Unexpected effect of the monomer concentration on the rate of a radical polymerization

Abstract

AbstractThe radical polymerization of vinyl monomers is usually initiated by physical and chemical means. After an increasing polymerization rate, Rp, at low monomer concentrations, some reactive systems show an unexpected minimum for Rp at high enough monomer concentrations. The radical polymerization of methyl methacrylate (MMA) initiated by the redox system D‐glucose–ceric ion at varying MMA concentration is discussed. The peculiar behaviour of Rp is explained by the presence of two circumstances: the initiation rate from D‐glucose radicals does not depend on MMA concentration when most of the D‐glucose radicals formed react by adding to monomer, and the radical chains initiated by D‐glucose radicals undergo mutual termination with a portion of the radical chains initiated by monomer radicals. Some information about the nature of the polymer end‐groups is reached from the mechanistic approach.