| Abstract: | The rates of accumulation of oxygen-containing species in photooxidation have been determined for a series of polymers such as polystyrene, polyisoprene, and polybutadiene in a wide range of singlet oxygen stationary concentrations in the polymers. An increase in singlet oxygen (1O2) concentration was achieved by introducing a dye which is a 1O2 donor into a polymer and by irradiating a sample with an additional source of light absorbed by the dye only. To decrease 1O2 concentration, 1,2,5-trimethyl-4-hydroxyphenylpiperidine, which is a quencher of 1O2, was introduced into a sample. The 1O2 stationary concentration in an oxidized polymer was measured via singlet oxygen oxidation of 2,2,6,6-tetramethyl-4-oxypiperidine which leads to the formation of the corresponding nitroxyl radical. The photooxidation rate has been found to vary only slightly with 1O2 concentration, even when the concentration changes 10–25-fold. Thus, 1O2 does not participate appreciably in the process of polymer photooxidation. It may be due to the lowering of 1O2 reactivity toward unsaturated groups in the polymer matrix as compared with that in solution. |
