal position to the molecular core. The dependence of the mesomorphism and phase transition temperatures on the nature of the terminal chain with one, two or three oxygen atoms was studied. Some compounds with a completely alicyclic molecular core and a terminal 2-methoxyethoxy chain exhibit a nematic phase with a low melting point, birefringence and viscosity and a relatively high clearing point in the absence of smectic phases. They do not to absorb light in the near UV and may be useful as components of UV-stable nematic mixtures for use in photoluminescent liquid crystal displays. The presence of the methoxyethoxy chain leads to a relatively large dipole moment perpendicular to the molecular long axis.     

Polar 2-alkoxyethoxy-substituted nematic liquid crystals

The synthesis is reported of a series of polar nematic liquid crystals incorporating an alkoxyalkoxy chain attached in a terminal position to a molecular core consisting of two aromatic rings. The dependence of the mesomorphism and phase transition temperatures on the nature of this terminal chain was studied. The shape anisotropy of the core is increased by the presence of an additional 1,4-disubstituted phenyl unit in a number of p-terphenyls. A number of highly polar esters with a terminal methoxyethoxy chain have been prepared as dopants to lower the threshold voltage of LCDs. The presence of the methoxyethoxy chain leads to an increase in the molecular dipole moment, the dielectric anisotropy and the dielectric constant perpendicular to the molecular long axis. Several compounds with a four-unit diether central linkage were also prepared.     

[2]Benzothiophene bent-shaped liquid crystals

New liquid crystalline (LC) compounds containing the [2 Weissflog, W., Nádasi, H., Dunemann, U., Pelzl, G., Diele, S., Eremin, A. and Kresse, H. 2001. J. Mater. Chem., 11: 2748–2758. [Crossref], [Web of Science ®] , [Google Scholar]]benzothiophene chromophore unit have been synthesised and their mesomorphic properties studied. Mesomorphic and fluorescent properties have been modified by various chemical moieties. Among others, terminal fluoroalkyl and/or chiral chains were introduced to stabilise mesophases and support the formation of polar phases. In spite of the bent shape due to the central 1,3-diphenylbenzo[c]thiophene unit, all compounds exhibit phases typical for the rod-like LC: nematic, smectic A and smectic C or their chiral analogues using the chiral (S)-C₂H₅CH(CH₃)(CH₂)₆CO or (S)-C₁₀H₂₁OCH(CH₃)CO chain. The orientational order in the nematic phase was studied by polarised infrared measurements. The fluorescent properties of the studied compounds have been measured and their parameters established.     

Proton-coupled O2 reduction reaction catalysed by cobalt phthalocyanine at liquid/liquid interfaces

Pushed over the edge: Proton-transfer coupled O(2) reduction catalysed by cobalt phthalocyanine ([CoPc]) was studied at the water/1,2-dichloroethane (DCE) interface (see figure). This system represents a new model of molecular electrocatalysis with the proton transfer controlled by the Galvani potential difference and the electron transfer by the molecular properties of the catalyst and electron donor.     

New liquid crystal based on 2-phenylthiophene central core

Six series of bent-shaped liquid crystals based on phenylthiophene central unit and differing in lateral substitution, the number and orientation of ester linkages and character of the terminal chain have been synthesised and studied. In comparison with the previously investigated biphenyl-based analogues, the presence of the thiophene unit results in a strong increase of transition temperatures and appearance of calamitic phases, the character of which depended on the structural changes of mesogens.     

Novel liquid crystal compounds,derivatives of 2-pyrone

6-(4-n-Hexyloxyphenyl)- and 6-(4-n-decyloxyphenyl)-2-pyrones, which possess smectic and nematic mesomorphism, were synthesized.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1793–1794, October, 1994.     

High-performance liquid chromatographic determination of 2-furaldehyde in spirits

Official methods for the determination of 2-furaldehyde in spirits involve for a spectrophotometric evaluation, which is characterized by poor specificity. Gas chromatographic evaluations have also been proposed, which offer a much higher sensitivity, particularly when capillary columns are used. In this paper a high-performance liquid chromatographic (HPLC) method based on the formation of the 2,4-dinitrophenylhydrazones of carbonyl compounds and subsequent reversed-phase separation of these derivatives is described. Derivatization is carried out by utilizing an acidic solution of 2,4-dinitrophenylhydrazine in acetonitrile. Precipitation of the derivatives is avoided, and direct injection of the sample into the HPLC system is allowed. The determination ofrers a high specificity and a detection limit of the order of 10⁻⁸ mol/1. Accuracy and reproducibility data are presented.     

