Kinetics of free‐radical polymerisation at high viscosities

Methyl methacrylate und styrene were polymerised by a free‐radical process in solutions which contained dissolved polymer. The molecular weights of the dissolved polymer and the concentration of the radical generator 2,2'‐azoisobutyronitrile were varied. Rate data were compatible with a reaction scheme in which the mobility of some growing radicals was influenced by the solution viscosity. Correlations between radical mobility and viscosity were more consistent with the experimental results than correlations between radical mobility and volume fraction of dissolved polymer. The possibility of primary radical termination is examined and a means of clarifying the chain termination process is suggested.