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  • 1
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR signal assignments of the labdane diterpenoids andrographolide and 14-deoxyandrographolide, along with their acetates, and isodeoxyandrographolide have been made. This study indicates that the C-6 and C-11 resonance assignments of isovirescenol-B, made earlier, should be interchanged.
    Additional Material: 1 Tab.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 993-1000 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal expansivity of semicrystalline polymers is interpreted within the framework of the composite model which has already been found useful in describing mechanical and optical properties as well as the thermal conductivity of a large number of polymers. The model assumes the polymers to be an aggregate of units composed of crystalline and amorphous phases. The thermal expansivities of the unit are calculated in terms of those of the constituents. In the undrawn state the units are distributed randomly, and the isotropic thermal expansivity of the bulk results. The development of strong anisotropy in thermal expansivity on drawing is explained in terms of preferred orientation of the units. The orientational changes on drawing have been directly calculated from the birefringence versus draw ratio data. The results of these investigations indicate that the present model is quite successful in interpreting thermal expansivity data for poly(oxymethylene) and poly(propylene) over the entire draw ratio and temperature range.
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  • 3
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 signal assignments of the labdane diterpenoids phlogantholide-A, its diacetate and isophlogantholide-A are reported. The assignments of the 13C NMR signals of 14-deoxyandrographolide and its diacetate, made earlier, have now been confirmed by lanthanide shift studies on the former and also by 13C spectral studies on anhydroandrographolide diacetate and 14-deoxy-11,12-didehydroandrographolide diacetate.
    Additional Material: 1 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 181 (1980), S. 1629-1635 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Et2Zn in combination with POCl3 induces the cationic polymerization of isobutyl vinyl ether and N-vinyl carbazole at ambient temperature. The rate is directly proportional to [Et2Zn]. [POCl3] up to a mole ratio of unity of the components, and thereafter it decreases. At a fixed ratio of [Et2Zn]/[POCl3] the rate is second order in [Isobutyl vinyl ether]. Rate and [η] decrease in the presence of basic additives, pyridine, and water. Unlike the system Et3Al/POCl3, the present combination does not lead to any stereoregular poly(isobutyl vinyl ether) at ambient or lower temperatures. A cationic mechanism is proposed and an appropriate kinetic scheme is suggested.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 261-264 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It was found that the Py-SO2 complex (4-140 mmol·1-1) initiates the photopolymerization of methyl methacrylate (MMA) in bulk at 40°C, the initiator exponent, kp2/kt, and the monomer exponent being 0,30, 1,27·10-2 1·mol-1·s-1, and 1,00, respectively. The radical generation is followed by an in-situ initiator-monomer complexation reaction. The kinetics of the photopolymerization of MMA were also studied using the (Py-SO2)-complex (0,01-0,35 mol·1-1) in redox combination with benzoyl peroxide (BZ2O2) (2 - 110 mmol·1-1) as initiator in the presence of variable concentrations of pyridine (1 - 7 mol·1-1). The initiation depends on the concentrations of all the reactants in the system, and the reaction order with respect to either component of the redox pair is equal to 0,5 or reasonably less than 0,5, depending on whether or not the initiating component in question is present in the system in excess compared to its counterpart in the redox combination. Variable monomer exponents, largely dependent on [BZ2O2], characterize the redox photopolymerization process. The monomer exponent value, unity at [BZ2O2] = 0, progressively decreases with increasing [BZ2O2] (non-ideal kinetics). The rate enhancing effect of the solvent pyridine is more prominent at higher [BZ2O2]. The kinetic nonidealities in each case were further analyzed and interpreted in terms of (a) primary radical termination and (b) degradative initiator transfer. Relative effects of the variation of the level of dilution with pyridine were also analyzed.