Large-scale synthesis of perpendicularly aligned helical carbon nanotubes

Large-scale perpendicularly aligned helical carbon nanotube arrays were prepared by co-pyrolysis of Fe(CO)5 and pyridine onto the pristine quartz glass plates in a tube furnace at 900-1100 degrees C under a mixture flow of Ar and H2. The resultant aligned helical carbon nanotubes could not only facilitate the structure-property characterization for helical carbon nanotubes but also allow them to be effectively incorporated into devices for practical applications.     

Complexation-induced conformational regulation of ferrocene-dipeptide conjugates to nucleate γ-turn-like structure

The complexation of the ferrocene-dipeptide conjugate bearing one dipeptide chain of heterochiral sequence (-l-Ala-d-Pro-NHPy) with PdCl₂(MeCN)₂ was demonstrated to afford the 2:1 trans palladium complex, which is present in the pseudo-helical conformation and γ-turn-like structure in the crystal structure through complexation and intramolecular hydrogen bonding. Furthermore, the left-handed pseudo-helical molecular arrangement was formed through a network of intermolecular hydrogen bonds.     

A novel insertion reaction of epoxy compounds into phenyl ester linkages in polymer chains

The insertion reaction of various epoxy compounds such as phenyl glycidyl ether (PGE), methyl glycidyl ether, butyl glycidyl ether (BGE), and styrene oxide into the phenyl ester linkage in the polymer chain was investigated using quaternary ammonium salts as catalysts in diglyme, anisole, sulfolane, o-dichlorobenzene, or DMSO at 100–150°C. The reaction of PGE with poly[4-(4-nitrobenzoyloxy)styrene] (polymer 1a ) proceeded almost quantitatively to give the corresponding polymer using tetrabutylammonium bromide (TBAB) as catalyst in diglyme at 100°C for 24 h. The reactions of BGE with poly(4-nitrophenyl methacrylate), and copolyarylate derived from 2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane and iso- and terephthaloyl chlorides also produced the corresponding polymers with 86 and 89 mol% new structural units, respectively, using TBAB in sulfolane at 150°C for 24 h. Furthermore, it was found that the degree of insertion of the epoxy compound into the ester linkage in the polymer chain was affected by the kind of epoxy compound, reaction solvent, catalyst concentration, substituent group on the phenyl ester, and structure of the polymer. Chiral polymers were also synthesized with high degrees of insertion by the reaction of chiral epoxides such as (R)-1,2-epoxyhexane, (R)-1,2-epoxyheptane, and (R)-1,2-epoxydecane with polymer 1a and poly(2,4-dichlorophenyl methacrylate) using TBAB in diglyme at 120°C for 24 h.     

Cationic graft copolymerization of styrene onto natural rubber

The polymerization of styrene was carried out in a cyclohexane solution of natural rubber with stannic chloride. It was found that the grafting copolymerizations of styrene took place as well as the cyclization of rubber. The rate of polymerization of styrene was proportional to the second power of the concentration of styrene and to the concentrations of stannic chloride and natural rubber, respectively. The overall activation energy was about 6 kcal./mole. The percentage grafting increased with increasing concentration of rubber. On the other hand, the grafting efficiency showed the reverse tendency. The percentage grafting could be increased to 150% by the addition of nitrobenzene, a polar solvent.     

Why not use point charge models for the determination of bond angles?

Bond angles of several free radicals have been estimated using the point charge model together with ESR data and compared with those derived by Coulson's equation and the INDO method. The model is found to work well in predicting bond angles for most radicals just like the INDO method. Some relationships between the model and the INDO method are discussed.     

Chirality-organized ferrocene receptor bearing podand dipeptide chains (-L-Ala-L-Pro-NHPyMe) for the selective recognition of dicarboxylic acids

[structure: see text] The ferrocene receptor bearing the podand dipeptide chains (-l-Ala-l-Pro-NHPyMe) was found to provide a chirality-organized binding site through two intramolecular interchain hydrogen bonds between CO (Ala) and NH (another Ala) of each podand dipeptide chain. The size-selective and chiral recognition of dicarboxylic acids was achieved by multipoint hydrogen bonds of the binding site.     

Determination of very volatile organic compounds in environmental water by injection of a large amount of headspace gas into a gas chromatograph

An injection method for a large amount of headspace gas which enables determination of trace amounts of very volatile organic compounds (VVOCs), dichlorodifluoromethane, chloromethane, vinyl chloride, bromomethane, chloroethane and trichlorofluoromethane in all kinds of environmental water was developed. A gas phase equilibrated with the water phase in a vial was purged with helium for a short time. The VVOCs were then introduced into a trapping tube packed with Tenax TA, which had been cooled using carbon dioxide. After trapping, the VVOCs were thermally desorbed and put into a GC–MS system for subsequent analysis. This method is applicable to various types of samples.     

Effect of separators on the self-discharge reaction in nickel-metal hydride batteries

The effects of separators on the self-discharge behavior and the suppression of self-discharge by a sulfonated polyolefin separator were investigated with test cells. The experimental results indicate that a sulfonated polyolefin separator effectively suppresses the self-discharge reaction in nickel-metal hydride batteries. It is also found that a sulfonated polyolefin sheet does not necessarily need to be sandwiched by positive and negative electrodes to act as a separator; it can be placed anywhere within a cell to suppress the self-discharge reaction. The self-discharge reaction is considered to be suppressed by trapping redox shuttle substances, especially nitrogen-containing compounds, by the separator.     

The decomposition of potassium persulphate used as initiator in emulsion polymerization

The decomposition rate of potassium persulphate in various aqueous solutions was measured by isotachophoresis using pure water, sodium dodecyl sulphate (SDS) solution, emulsifier-free polystyrene emulsion, SDS solution containing acrylamide monomer or an SDS-containing emulsion polymerization system for styrene. “Free” SDS molecules in the monomolecular dispersed state were found to increase markedly the decomposition rate, whereas those which formed micelles and became adsorbed onto polystyrene particles did not increase it. The acceleration phenomenon in the former case disappeared in the presence of a small amount of monomer.