Free Radical Entry in Emulsion Polymerization: A Comprehensive Theory

Abstract

A comprehensive mathematical model for radical entry into polymer particles is proposed that includes equations and various mechanistic precepts from several works, including those of the author. The model allows estimating the contribution of the different initiator-derived radicals to the overall particle entry rate (ρ). The results of the model are consistent with experimental data reported in the literature. Contrary to what is established by one of the most accepted theories, it is obtained that: 1) the determining step of the entry of water-soluble oligoradicals is not their propagation in the aqueous phase but rather their diffusion and subsequent irreversible adsorption on the particles; 2) primary particles can also enter (coagulate) and contribute to the ρ value; 3) the electrostatic repulsion between oligoradicals and charged particles plays a very important role in determining the predominant species entering the particles.