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  • 1
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 Fourier-transform spectra (67.88 MHz) of 1,2-polybutadienes (PBDs) (I-IV) were obtained. The triad and pentad intensities were calculated for the olefinic methylene carbon (C-1). Bernoullian and first-order Markov-chain propagation statistics were tested to fit the experimental data. The pentad placements for the olefinic methine carbon (C-2) were also assigned using the data calculated for the C-1 carbon. Fine-structure splitting due to placements higher than pentads was observed for both C-1 and C-2 carbons in PBD samples III and IV.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 2133-2144 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Styrene was found to yield saturated and unsaturated linear oligomers in the presence of a surface-supported catalyst, molybdenum oxide on silica-alumina. The reaction rates, the structure, and the molecular weight distribution of the products were found to be controlled by the choice of the solvent. Higher-molecular-weight fractions were favored in isooctane, whereas low-molecular-weight oligomers were preferred in dioxane. The reaction followed first-order kinetics with respect to the monomer. End-group analysis suggests a probable cationic mechanism. Approximate transfer constants KtrKp were deduced from product distribution data. The behavior of the surface-supported catalyst was compared with other cationic catalyst systems.
    Additional Material: 7 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 3197-3208 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal decomposition of cis-1,4-, trans-1,4-, and 1,2-polybutadienes (PBD) in the temperature range 450-900°C was investigated by pyrolysis gas chromatography (PGC). The cis- and trans-PBDs have closely similar product distribution and can be readily distinguished at lower temperatures of pyrolysis from the 1,2-PBD by the low amount of vinyl cyclohexene (VCH) produced by the 1,2 species. The amount of butadiene (BD) produced by 1,2-PBD varies with the tacticity of the polymer; the greater syndiotactic yields a lesser amount of BD. A method of determining the 1,4 and the 1,2 contents of PBD based on the ratios of peak heights of ethylene (C2) to VCH, propylene (C3) to VCH, and BD to VCH is presented. The advantages of this method are discussed. The nature and composition of the products of pyrolysis in the temperature range 540-900°C are presented and the mechanism of degradation at these elevated temperatures is explained.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 1743-1756 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several polyamides of p-phenylenedioxydiacetic acid (PDDA) were synthesized by the low-temperature solution polycondensation techniques. Six different diamines were condensed independently with p-phenylenedioxydiacetyl chloride (PDC) in a mixture of N-methyl pyrolidone (NMP) and hexamethyl phosphoramide (HMPA). The polymers were obtained in 80-95% yield and possessed inherent viscosities in the range 0.32-0.81 dL/g. The polymers were characterized by infrared (IR) and H1-NMR spectra. The solubility, density, crystallinity, and thermal stability of the polyamides were also determined. A model diamide (MDA-1) was also synthesized from aniline and PDC to confirm the formation of polyamides from diamines.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 373-376 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 2317-2327 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A process is described for the conversion of methylricinoleate, the major castor oil, fatty acid ester, directly into esters of dimer and oligomer acids by using molybdenum oxide on a silica-alumina catalyst. The dehydration of the methylricinoleate into a corresponding mixture of conjugated and nonconjugated olefins and the oligomerization reaction took place side by side in a continuous column, fixed-bed reactor. The products are characterized by IR, 1H NMR, and MS. The fragmentation pattern in the mass spectrum of the dimeric species distilled from the mixture reveals that the product contains cyclic and acyclic isomeric structures. The mechanism of dimerization and oligomerization reactions to transition metal complexes and transition metal oxide catalyst systems is reviewed briefly and the possibility of a common mechanism for all similar systems is suggested. A general mechanism for oligomerization reactions to similar catalysts is proposed and the products of the present reaction are explained on the basis of the proposed mechanism.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 3805-3814 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A process is described for the oligomerization of methyl ester of dehydrated castor oil fatty acid over molybdenum oxide on silica-alumina catalyst. The process is compared with thermal oligomerization. The nature of the reaction in both the processes are shown to be the same from the structural elucidation of the product despite the variation in product composition. The percentage of dimer in the product in both the processes is observed to attain an equilibrium value at around 270°C. The catalytic process is shown to follow a second-order kinetics with respect to the monomer, whereas the thermal reaction follows a first-order kinetics. The kinetic scheme derived for the catalytic process is shown to be consistent with the steps of the general mechanism proposed for oligomerization reactions over transition metal catalysts [V. G. Kumar, S. Venkatachalam, and K.V.C. Rao, J. Poly. Sci. Polym. Chem. Ed., 22, 3850 (1984)].
    Additional Material: 6 Ill.
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