Interaction of excited molecules with macroradicals in the polymers under irradiation

The encounter complexes, which are formed in polystyrene (PS) and PS-based scintillators, combine the excimers and luminescent dopants with benzyl macroradicals known as efficient paramagnetic traps of excitation. The quenching of electronically excited states and dopants occurs via mechanisms other than energy transfer. The interaction of the radicals with excited molecules, which can be treated as a combination of migration and spin exchange in the encounter complex, results in an increase of the local concentration of triplet states in the radical neighborhood and the stabilizing of macroradicals primarily in the form of clusters. The radiolysis of these polymeric systems causes a space-correlated generation of macroradicals due to inhomogeneous structure of the polymers and specific interaction of the excited molecules with macroradicals. The efficiency of macroradicals as quenchers of the excited molecules depends not only on their concentration, but also on the character of their localizing in space. In other words, the efficiency will be lower with increasing the clusterization of macroradicals. The radiation resistance of the scintillators will be higher if macroradicals are stabilized in the form of clusters.