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Mathematical Modeling of a Dispersive Suspension Polymerization

Carla Luciani1, Yunju Jung1, Joong Jin Han2, and Kyu Yong Choi2. (1) Chemical and Biomolecular Engineering, University of Maryland, Bldg 090, College Park, MD 20742, (2) Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, College Park, MD 20742

Porous particles exhibit a variety of applications. Recently, a novel synthetic method for producing porous polymer particles has been developed. It is based on the phase separation process that takes place inside monomer droplets along a suspension polymerization. In this paper, a mathematical model that describes a dispersive suspension polymerization of methyl methacrylate is presented, and the evolutions of conversion, phase volumes, and polymer molecular structure are predicted. The phase separation point and the distribution of species between phases are calculated through the Flory-Huggins theory. In each phase, the kinetic mechanism involves thermal and chemical initiation, propagation, chain transfer to the monomer, and termination reactions. Gel effect and volume contraction are also considered by the model. The global results are used as the input of another model for estimating the morphology of the polymer particles. This last model assumes that an intra-particle instantaneous local distribution of species is the main responsible for the morphology development. Due to this local distribution, a fraction of the polymer chains is produced homogeneously, yielding a dense structure; while the other fraction precipitates yielding a less dense structure. The proposed model requires to solve global and local mass balances, chemical potential balances, fluid-dynamic correlations, and population balances. It is adjusted and validated with experimental results.