Kinetics of long-chain branching in emulsion polymerization: 1. Chain transfer to polymer

Abstract

New simulation models to predict the molecular weight distribution in emulsion polymerization that includes chain transfer to polymer are proposed. When the frequency of branching is not very large, the kinetics of emulsion polymerization can be modelled effectively as a large number of semibatch reactors as long as monomer droplets exist and of batch reactors after the disappearance of monomer droplets. In such cases, a simulation method based on the branching density distribution proposed earlier for non-linear polymerizations in homogeneous media shows its versatility to describe the kinetics of non-linear emulsion polymerization. However, the calculated results based on a direct simulation model that simulates all polymer molecules in each polymer particle clearly show that the fact that each polymer particle consists of a limited number of polymer molecules must be accounted for as the branching density increases. In general, such compartmentalization effects are important when one considers the molecular weight distribution development of non-linear polymer chains that are formed in emulsion polymerization.