MODELING OF TERMINATION IN INTERMEDIATE AND HIGH CONVERSION FREE-RADICAL POLYMERIZATIONS

A simple means of modeling termination in free radical polymerizations of a large number of monomers over a wide variety of intermediate and high conversion conditions is presented. It is shown that monomers ca n be divided into two classes according to the qualitative variation o f their termination rate coefficient (k(t)) with conversion (U). It is then suggested that it is profitable to represent k(t) data as k(t)/[ k(p) . (1 - U)]. Doing this reveals that over a wide range of temperat ures and of intermediate and high conversions, seemingly complex varia tions of k(t) with U can be described by a single parameter (C(RD)), t he value of which varies from monomer to monomer. Proceeding from the idea that the process of reaction-diffusion is the rate determining me chanism of termination, two easily implementable models for a priori p rediction of C(RD) are developed in parallel from already existing ide as. One of these models is shown to predict with remarkable accuracy a large variety of experimental C(RD) data. Slight modification of thes e predictions makes this model even more accurate, and therefore gives it great potential for modeling purposes.