Simultaneous application of two or more supported liquid-phase organometallic catalysts: heterogeneous multifunctional reaction systems

Using the form of supported liquid-phase catalysts, two or more homogeneous catalysts can simultaneously be used with retaining their own activities and taking the advantage of catalyst-product separation and catalyst recycling.     

Bildung von Fe3S4?FeS2 durch hydrothermale Reaktion

A mixture of Fe₃S₄ (greigite) and FeS₂ (pyrite) is formed at 200°C on hydrothermal treatment of freshly precipitated iron sulphide. Its electron diffraction diagramm was recorded, which corresponded to an incomplete solid solution of Fe₃S₄ and FeS₂. The surface and the interior of the spherical particles of the samples (size about 500 Å) consisted of Fe₃S₄ and FeS₂, respectively.     

Conductive characteristics of radical‐bearing polythiophenes using a microcomb‐shaped electrode

The electric conductivity of π‐conjugated and radical‐bearing polymers, i.e., polythiophenes bearing pendant galvinoxyl and phenoxyl radical groups, was measured using a microcomb‐shaped electrode. The electric conductivity was found to be enhanced by the radical content in the polymer. The infrared (IR) and Raman spectroscopies suggested a structural change from an aromatic form to a quinoid one in the polythiophene backbone by the phenoxyl radical generation. The effect of the pendant galvinoxyl radical's unpaired electron on the electric conductivity of the polythiophene was discussed by comparing the conductivity of a radical‐bearing polystyrene and a polythiophene mixed with low‐molecular radical molecules. Copyright © 2007 John Wiley & Sons, Ltd.     

A comparison of supercritical carbon dioxide and organic solvents for the intercalation of 4-phenylazoaniline into a pillared clay mineral

The intercalation of 4-phenylazoaniline (PAA) in supercritical carbon dioxide (SC-CO(2)) into montmorillonite (TMA-Mnt) pillared with tetramethylammonium ions at 313 K and 15 MPa was investigated. The adsorption rate and equilibrium PAA uptake were compared with those in n-hexane, CCl(4) and benzene solutions at 313 K. The XRD and N(2) adsorption/desorption analyses showed that TMA-Mnt after adsorption of PAA in SC-CO(2) had the same pore structure as after adsorption of PAA in normal solvents. SC-CO(2) was found to be a good medium for PAA adsorption owing to its having a relatively high adsorption rate and the highest adsorptivity at the same PAA concentration. The properties of PAA adsorption on TMA-Mnt could be well elucidated by the difference in solubility parameters between liquid and solid phases.     

Control of viscoelasticity using redox reaction

The viscoelasticity of a fluid was tuned with the Faradaic reaction of (11-ferrocenylundecyl)trimethylammonium bromide (FTMA), a "redox-switchable" surfactant. An aqueous solution of the reduced form of FTMA exhibited a remarkable viscoelasticity in the presence of sodium salicylate (NaSal) because of the formation of three-dimensional entanglement of wormlike micelles. Electrolytic oxidation of FTMA caused the viscosity of the system to dramatically decrease and the elasticity to disappear. This drastic decrease in viscoelasticity arose from the disruption of wormlike micelles. This novel electrorheological phenomenon is expected to be applicable to ink for inkjet printers, the electrochemically controlled release of substances entrapped in wormlike micelles of FTMA, and fluid flow rate control using electric signals.     

Diaminothiazoles and diaminothiophenes

Several 2,4-diaminothiazoles and 2,4-diaminothiophenes could be easily obtained by metallation using LDA from aminomethylthiomethylenecyanamides $\text{2}$ and aminomethylthiomethylenemalononitrile, respectively.     

Thermodynamically stable vesicle formation from glycolipid biosurfactant sponge phase

Thermodynamically stable vesicle (L(alpha1)) formation from glycolipid biosurfactant sponge phase (L(3)) and its mechanism were investigated using a "natural" biocompatible mannosyl-erythritol lipid-A (MEL-A)/L-alpha-dilauroylphosphatidylcholine (DLPC) mixture by varying the composition. The trapping efficiency for calcein and turbidity measurements clearly indicated the existence of three regions: while the trapping efficiencies of the mixed MEL-A/DLPC assemblies at the compositions with X(DLPC)< or =0.1 or X(DLPC)> or =0.8 were almost zero, the mixed assemblies at the compositions with 0.1 or =0.8 were multilamellar vesicles (L(alpha)) with diameter from 2 to 10 microm. Meanwhile, dynamic light scattering (DLS) measurement revealed that the average size of the vesicles at the composition of X(DLPC)=0.3 was 633.2 nm, which is remarkably small compared to other compositions. Moreover, the mixed vesicle solution at the composition of X(DLPC)=0.3 was slightly bluish and turbid and kept its dispersion stability at 25 degrees C for more than 3 months, indicating the formation of a thermodynamically stable vesicle (L(alpha1)). These results exhibited the formation of a thermodynamically stable vesicle (L(alpha1)) with a high dispersibility from the MEL-A/DLPC mixture. The asymmetric distribution of MEL-A and DLPC in the two vesicle monolayers caused by the difference in geometrical structures is very likely to have changed their self-assembled structure from a sponge phase (L(3)) to a thermodynamically stable vesicle (L(alpha1)).     

Determination of arsenic at the picogram level by atomic absorption spectrometry with miniaturized suction-flow hydride generation

A continuous-flow hydride generator is modified and miniaturized for the determination of picogram amounts of arsenic by atomic absorption spectrometry. A 300-μl sample is dropped into a teflon cup and pumped into an alkaline sodium tetrahydroborate stream, which is acidified in a reaction coil. The evolved hydride is swept with argon through a phase separator into an electrically-heated quartz absorption cell and the absorbance is recorded. To eliminate differences in sensitivity between arsenic(III) and arsenic(V) without prereduction by potassium iodide, it is important that arsenic(V) be mixed with tetrahydroborate prior to mixing with hydrochloric acid. The method has a detection limit of 0.08 ng As ml^?1 (24 pg) and the calibrations is linear up to 50 ng As ml^?1. The relative standard deviation for 10 replicate measurements is 5.4% for 0.5 ng As ml^?1. The addition of potassium iodide and hydroxylamine is confirmed to be effective in minimizing some interferences. The sampling rate is 90 h^?1. Results for NBS biological and steel reference materials demonstrate applicability of the technique.     

A [2]rotaxane capped by a cyclodextrin and a guest: formation of supramolecular [2]rotaxane polymer

A [2]rotaxane capped by a beta-cyclodextrin and a 2,4,6-trinitrophenyl group has been prepared by dissolving 6-aminocinnamoyl beta-cyclodextrin in water with 1-adamantane carboxylic acid and complexation with alpha-cyclodextrin followed by the reaction with 2,4,6-trinitrobenzene sulfonic acid sodium salt. The [2]rotaxane has been found to form supramolecular polymers by host-guest interactions.     

Kinetic approach to radiation-induced grafting in the polyethylene–styrene system. II

The investigation method reported in the previous paper was applied to four reaction methods: preirradiation method with reaction in liquid monomer, preirradiation method with reaction in monomer vapor, simultaneous irradiation method in liquid, and simultaneous irradiation method in vapor. The increasing patterns and values of the degree of grafting experimentally obtained roughly agreed with those calculated by using the same rate constants. At high monomer concentration, the rate of grafting was small; at low monomer concentration, the rate of grafting was large. Strictly speaking, the data by simultaneous irradiation method were somewhat larger than those by calculation. Two additional factors, as homopolymerization and the grafting from the radicals formed on the grafted polystyrene, were considered and discussed. The rate constants obtained were also discussed.