Novel ionic liquid assisted synthesis of SnO2 microspheres

Tin oxide (SnO2) microspheres with an average 2.5 microm in diameters have been successfully synthesized through a rapid hydrothermal process heating by microwave in the presence of an ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate. X-ray diffraction, scanning electron microscopy and transmission electron microscopy are used to characterize the morphology and crystalline structure of the microspheres. The as-synthesized SnO2 microspheres exhibit a tetragonal rutile structure. The mechanism of the microspheres formation is proposed.     

Ionic liquid assisted preparation of nanostructured TiO2 particles

Anatase-containing nanostructured TiO(2) particles with high surface area have been synthesized using a water immiscible room temperature ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) as an effective additional solvent by the sol-gel method at low temperature.     

SO2 gas separation using supported ionic liquid membranes

Measurements of permeability of sulfur dioxide (SO2) in five imidazolium-based ionic liquids supported on the polyethersulfone microfiltration membranes at temperatures from 25 to 45 degrees C and atmospheric pressure indicate that under the same conditions, the SO2 selectivity of separations using supported ionic liquid membranes are 9-19 times that of CO2.     

Electrocarboxylation of 1,4-dibromobut-2-ene in a CO2-DMF liquid mixture

The possibility of synthesizing dihydromuconic acid by cathodic carboxylation of 1,4-dibromobut-2-ene in the liquid CO₂-aprotic solvent system was investigated. The low yield of dihydromuconic acid in this reaction was explained by the competing reductive debromodimerization and oligomerization of 1,4-dibromobut-2-ene, which lead to the predominant formation of 1,8-dibromo-2,6-octadiene and polymeric products. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1637–1641, September, 1997.     

A liquid state Hg(2+)-sensitive electrode

The construction and basic characteristics of a liquid-state Hg(2+)-sensitive electrode are discussed. The membrane consists of the Hg(2+) chelate of diketohydrindylidene-diketohydrindamine (DYDA) in chloroform. The range of linear response of the electrode is 10(-1)-10(-5)M Hg(2+) with a slope of 31 mV/decade. The response time of the electrode is a few seconds in concentrated solutions. The electrode may be used with good results in potentiometric titrations involving Hg(2+).     

Mass transport in sub-2-microm high-performance liquid chromatography

Ultra-high pressure liquid chromatography enables increased separation speed and efficiency. The quantitative improvement in efficiency is lower than that predicted by theory, and the reasons are not known. In this work, slow mass transport due to analyte desorption from the stationary phase is discussed as a possible contribution to the lower than expected efficiency. Data in the literature for the reversed phase elution of acetophenone, for which particle size was varied with constant particle composition and mobile phase, were used to test this possibility. The mass transport terms for the three particles sizes (1.7, 3.5 and 5.0 microm) fit well to a model that includes desorption from the stationary phase as a contribution, and this analysis yields an apparent desorption time constant of 2.0(+/-0.2)ms for acetophenone in a reversed-phase separation. The results indicate that it is reasonable to consider slow desorption as a possible contribution to the reduced plate height for sub-2-microm particles.     

Toward a density functional description of liquid pH2

A finite-temperature density functional approach to describe the properties of parahydrogen in the liquid-vapor coexistence region is presented. The first proposed functional is zero-range, where the density-gradient term is adjusted so as to reproduce the surface tension of the liquid-vapor interface at low temperature. The second functional is finite-range and, while it is fitted to reproduce bulk pH(2) properties only, it is shown to yield surface properties in good agreement with experiments. These functionals are used to study the surface thickness of the liquid-vapor interface, the wetting transition of parahydrogen on a planar Rb model surface, and homogeneous cavitation in bulk liquid pH(2).     

