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PHOTOCHEMISTRY OF cis ‐POLYISOPRENE AND ITS SINGLET OXYGEN ADDUCT
Author(s) -
Ng Howard C.,
Guillet James E.
Publication year - 1978
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1978.tb06971.x
Subject(s) - singlet oxygen , photochemistry , peroxide , chemistry , cyclohexane , polymer , allylic rearrangement , bond cleavage , photodegradation , double bond , decomposition , singlet state , adduct , kinetics , oxygen , photodissociation , reaction mechanism , polymer chemistry , excited state , catalysis , organic chemistry , photocatalysis , physics , quantum mechanics , nuclear physics
— Reaction of singlet oxygen ( 1 Δ g , 1 O 2 ) with cis ‐polyisoprene yields an allylic hydroperoxide with an olefinic double bond shifted in the polymer chain. The photochemical decomposition of the resultant hydro‐peroxide and the subsequent polymer chain scission kinetics have been studied in the absence of oxygen. Quantum yields of hydroperoxide decomposition range from 3.1 to 8.4 in cyclohexane, depending on the initial amount of hydroperoxide in the polymer. On the other hand, the quantum yields for polymer chain scission are low, and vary with the frequency of the incident light. The ratio for number of polymer scissions per number of hydroperoxy groups decomposed is of the order of 10 ‐2 . The polymer chain degradation is sensitized by the addition of ketones. Based on these data, a reaction mechanism for the overall photodegradation of the cis ‐polyisoprene initiated by singlet oxygen is proposed.