COMPARISON BETWEEN POLYMER DIFFUSION AND CHAIN RADICAL TERMINATION KINETICS - THE IMPORTANCE OF POLYDISPERSITY

The diffusion coefficient of labeled poly(methyl methacrylate) (PMMA) has been measured by forced Rayleigh scattering from solutions contain ing labeled polymer, matrix PMMA, and toluene. Several combinations of the labeled and matrix polymer molecular weights were used. The matri x polymer concentration was varied from 0 to 40% by weight. Under the assumption that the rate of chain termination is controlled by the dif fusion of the chain radicals, the diffusion data have been compared wi th available data for the rate coefficient of termination of PMMA radi cals measured over the same polymer concentration range. The compariso n shows that the distribution of chain radical molecular weight has a pronounced influence on the kinetics of termination.