The process of emulsion polymerization is observed to occur in the following manner. An aqueous emulsion of monomer is prepared using a soap as the emulsifier. The addition of a catalyst starts the polymerization after an initiation period whose length depends on the mean radius of the monomer globules (long periods for large mean radius and short periods for small mean radius). As the reaction proceeds, the mean radius of the globules diminishes and the free soap concentration increases. It is believed that the initiation period is the result of the existence of an inhibitor in the monomer. The catalyst reacts with that part of the inhibitor which is dissolved in the water phase, so that in order for equilibrium to be restored some of the inhibitor must diffuse out of the monomer. Rate curves are derived on this basis using the added assumptions: (a) polymerization occurs at the monomer‐water interface after the inhibitor concentration has reached a low threshold value. (b) radius distribution function of monomer has a single maximum.
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