(621d) Kinetic Monte Carlo Simulation of Branch-Length Distribution in the Seeded, Semibatch Emulsion Polymerization of Butyl Acrylate
AIChE Annual Meeting
Thursday, November 12, 2009 - 4:30pm to 4:55pm
For monomers which readily undergo radical chain transfer to polymer, such as vinyl acetate and butyl acrylate, the final properties of a latex vary with the branching structure of the polymer. As shown by Plessis, et al., the level of branching and molecular weight distribution affect the adhesive properties of a poly(butyl acrylate-styrene) latex . Former, et al. observed that the rheological properties of a poly(butyl acrylate) latex vary with the level of branching . In butyl acrylate polymerizations, radicals are known to chain transfer via both intermolecular and intramolecular, or ?backbiting,? reactions . In backbiting, a radical transfers to another mer in its own molecule, usually a small number of mers from the radical. Arzamendi and Leiza performed population-balance kinetic Monte Carlo simulations of a seeded, semibatch emulsion polymerization of butyl acrylate, and made the assumption that all backbiting reactions result in short-chain branches, while all intermolecular chain transfer reactions result in long-chain branches . Short-chain branches reduce viscosity by increasing the spacing between molecules, while long chain branches increase viscosity by increasing the number of entanglements . We have performed lattice KMC simulations of the backbiting reaction, incorporating diffusion, which give a distribution of the backbiting distance, and the resulting branch lengths. By incorporating this backbiting-distance distribution into a population-balance KMC simulation of the seeded, semibatch emulsion polymerization of butyl acrylate, we obtain a distribution of branch lengths, allowing us to more accurately predict the variation of particle viscosity with the level of branching.
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