Thermal and Photo-Induced Reactions of Radicals

The spectral change during this progressive warming to room temperature is shown in Fig. 12 for the sample irradiated and photobleached at 77 K. Elimination of the anion radical by photobleaching with visible light makes the analysis of the spectral shape easy. Then the observed spectral change indicates  

No difference in the spectral features was observed above 180 K between the samples with and without the elimination of the anion radical by photobleaching prior to warming. 

The formation of ethyl radical from the similar photobleaching experiment for poly(ethyl methacrylate) definitely indicates that the methyl radical is not from the elimination of the a-methyl group, as once postulated [38], but is from the splitting of methyl group in the ester side chain. 

Further irradiation with UV light causes the formation of new radical species with a broad singlet spectrum at the expenses of the triplet spectrum due 

The similar photo-induced radical conversion has been confirmed also for methyl pivalate, C(CH3)3COOCH3, as a model compound of PMMA [43]. 

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