Title: Origin of dye bleaching and polymer degradation in the methylene blue-sensitized photo-oxygenation of polybutadiene
Abstract: Polymer chain scission and bleaching of the sensitizer are observed during the photo-oxygenation of cis-1,4-polybutadiene (PH) sensitized by several dyes in solution. The methylene blue (MB) sensitized photo-oxygenation of PH in benzene:methanol 9:1 occurs via a singlet oxygen mechanism. The decreases in MB concentration and molecular weight of PH exhibit an induction period followed by an increasing rate. It is shown that these two processes are consecutive to the formation of the hydroperoxy groups. Their possible origin is examined and discussed. It is concluded that both phenomena arise from an interaction of the polymeric hydroperoxy groups with the triplet state of the dye. The results are consistent with a sensitized photolysis of hydroperoxy groups which yield radical species leading to bleaching and chain scission with an efficiency about three orders of magnitude lower than that of photo-oxygenation. It is proposed that these processes may be significant in photodynamic action.
Publication Year: 1992
Publication Date: 1992-03-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 26
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