Elastic modulus of the crystalline regions of polyimide derived from poly(amic acid)–biphtalic dianhydride and p-phenylene diamine

The elastic modulus E_l of the crystalline regions in the direction parallel to the chain axis was measured by X-ray diffraction for polyimide derived from polyamic acid (biphthalic dianhydride and p-phenylene diamine). These specimens were cured by two different routes: curing at 200 °C, and at 400 °C for 1 h, respectively (2STEPS), and curing from 80 °C to 400 °C stepwise (nine steps) for 1 h at each step (STEPWISE). The E_l values of 54–169 GPa were obtained for the STEPWISE specimen and 80–178 GPa for the 2STEPS specimen, depending on the meridional reflection employed for measurement of the E_l value. A linear relationship between the E_l value and the fiber identity period was obtained from each meridional diffraction, such that the E_l value increased with an increase in the fiber identity period. The E_l value of the fully extended structure was estimated to be 210 GPa. These are considered to be due to the coexistence of polymorphs with different skeletal structures. The crystalline regions of the 2STEPS specimen seems to consist of a more extended skeleton than those of the STEPWISE specimen. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3294–3301, 1999     

Reductive coupling of carbonyl compounds using lanthanum metal

We found that lanthanum metal was an excellent agent for the reduction of carbonyl compounds in the presence of a catalytic amount of iodine. When carbonyl compounds were treated with lanthanum metal in the presence of a catalytic amount of iodine, the reductive coupling of the carbonyl compounds proceeded efficiently to afford the corresponding vic‐diols in moderate to good yields. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:81–85, 2000     

Temperature dependence of the elastic modulus of crystalline regions of isotactic poly(4-methyl-1-pentene)

The elastic modulus E ₁ of crystalline regions of isotactic poly(4-methyl-1-pentene) (P4M1P) in the direction parallel to the chain axis and its temperature dependence were investigated by x-ray diffraction. E ₁ values for the (001) and (007) planes of P4M1P agreed well at 4.1 GPa at room temperature. This small E value could be attributed both to the contracted helical conformation (7/2 helix) and to a large cross-sectional area of P4M1P in the crystalline regions. Though the lattice distortion of the first kind increased and partial destruction of crystallites occurred with increasing stress, the stress-strain curve for the crystal lattice was linear up to 80 MPa. However, the E₁ value remained unchanged up to 150°C. The lattice spacing for the (007) plane increased monotonously with increasing temperature, with a thermal expansion coefficient of 0.9 × 10^?4 K^?1. These phenomena were in contrast with the temperature dependence of E ₁ values of various polymers previously reported, in which E ₁ decreased in the temperature region where the thermal expansion coefficient changed. It is considered for P4M1P that the axail thermal molecular mitions which cause the decrement of E₁ do not take place and that the deformation mechanism of the chain molecules remains unchnaged in the crystalline regions over the temperature and stress range studied.     

Pd(0)‐catalyzed polycondensation of methyl propargyl carbonate and bisphenols under stoichiometrically imbalanced conditions

We found that a novel Pd(0)‐catalyzed polycondensation of methyl propargyl carbonate ( 1 ) and bisphenol analogs 4 such as 4,4′‐dihydroxydiphenyl ether (4b ) proceeded successfully and gave polyethers 5 having exomethylene groups. The polycondensation was affected by the kind of bisphenol analogs used. The molar ratio of 1 and 4 also affected the polymerization behavior. Polyethers 5 with higher molecular weights were obtained by polymerization with 0.5 equiv of 4 toward 1 . The use of 1 equiv of 4 gave poor results. When 4,4′‐dihydroxybenzophenone ( 4d ) was employed as a nucleophile, benzenesulfonamide ( 13 ) was needed as an additive for obtaining the corresponding polyether with higher molecular weight. The Pd(0)‐catalyzed condensation of 1 and p‐hydroxyacetophenone was conducted as a model reaction. The desired compound and three by‐products were produced. Two of the by‐products were formed by reaction of 1 and methanol liberated from 1 . The other one appeared to be formed via hydrogenolysis. The formation of the by‐products suggested that some terminal reactions took place in the polycondensation of 1 and 4 . © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2250–2261, 2008     

Slippage of nonsuperfluid helium films

We measured the mechanical response of 3He and 4He films on an oscillating substrate using an ultrasonic technique. Up to the coverage at which the fluid state appears at absolute zero, a part of the nonsuperfluid 3He and 4He films underwent slipping relative to the substrate at low temperatures. From the temperature dependence of the slippage, it was found that a thermally activated process plays an important role in the frictional force of this system.     

The reaction of hydrogen atoms with 1-butanethiol and thiolane the role of chemically activated 1-butanethiol

The reaction of 1-butanethiol with hydrogen atoms has been studied at temperatures of 295° and 576° K under the pressure of 660 Pa, using a conventional discharge-flow apparatus. The reaction products (besides hydrogen sulfide and methane) under the low conversion range (～10%) consisted mainly of n-butane, 1-butene, and propylene-propane, with the relative yields of 70, 25, and 5% at 295° K and 25, 50, and 10% at 576°K. Analysis of kinetic equations by numerical integration indicates that the following initial steps are consistent with the experimental results: where the following expressions have been derived for k₁ and k₂: The subsequent reaction of the butylthio radical with hydrogen atoms leads to the chemically activated 1-butanethiol which either stabilizes to 1-butanethiol or decomposes to 1-butene and hydrogen sulfide, depending on the experimental conditions. A similar analysis of the data on the thiolane-H system has yielded the following rate parameters for the initial step to form the 4-mercapto-1-butyl radical: .     

Synthesis of a novel C-6 nigrogen-substituted carbapenem from 6-aminopenicillanic acid

Synthesis of optically active 6-phthalimidocarbapenems from 6-aminopenicillanic acid is described.     

Novel method for linking CdS nanoparticles at liquid-liquid interface

Liquid-liquid interface of water-hexane provides a unique reaction environment in which CdS nanoparticles capped with mercaptoethylamine could be linked together to form a homodimer with a divalent acid chloride, sebacoyl chloride. Prior to the reaction, mercaptoethylamine-capped CdS in aqueous solution was purified by dialysis and freeze-drying. The observation with a transmission electron microscope suggested the formation of a homodimer of CdS nanoparticles.     

Partial Protection of Carbohydrate Derivatives. Part 21. Lead(II) Nitrate Mediated Triisopropylsilyl Ether Formation; Preparation of 2′-Deoxy-3′-O-triisopropylsilylribonucleosides

Introduction of the triisopropylsilyl protecting group to the 3′-position of 5′-O-aroyl-2′-deoxyribonucleosides wa effectively performed by the use of triisopropylsilyl chlor ide in DMF in the presence of pyridine and lead(II) nitrate the latter was substituted in this reaction for silver nitr ate. Simple treatment of the resulting triisopropylsilyl ethers with sodium methoxide in THF gave 2′-deoxy-3′-O-tri-isopropylsilylribonucleosides in excellent yields.