ABSTRACT
This chapter discusses the molecular mechanisms of the most important processes taking place in heterophase polymerization, and aims at providing a clear molecular picture of heterophase polymerization as a whole. The first possible mechanism of particle formation is the collapse of a single polymer chain initially dissolved in the continuous phase. Even though the original idea of precipitation nucleation was developed for radical emulsion polymerization, the general concept is valid for any other type of heterophase polymerization. Heterogeneous nucleation is a situation where at least three different components participate: the continuous phase, the aggregates of the nucleating species, and the foreign particle. The size distribution of the particles in heterophase polymerization is influenced by particle formation, molecular transfer, and polymerization, but also by particle aggregation and breakage. The mechanism of particle aggregation is basically the same as that of molecular capture or molecular absorption: the collision between two different entities after they diffuse toward each other following random-walk trajectories.
