Bipolar ions and σ-complexes in the ionic polymerization of nitrostyrenes☆

The polymerization of 2,4-dinitrostyrene and 2,4,6-trinitrostyrene under the action of alcoholates of alkaline metals and primary and tertiary aliphatic amines has been investigated. Four types of active particles in the initiation and propagation stages have been identified from analysis of experimental and calculated absorption spectra of the polymerizing systems and those of a number of model compouds; namely, nitrobenzyl anions, bipolar ions and Meisenheimer and Yanovskii σ-complexes. The complicated equilibria in which these particles and the initial reactants participate have been investigated. It has been shown that the anions and the bipolar ions are linked, during the course of the propagation reaction, at the aromatic ring both to monomer molecules and to internal links of the polymer. The solid-phase polymerization 2,4,6-trinitrostyrene under the action of diazobicyclooctane has been studied. The polymerization mechanism is discussed within the framework of concepts concerning the elementary act of the reaction.