Kinetic and structural EPR studies of radical polymerization. Monomer, dimer, trimer and mid-chain radicals formed via the initiation of polymerization of acrylic acid and related compounds with electrophilic radicals (˙OH, SO4–˙ and Cl2–˙)

Abstract

A continuous-flow system has been used in conjunction with EPR spectroscopy to study the initial stages of polymerization of acrylic acid and methacrylic acid in aqueous solution at pH 2 and 9, brought about with inorganic radicals (e.g.˙OH) formed from metal–peroxide redox couples. Structural characteristics of monomer adduct-radicals, as well as corresponding dimers and trimers, are reported, together with evidence for rapid intramolecular hydrogen-abstraction of the appropriate tetramer to give a mid-chain radical. Computer-based simulation of steady-state concentrations leads to estimates of rate constants for initiation, propagation and termination reactions under these conditions.