Theoretical Analysis of Rates of Emulsion Polymerization

Abstract

The importance of emulsion and seeded polymerizations that proceed with a small average number of free radicals per particle (n) has recently been recognized. We now show how to generate analytical solutions to the set of differential equations that describe polymerizations for which n is small due to the rapid transfer of reactivity from the particles. The steady state approximation is not invoked. The analysis exploits methods devised originally to describe gaseous, unimolecular decomposition reactions to which the emulsion polymerizations are analogous. As an example of their usefulness the analytical solutions are applied to the seeded polymerization of vinyl acetate. It is inferred that despite the absence of new nucleation, the efficiency of free radical capture by the particles is remarkably small (< 0.1 %); possible reasons for this are discussed.