Emulsion polymerization classical concepts

The reaction described in this example is carried out in miniemulsion.Miniemulsions are dispersions of critically stabilized oil droplets with a size between 50 and 500 nm prepared by shearing a system containing oil, water,a surfactant and a hydrophobe. In contrast to the classical emulsion polymerization (see 5ect. 2.2.4.2), here the polymerization starts and proceeds directly within the preformed micellar "nanoreactors" (= monomer droplets).This means that the droplets have to become the primary locus of the nucleation of the polymer reaction. With the concept of "nanoreactors" one can take advantage of a potential thermodynamic control for the design of nanoparticles. Polymerizations in such miniemulsions, when carefully prepared, result in latex particles which have about the same size as the initial droplets.The polymerization of miniemulsions extends the possibilities of the widely applied emulsion polymerization and provides advantages with respect to copolymerization reactions of monomers with different polarity, incorporation of hydrophobic materials, or with respect to the stability of the formed latexes. 

The course of the reaction mte/time function, measured by us, is exactly like the course of the same function in the case of the catalyzed emulsion polymerization of styrene. The small dependence of Ubf on the initiation rate in the period of zero order, which was observed by us, agrees well with classical conceptions The period of particle formation is over and the radicals formed now affect initiation and termination likewise. Therefore the initiation rate can not influence the reaction rate. (Actually the reaction rate increases somewhat, on strongly increasing the dose rate. This shows that the mean radical concentration, n, in the particles is slightly higher than 0.5. The termination reaction is already retarded.)... 

The situation, characterized by Eq. (23), represents an idealized state. In many cases, the concept of the classical kinetic model of emulsion polymerization has been modified because it was found to be inapplicable to monomers with higher water solubility [25, 67, 69]. The polymerization of partly water-soluble monomers was assumed to proceed not only in the micelles or particles but also in the continuous aqueous phase. 

---