Picosecond calorimetry: time-resolved x-ray diffraction studies of liquid CH2Cl2

Liquid phase time-resolved x-ray diffraction with 100 ps resolution has recently emerged as a powerful technique for probing the structural dynamics of transient photochemical species in solution. It is intrinsic to the method, however, that a structural signal is observed not only from the photochemical of interest but also from the embedding solvent matrix. To experimentally characterize the x-ray diffraction signal deriving from the solvent alone we performed time-resolved diffraction studies of a pure liquid sample over a time domain from -250 ps to 2.5 micros. Multiphoton excitation was used to rapidly heat liquid CH(2)Cl(2) using UV pulses of 100 fs duration. A significant x-ray diffraction signal is visible prior to the onset of thermal expansion, which characterizes a highly compressed superheated liquid. Liquid CH(2)Cl(2) then expands as a shock wave propagates through the sample and the temporal dependence of this phenomenon is in good agreement with theory. An unexpectedly slow initial release of energy into the liquid as heat is observed from multiphoton excited CH(2)Cl(2), revealing the presence of a metastable state of multiphoton excited CH(2)Cl(2).     

Effects of salicylate 2-hydroxybenzoate on ionic liquid N-hexadecane-N-methylpyrrolidinium bromide

Surface tension, steady-shear viscosity, and antibacterial activity were investigated when salicylate 2-hydroxybenzoate (NaSal) was added to the micellar solution of N-hexadecane-N-methylpyrrolidinium bromide (C₁₆MPB). It was found that for the mixed system, two flat portions appeared on the surface tension curve with the existence of NaSal in the low-concentration range. The equilibrium contact angle of droplets was decreased with the increase of NaSal concentration. In addition, the steady-shear viscosity abruptly increased with the increase of the concentration of mixture, even if the concentration of NaSal is low. However, this high-viscosity solution exhibited temperature-sensitive property, and white precipitate formation below 18°C. Moreover, the bactericidal capability of C₁₆MPB was affected severely by the mixture of high concentration. All of these features could be attributed to the special interactions between C₁₆MPB and NaSal molecules, among which intramolecular hydrogen bonding of NaSal plays a key role, which have been primely demonstrated by the package of Gaussian09 in this work.     

Ionic liquid assisted synthesis of flowerlike Cu2O micro-nanocrystals

Novel flowerlike Cu2O micro-nanocrystals were prepared by a greener reductive reaction of cupric acetate monohydrate with ethylene glycol in aqueous solutions of [C8mim]X (X = Cl , Br , BF4 , PF6 ) and [Cnmim][BF4] (n = 4, 6, 8). The obtained microstructures of Cu2O were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR). The effects of cations, anions and concentration of the ionic liquids on the morphology of Cu2O were examined in some details. The results suggest that the formation of flowerlike Cu2O was governed by a [C8mim][BF4] controlled reductive reaction mechanism. As one of their applications, the Cu2O nanoparticles were used for the photocatalytic degradation of methylene blue in aqueous solution, and high photocatalytic activity was observed.     

Study on dynamic interfacial tension of 3-dodecyloxy-2-hydroxypropyl trimethyl ammonium bromide at liquid/liquid interface

Dynamic interfacial tension between aqueous solutions of 3-dodecyloxy-2-hydroxypropyl trimethyl ammonium bromide (R₁₂HTAB) and n-hexane were measured using the spinning drop method. The effects of the R₁₂HTAB concentration (the concentration below the CMC) and temperature on the dynamic interfacial tension have been investigated; the reason of the change of dynamic interfacial tension with time has been discussed. The effective diffusion coefficient, D_a, and the adsorption barrier, _a, have been obtained from the experimental data using the extended Word–Tordai equation. The results show that the dynamic interfacial tension becomes smaller while _a becomes higher with increasing R₁₂HTAB concentration in the bulk aqueous phase. D_a decreases from 5.56 × 10⁻¹² m⁻² s⁻¹ to 0.87 × 10⁻¹² m⁻² s⁻¹ while _a increases from 5.41 kJ mol⁻¹ to 7.74 kJ mol⁻¹ with the increase of concentration in the bulk solution of R₁₂HTAB from 0.5 × 10⁻³ mol dm⁻³ to 4 × 10⁻³ mol dm⁻³. Change of temperature affects the adsorption rate through altering D_a and _a. The value of D_a increases from 5.56 × 10⁻¹² m⁻² s⁻¹ to 13.98 × 10⁻¹² m⁻² s⁻¹ while that of _a decreases from 5.41 kJ mol⁻¹ to 5.07 kJ mol⁻¹ with temperature ascending from 303 K to 323 K. The adsorption of surfactant from the bulk phase into the interface follows a mixed diffusion–activation mechanism, which has been discussed in the light of interaction between surfactant molecules, diffusion and thermo-motion of molecules.