Effect of matrix rigidity on the reactions of aromatic nitrenes in polymers

Abstract

The main products of the photolysis of aromatic azides in matrices of polystyrene, paraffin wax, polyisoprene and some other polymers are primary and secondary amines. The yield of secondary amine in the matrix depends strongly on the rigidity of the polymeric system. Matrix rigidity affects also the reaction kinetics of the nitrene intermediate, lifetimes of photogenerated triplet nitrenes being up to three orders of magnitude longer in rigid matrices than in plasticized materials. From the results of flash photolysis experiments, it is concluded that in the rigid matrix the rate of interaction between a reactive species and the polymer is not controlled by the chemical reactivities of reactant and substrate, but by a steric rearrangement of the polymer chain in the vicinity of the reactive site.