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 1023-1034 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The theoretical interpretation of the anisotropic elastic properties of polypropylene is given. It was found that none of the existing models provide a unified description of the mechanical and optical properties of ultradrawn polypropylene. The composite model proposed by the authors, which takes into account the change in orientation and crystallinity on drawing, was applied to investigate the elastic moduli data of polypropylene for a wide range of temperature (-40 to 110°C) and over the entire drawing ratio range. The relationship between θ and θ′, the angles made by the C-axis of the composite unit with drawing direction, was found to be adequately described by the relation tan θ = φ(n) tan θ′. It was further observed that φ(n) in the above relation obtained from birefringence data predicts the correct orientational changes on drawing for the temperature range -40 to 24°C. This makes the evaluation of mechanical properties possible without introducing any arbitrary parameter. However, it is noticed that a particular analytical form of φ(n) with two parameters is quite successful in interpreting the mechanical properties data over the entire temperature range. The abrupt changes of the parameters at certain temperatures seem to be correlated with the β-relaxation and glass transition temperature.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 13 (1954), S. 461-469 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The scattering of light by solutions of a well-fractionated sample of polymethyl methacrylate in acetone, methyl ethyl ketone, and benzene, have been measured using 4358 and 5461 A. wave lengths as incident radiations. The average molecular weights of the polymer from turbidity measurements and lengths determined from angular dissymmetries of scattered light are 571,000 and 760 A. in acetone, 38,400,000 and 715 A. in methyl ethyl ketone, and 408,000 and 375 A. in benzene. The abnormal molecular weight observed in methyl ethyl ketone solution may be ascribed to low μ - μ0 value of the medium. The greater molecular extension in ketone than in benzene solutions is explained in terms of the relative magnitudes of solute-solvent interaction. The depolarization ratios ρu, ρv and ρh have been measured and the decrease of ρv and ρh with increase in concentration of the polymer in ketonic solvents and little change under similar conditions in benzene, are discussed in the light of the “molecular field effect” of Gans.
    Additional Material: 3 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 27 (1958), S. 575-577 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 163 (1973), S. 37-43 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Substanzpolymerisation von N-Vinylcarbazol (NVC) wurde mit 3d-Metalloxid-Katalysatoren durchgeführt, und die folgende Reaktivitätsreihe für die untersuchten Oxide wurde vorgeschlagen: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm V}_{\rm 2} {\rm O}_{\rm 5} {\rm 〉 MnO}_{\rm 2} {\rm 〉 TiO}_{\rm 2} {\rm 〉 Cr}_{\rm 2} {\rm O}_{\rm 3} {\rm 〉 NiO 〉 ZnO 〉 Cu}_{\rm 2} {\rm O 〉 CuO 〉 Co}_{\rm 3} {\rm O}_{\rm 4} {\rm andCoO} $$\end{document} wobei die Oxide des Kupfers und Kobalts nicht wirksam sind. Einige kinetische Untersuchungen wurden mit dem System NVC/MnO2 ausgeführt. Auf Grund der Verzögerung der Polymerisationsgeschwindigkeit bei Gegenwart von Wasser oder Thiophen wurde ein kationischer Mechanismus für die Polymerisation vorgeschlagen. Die Wirkungslosigkeit der Kupfer- und Kobaltoxide als Katalysatoren wurde vorläufig mit der Annahme gedeutet, daß sie eher oxydierend wirken als durch π-Komplex-Bindung. Rühren übt keinen Einfluß auf die Polymerisationsgeschwindigkeit aus.
    Notes: The bulk polymerization of N-Vinylcarbazole (NVC) is carried out using some 3 d-metal oxides as catalysts and the following order of reactivity is suggested for the various metal oxides studied: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm V}_{\rm 2} {\rm O}_{\rm 5} {\rm 〉 MnO}_{\rm 2} {\rm 〉 TiO}_{\rm 2} {\rm 〉 Cr}_{\rm 2} {\rm O}_{\rm 3} {\rm 〉 NiO 〉 ZnO 〉 Cu}_{\rm 2} {\rm O 〉 CuO 〉 Co}_{\rm 3} {\rm O}_{\rm 4} {\rm andCoO} $$\end{document} the oxides of copper and cobalt being ineffective. Some kinetic studies are carried out with the NVC/MnO2 system. Endorsed by the observed retardation of the rate in the presence of water and thiophene a cationic mechanism is suggested for the polymerization. The incapability of the oxides of Cu and Co to act as good catalysts is tentatively explained by supposing that they act as oxidizing rather than π-complexing polymerization catalysts. Stirring does not show any influence on the rate of polymerization.
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