Nitroxide Mediated Radical Emulsion Polymerization: Mathematical Modeling

Several mathematical models for nitroxide mediated polymerization (NMP) in miniemulsion have been reported, but virtually none for nitroxide mediated polymerization (NMP) in true emulsion polymerization; in part this is due to the scarcity of processes for performing NMP in this type of aqueous dispersions. Our group has recently developed a robust NMP emulsion semibatch process which is applicable to a variety of monomers and nitroxides. In this paper, the progress made in our group in the development of mathematical models aimed at explaining the experimental effects observed in the NMP emulsion process is presented. The modeling approach is based on population balances that describe the number of particles having a specific number of active radicals and a given concentration or number of nitroxide radicals. The partitioning of the nitroxide radical and its corresponding alkoxyamines between the organic and aqueous phases is included in the model. The approach and assumptions chosen are compared with those used in other models for NMP in aqueous dispersions. The model is used as a tool to understand the quantitative effects of the main variables on the process outputs; it can also be used for scaling-up purposes. Preliminary simulation results are presented and discussed.