Kinetic Factors in Miniemulsion Polymerization

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Emulsion polymerization is used in industry for the production of polymer latexes for applications such as coatings, binders, adhesives, paints and foams. In this process, polymer particles are created in the presence of stabilizing emulsifiers with diffusion of monomer from large droplets (greater than approximately 10 microns in diameter) to the growing particles which are approximately 0.1 to 0.4 microns in diameter. An alternative to emulsion polymerization is miniemulsion polymerization in which the monomer phase is first dispersed into the aqueous phase in the form of small and stable droplets in the size range of approximately 0.05 to 0.4 microns in diameter through the use of a mixed emulsifier system. These miniemulsions are formed by the addition of a co-surfactant (for example hexadecane or cetyl alcohol) to the usual emulsion polymerization recipe, typically containing sodium dodecyl sulfate as surfactant. Initiation an polymerization then take place in the monomer droplets and the product polymer particles are approximately the same size as the initial monomer droplets. To gain a more fundamental understanding of the mechanisms involved in miniemulsion polymerizations, the PIs plan to: 1. Determine the effect of the composition of the particle/water interface and the monomer/polymer particle on the entry and exit rates of free radicals to and from the droplets/particles. 2. Test the existing methodologies for the determination of the entry and exit rate coefficients which have a direct bearing on the mechanisms of this heterogeneous polymerization. 3. Determine the relative importance of droplet/droplet, particle/droplet, and particle/particle instabilities and their influence on miniemulsion polymerization. 4. Examine the effect of the breadth in the particle/droplet size distributions through simulations of the miniemulsion polymerization kinetics, hereby approaching a more realistic description of an actual system.