Photodegradable Polymers Containing

Photodegradable Polymers Containing Starch The incorporation of a biodegradable natural filler such as starch in a nondegradable hydrocarbon polymer... 

D. R. Tyler, Mechanistic Aspects of the Photodegradation of Polymers Containing Metal-Metal Bonds Along Their Backbones, Chapter 4 in Macromolecules Containing Metals and Metal-Like Elements, Vol. 6, Transition Metal Containing Polymers, Eds., A. Abd-EI-Aziz, C. E. Carraher, C. H. Pittman, Jr., and M. Zeldin, pp. 77-109, Wiley, Hoboken, NJ, 2006. 

The polymers obtained by polymerization in the presehce of metal catalysts contain metal residues which cannot be removed so readily. It is also well known that transition metal ions act as sensitizers for the photooxidation of polyolefins (29). Kujirai et al. (30) found that photodegradation of polypropylene depends on the oxygen concentration and on the residues of the polymerization catalyst, and they concluded that oxidative photodegradation is sensitized by the initiator metal residues (ash). Very recently Scott (31) used transition metal ions as sensitizers to develop photodegradable polymers. 

To achieve an optimum efficiency of a copolymeric HAS in a particular polymer, the stabilizer has to have an optimum mol. wt. The principle of photodegradable polymers was exploited for a new class of degradable polymeric HAS. A rubbery terpolymer 194 containing 50-60% of 2,2,6,6-tetramethylpiperidyl acrylate moiety as a stabilizing component, n-octadecyl... 

The expression in Eq. (5), generally used in photobiology, implies the absorbance spectrum of the substrate to be highly correlated to the quantum yield spectrum. While Martin et al. [18] have suggested that the expression at Eq. (4) is perhap.s more appropriate for polymers containing photostabilizers and impurities, its practical superiority over the simpler form in Eq. (5) has not been demonstrated. It is feasible that in many polymer photodegradation processes the absorption factor merely scales the spectral quantum yield. The activation spectrum is then expressed as [18]... 

Mechanistic Aspects of the Photodegradation of Polymers Containing Metal-Metal Bonds Along Their Backbones... 

The Norrish I and II reactions may occur from the excited singlet (S ) or triplet (T ) states however the triplet state is much more favoured because of its longer lifetime (Table 1.1). Both Norrish reactions are responsible for the photodegradation of polymeric ketones (cf. section 3.2.1) and polymers containing main chain carbonyl groups. 

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