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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 489-494 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ESR study of the radicals formed in mechanochemical polymerization of acrylamide (AAM) was undertaken. The nature of the radical formation was compared with the mechano-radical formation produced by mechanical fracture of polyacrylamide (PAAM). The structure of radicals formed were all identified to be an end-chain radical, equivalent to a polymer-chain propagating radical. The computer simulation disclosed that the observed spectra of the propagating radical can be approximated essentially by two kinds of component spectra, a large amount of triplet, and a small amount of quarter (a triplet of doublets). Thus, the existence of two major conformers in a single end-chain radical has been proposed. The ESR kinetics of the radical formation were further studied and its correlation with the nature of polymerization (the changes in molecular weight and polymer conversion) was discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 379-387 
    ISSN: 0887-624X
    Keywords: plasma-induced radicals ; electron spin resonance (ESR) ; crosslinked methacrylic polymer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plasma-induced radicals of several crosslinked methacrylic polymers such as poly(ethyleneglycol dimethacrylate) (PEDMA), poly(2-hydroxyethylmethacrylate) (PHEMA) and polymethacrylamide (PMAAm) were studied by electron spin resonance (ESR). The observed ESR spectra did not exhibit a drastic difference in the spectral feature caused by the effect of crosslinking. All the spectral features can be represented by “nine-line spectra” as a major spectral component similar to those of linear methacrylic polymers such as polymethacrylic acid (PMAA). A pronounced effect of crosslinking, however, has emerged on the specific formation in the radical structure and the stability of radicals formed, especially in PEDMA. The formation of fewer kinds of radical in PEDMA is apparently caused by the high degree of crosslinking which leads to a suppression of the occurrence of depolymerization on plasma irradiation.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1-7 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plasma-induced polystyrene radicals were first studied by electron spin resonance (ESR). The room temperature ESR spectrum was compared with those obtained by γ-irradiation, UV-irradiation, and mechanical fracture. It was found that even less than a few seconds of plasma-irradiation gave rise to a large amount of polystyrene radicals and the ESR spectrum consisted of two types of spectra, a triplet and a single broad line. The spectral feature of the triplet was nearly identical with that of γ-irradiated polystyrene. Thus, it was assigned to the structure of a cyclohexadienyl-type radical formed by a nearly random addition of a hydrogen atom to the aromatic ring. The single broad line, thought to be an outline of multicomponent spectrum, was assigned to an immobilized dangling-bond sites at the plasma-induced crosslinked portion of the polystyrene surface.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 97-103 
    ISSN: 0887-6266
    Keywords: radical formation in methacrylic polymers under anaerobic milling ; methacrylic vinyl polymers, formation and oxidation of mechanoradicals in air ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The formation of mechanoradicals under anaerobic conditions and their reactivity with oxygen at room temperature is described for several methacrylic vinyl polymers. Observed electron spin resonance (ESR) spectra of the mechanoradicals formed were all essentially identical and are clearly assigned to a respective endchain radical. The ESR kinetics of the mechanoradical formation of polymethylmethacrylate (PMMA) and polymethacrylamide (PMAAm) exhibit an interesting contrast; the progressive changes in the radical concentration in PMMA as a function of duration of milling gradually decrease after reaching a maximum value, while those of PMAAm show a parabolic increase. This discrepancy has been ascribed to mechanoradicals of PMAAm that are strongly stabilized by intermolecular and intramolecular doubly hydrogen-bonded networks among the amide groups. Such interactions also are to lower the reactivity of the mechanoradicals with oxygen. Thus, the mechanoradicals of both PMAAm and PMAA do not give a single peroxy radical, but rather a mixture of the mechanoradical and peroxy radical even after exposure to air, while the mechanoradicals of other polymers are rapidly converted to the corresponding peroxy radicals. Such a difference was observed in experiments on the mechanical fracture of such polymers under aerobic conditions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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