DIFFUSION-CONTROLLED KINETICS FOR THE SOLUTION COPOLYMERIZATION OF 2-ETHYLHEXYL ACRYLATE WITH VINYL CHLOROACETATE IN A CSTR

The solution copolymerization of the comonomer pair 2‐ethylhexyl acrylate–vinyl chloroacetate (in ethyl acetate) has been studied in a continuous stirred tank reactor (CSTR). The initiator used in this study, 2,2′‐azobis‐2,4‐dimethyl valeronitrile was selected on the basis of its high decomposition rate constant. Measurements included the rate of copolymerization, the copolymer composition by infrared spectrophotometric analysis, the molecular weight distribution by gel permeation chromatography, and the viscosity of the reaction mixture by capillary viscometry. The reactivity ratios for the EHA–VCLAC pair were markedly different so that both propagating chains preferentially add EHA. Both the ϕ factor and the penultimate effect models were inadequate for describing the termination reaction. By defining an appropriate expression, based on physicochemical considerations, for the overall termination rate constant, it was possible to model the steady state rates by the diffusion model of Atherton and North. An attempt to model the transient behavior of the reactor by using the ϕ value as an adaptable correction factor was unsuccessful due to the rapid composition drift during approach to steady state. The measured conversions were lower than the model predictions for all feed ratios. Copyright © 1990 John Wiley & Sons, Inc.