EVALUATION OF TERMINATION RATE BY SEGMENTAL AND TRANSLATIONAL DIFFUSIONS IN RADICAL POLYMERIZATIONS

A diffusion coefficient of a segment is proposed from the fact that the Mth segment from the end arrives at the place where the Nth segment is located by jumping (N–M) times. By using this and the translational diffusion coefficient derived previously, a termination-rate equation is formulated. After such an equation is applied to the diffusion-controlled model terminations, it is also applied to the polymerization rates in the polymerizations of styrene and methyl methacrylate (MMA) initiated by azo compounds, without any modification for reactions in terms of primary radicals. The mobility factor of a segment, which denotes the ratio of the segmental mobility to the mobility of a particle of the segment size, is estimated to be 0.24 for PMMA and 0.14 for polystyrene; these values would be independent of solvent properties. © 1979 The Society of Polymer Science, Japan.