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  • Polymer and Materials Science  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Mechanism of radiation-induced degradation of poly(methyl methacrylate) as studied by ESR and electron spin echo methods (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1185-1196 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The role of radical species in the degradation of poly(methyl methacrylate) (PMMA) induced by γ-irradiation has been studied by means of electron spin resonance and electron spin echo spectroscopy. The major radical species generated initially at 77 K are assigned to main chain — CH — and side chain — COOCH2 radicals, and — COOCH3- anion radical. Only the — COOCH2 radical converts to the scission-type — CH2 — C(CH3)COOCH3 radical on warming the sample of 〉180 K. A part of the — CH — radical disappears on warming the sample of 〉265 K. It is concluded that the scission of PMMA main chain occurs by the intramolecular process from the — COOCH2 radical as the precursor state.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280519
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Efficiency of radiation-induced main-chain scission of poly (methyl methacrylate) depends on the irradiation temperature because of coexisting monomer (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2487-2492 
    Details
    ISSN: 0887-624X
    Keywords: PMMA ; radiolysis ; temperature effect ; degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Effect of irradiation temperature on the main-chain scission of poly (methyl methacrylate) (PMMA) caused by γ-irradiation was studied by means of gel permeation chromatography and ESR spectroscopy. Although no temperature dependency was observed on the scission efficiency for purified PMMA, the efficiency for crude or monomer-doped purified PMMA was decreased by decreasing the temperature below ca. 200 K. Above 200 K the efficiency was constant and did not depend on the purity of PMMA. ESR study of the irradiated PMMA revealed that the suppression of the scission below 200 K is induced by the addition of methyl methacrylate monomer to primary radical species, which otherwise cause the main-chain scission by warming the polymer above 200 K. The primary radical generated above 200 K immediately converts to the scission-type — CH2 — Ċ(CH3) COOCH3 radical through the β-scission of the polymer main chain, so that the efficiency of the scission does not depend on both the impurity and the irradiation temperature. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321310
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    Paper (German National Licenses)
    Fulltext
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