5 - Modeling of MEP

Abstract

Several microemulsion polymerization (MEP) models based on both thermodynamic and kinetic arguments appeared. A first thermodynamic partitioning Guo's model was developed to count the monomer concentration in particles during MEP of styrene. One of the earliest Guo's kinetic model developed for four-component microemulsions [water, emulsifier (SDS), coemulsifier (1-pentanol), and monomer (styrene)], assumed that the nucleation occurs in the microemulsion droplets. Nomura and Suzuki proposed a model for the polymerization of styrene in which monomer concentration inside the particles decays linearly with conversion, nucleation occurs in the micelles, all radicals enter the micelles, aqueous-phase termination and entry into polymer particles are negligible, chain propagation ends in particles due to transfer to monomer, the particle size and molecular weight do not depend on conversion or initiator concentration. Morgan et al. presented a rather simple model to describe the behavior of the polymerization of hexyl methacrylate, which was chosen to avoid vitreous effects due to its low glass-transition temperature. The simulation is capable of reproducing the kinetic behavior and particle size distribution, which are perfectly identical with the theoretical calculation. Previous model overestimates the colloidal and kinetic parameters and the polymerization rate at high conversions. A simple Monte Carlo simulation model for the kinetics of microemulsion polymerization is proposed in the Nie's model. The differential estimation consideration allowed the obtainment of the active particles evolution, whose dependence was not linear with time as opposed to previous works. These models describe adequately the bell-shaped active polymer particle and polymerization rate vs time curves by the new particles evolution approach.