PHOTOOXIDATION OF POLYMERS - COMPARISON WITH LOW-MOLECULAR WEIGHT COMPOUNDS

The photo-oxidation of polymers involves different steps in which their reactivity is different from that of low molecular weight com-pounds. This is mainly due to the close vicinity of reactive groups in polymers and to the rigidity of the matrix. As a consequence, transfer of energy has a major role in the initiation of the photo-oxidation of most polymers on exposure to sunlight. It results in the sensitized decomposition of neighbouring hydroperoxide groups which, however, produce free radicals and thus initiate the oxidation less efficiently than model compounds in fluid solution. Scission of the polymer backbone, responsible for the alteration of the physical and mechanical properties, involves the decomposition of isolated hydroperoxide groups by two different mechanisms the relative importance of which changes with temperature. © IUPAC