Stabilizer-free Dispersion Copolymerization of Styrene and Maleic Anhydride: Mathematical Model for Nucleation

This work proposes a new model for particle nucleation, in addition to particle growth, in the process of stabilizer-free dispersion copolymerization of styrene and maleic anhydride in organic solvents. This paper provides the first contribution to the modeling and simulation of the nucleation step in this process. The model considers that (1) polymerization takes place in both the continuous phase and the polymer particles; (2) radicals in the continuous phase that exceed the size Jcrit precipitate and form aggregates; (3) the coagulation between aggregates forms new particles; (4) the radicals in the continuous phase can also enter into the polymer particles, reducing the nucleation rate; and (5) the termination step inside the particles is diffusion-controlled. The model is able to correctly predict the time evolution of the monomer conversion, particle number, and particle size and was successfully validated against data obtained experimentally and from the literature. Different from the existing models, the proposed model does not require previous information regarding the particle size or number to initialize the model. The radical entry parameter and the radical solubility are important parameters that affect the nucleation step.