PHOTORADICAL AGING OF POLYMERS

New data referring to quantum efficiency of electronically excited mac roradicals and radical anion reactions in various carbon- and heteroch ain polymers at temperatures below their glass transition or melting p oints are presented and discussed. The data on the mechanism of the ph otochemical reactions of peroxy radicals, the effect of various factor s (photon energy, free volume, degree of crystallinity) on the directi on and efficiency of reactions of electronically excited macroradicals are considered. The important role of photochemical chain reactions i n photoageing is demonstrated. It is found that by varying photon ener gy, temperature, photolysis time and by taking advantage of the compet ition between thermal and photochemical reactions, it is possible to c hange the functional composition and molecular mass distribution of po lymers in the desired direction.