Modeling Semi-Batch Vinyl Acetate Polymerization Processes

Poly(vinyl acetate) (PVAc) is a polymer of high industrial importance. The final properties of PVAc and products thereof are strongly dependent on its microstructure, which, in turn, is determined by the specific polymerization conditions and processes used for its production. In silico modeling approaches based on kinetic Monte Carlo simulations are of high interest since they can enable the prediction of the microstructural characteristics of the resulting polymer chains, as long as the model considers the specific (and complex) polymerization and process conditions. In this study, a robust and versatile kinetic Monte Carlo model was developed, allowing for the treatment of semi-batch radical polymerizations of vinyl acetate in methanol under reflux conditions. The kinetic model comprises a full kinetic scheme for the initiation, termination, propagation, and transfer reactions. The majority of the required rate coefficients for the elementary reactions is available from the literature. With respect to the diffusion-controlled termination reaction, the composite model, which represents the chain length dependence (CLD) of kt, has been extended to account for the polymer content in the system. The robustness of the kinetic model is demonstrated by the very good agreement between the experimental and calculated molar mass distributions of PVAc obtained at different reaction times and regardless of the feeding profiles used.