Free-radical transport from latex particles

A rate constant for the diffusion of monomer radicals from latex particles is derived using the transport equations describing the generation, diffusion, and reaction of monomer radicals within the particles. Calculations for styrene emulsion polymerization show that this “desorption constant” accounts for nonuniform distribution of monomer radicals within the particle while some previously published theories do not. The difference in the desorption constant calculated with the model derived in this work and the “uniform concentration” models could be an order of magnitude when diffusivity of monomer radicals in the particles is small. The monomer radical transport theory is extended to emulsion copolymerization. Desorption rate constants accounting for nonuniform distribution of monomer radicals are derived for emulsion copolymerization.