The effect of aromatic solvents on the absolute rate coefficients in the polymerization of methyl methacrylate at 25°C

The Polymerization of methyl methacrylate in a variety of aromatic solvents has been studied at 25°C, using light of wavelength 3650 Å and azo‐bis‐isobutyronitrile as photosensitizer. Under the conditions of our experiments the rates of polymerization for the solvents used increase in the order benzene < fluorobenzene < chlorobenzene < anisole < bromobenzene < benzonitrile. Determinations of the absolute rate coefficients for propagation and termination in the different solvents show that the dependence of the rate of polymerization on the nature of the solvent arises in part from the viscosity dependence of the termination coefficient and in part from a dependence of the propagation coefficient on the nature of the solvent. The rate of initiation does not appear to be influenced by the nature of the solvent.