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  • 11
    Electronic Resource
    Electronic Resource
    On the reactivity of cellulose free radicals in graft copolymerization reactions (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 1857-1869 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation and behavior of photo-and mechanoinduced free radicals in cellulose were studied by ESR spectroscopy and the capability of these free radicals to initiate graft copolymerization reactions was demonstrated. Although an 11-line ESR signal was detected from cellulose irradiated with ultraviolet (UV) light, a higher-intensity ESR signal with a five-line pattern was detected from a sample mechanically milled at 77 K. The decay of photoinduced free radicals when heated took place monotonously, whereas mechanoradicals exhibited an anomalous behavior with an increased signal intensity at 150 K before decaying at a higher temperature. Mechanoradicals have been found to react more efficiently and rapidly with oxygen and methyl methacrylate (MMA) than photoinduced free radicals. The peroxy mechanoradicals, however, were mobile and decayed more rapidly than the peroxy photoinduced radicals. Simultaneous graft copolymerizations of MMA to cellulose demonstrated that mechano-and photoinduced free radicals are capable of initiating grafting reactions, but a higher degree of grafting efficiency was obtained from cellulose treated mechanically.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180620
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  • 12
    Electronic Resource
    Electronic Resource
    Surface degradation of wood by ultraviolet light (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 2227-2241 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Wood is beautiful but sensitive to light. Because of the chromophoric system at its surface, ultraviolet light cannot penetrate it deeper than 80 μm. Surface characteristics of ultraviolettreated wood were analyzed by infrared and ultraviolet spectroscopy. Analyses of infrared spectra revealed that ultraviolet-treated wood is rich in carboxylic and carbonyl chromophoric groups and poor in aromatic functional groups. Ultraviolet spectral studies suggest that water-soluble low molecular weight fractions of degraded products from the wood surface are mainly derived from lignin. These degradation products contained carbonyl conjugated phenolic hydroxyl groups and had a weight-average molecular weight of about 900, confirmed by gel permeation chromatography.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.170220923
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  • 13
    Electronic Resource
    Electronic Resource
    Photooxidative degradation of cellulose: Reactions of the cellulosic free radicals with oxygenPresented at the 174th National Meeting of the American Chemical Society, August 28-September 2, 1977, Chicago, Illinois (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 441-454 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photooxidative degradation of cellulose resulted in decreases of degree of polymerization (DP) and α-cellulose content, concurrently producing chromophoric groups; namely, carbonyl, carboxyl, and hydroperoxide groups within the polymer. Electron spin resonance (ESR) studies revealed that cellulosic carbon free radicals readily reacted with oxygen molecules at 143-160 K to produce peroxy radicals, whereas cellulosic oxygen free radicals were inert toward oxygen molecules throughout the photooxygenation reactions. At 77 K it is feasible that only photoexcited oxygen molecules reacted with cellulosic carbon free radicals to produce peroxide radicals. These radicals were themselves stabilized at 273 K by abstraction of hydrogen atoms from cellulose to produce polymer hydroperoxides. Simultaneously, new radical sites, which exhibited three-line ESR spectra, were generated in cellulose.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170214
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    Paper (German National Licenses)
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