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  • Chemistry  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Inclusion polymerization in perhydrotriphenylene studied by ESR spectroscopy: Growing chain structure and conformation of methylsubstituted polybutadienes (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 815-825 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Inclusion polymerization of diene monomers promoted by γ rays and performed in perhydrotriphenylene was studied by ESR techniques. During polymerization of butadiene, 1,3-pentadiene, isoprene, 2,3-dimethylbutadiene, 2-methylpentadiene, and 2,4-hexadiene, spectra attributable to allyl-type radicals were collected. It was demonstrated they actually represent the propagating radicals and they do not vary over a long period of time. They are not temperature dependent in the range -150°/ +60°C, apart from the radical of polybutadiene, suggesting that the included methyl-substituted polybutadienes are conformationally fixed. When the two opposite insertions of monomers 1,4 and 4,1 are distinguishable, the radicals bearing the higher number of methyl groups at the ends of allyl system prevail.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080240501
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  • 2
    Electronic Resource
    Electronic Resource
    Evidence of formation of radicals in the polystyrene thermodegradation (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 3865-3873 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of radicals in the thermal degradation of polystyrene (PS) in tubes sealed under vacuum has been evidenced by using ESR spectroscopy. The radicals were found to be stable for weeks at room temperature. The rate coefficients of the formation of radicals have been evaluated in the temperature range 350-420°C. The reaction kinetically followed has been related to the initiation step of the multi-step degradation process of PS. The activation energy of this reaction resulted 185 kJ/mol.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080271126
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  • 3
    Electronic Resource
    Electronic Resource
    Properties of surface-modified alumina catalysts of COS synthesis (1992)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 19 (1992), S. 529-532 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The surface electronic structure, the acid-base properties, the component adsorption and the catalytic activity of gamma alumina (CK-300, Ketjen) modified with surface sodium as a donor-type or iron as an acceptor-type additive have been investigated. Alumina was loaded with 0.1 and 1 wt.% Na and Fe. The catalytic O/S exchange of CO2 and CS2 to form COS was applied as a model reaction, for which the kinetic parameters have also been determined. In the case of unloaded alumina and samples loaded with 0.1 wt.% Na and 0.1 or 1.0% Fe no characteristic differences in the shape and position of the O 1s and Al 2p lines were observed. However, 1.0 wt.% Na loading resulted in a broadening of the O 1s and Al 2p lines towards lower binding energies. Sodium, even in 1% monolayer coverage, and other donor-type surface species, e.g. pre-adsorbed NH3 or pyridine, exhibited a readily detectable promoter effect which could be characterized by increased surface basicity, increased CO2 and CS2 adsorption and better catalytic performance. In contrast, on catalysts loaded with Fe an increase in surface acidic sites, a loss of basic sites, decreased component adsorption and lower catalytic activity were observed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740190198
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