Bulk Free Radical Polymerization of Methyl Methacrylate and Vinyl Acetate: A Comparative Study

摘要

The model and methodology for estimating diffusion-controlled rate coefficients for the methyl methacrylate (MMA) polymerization system is extended to the vinyl acetate (VAc) case. Comparison of the kinetic behavior and termination rate coefficients (k(t)) of both monomers suggests that at low conversions the termination reaction is controlled by the chemical step, whereas at moderate and high conversions it is controlled by the diffusive step which in turn is determined by the segmental diffusion of the long radicals and not by the center of mass diffusion of short radicals. It is found that, for most of the conversion range, diffusion coefficient for VAc is lower than the one for MMA notwithstanding that k(tVAc) k(tMMA). An explanation of this apparent inconsistency on the base of the model results and in terms of segmental mobility is proposed.