Monomer Concentration in Polymer Particles in Emulsion Polymerization

The rate of an emulsion polymerization depends on the monomer concentration at the locus of polymerization in the polymer particles. This note suggests a shortcut method of specifying monomer concentration for new monomers, or monomers for which thermodynamic swelling data is unavailable. While the monomer concentration in a polymer particle in moles per liter varies widely, when described as volume fraction monomer, the variance is much smaller. In fact, for ten monomers for which experimental values are available, the volume fraction monomer in a polymer particle in equilibrium with an aqueous phase saturated with monomer of that polymer is 0.67 +/- 0.04. Hence, if no other value is available, one could assume a monomer volume fraction monomer of 0.67 with a good degree of accuracy.

Automated summary

The rate of emulsion polymerization is influenced by the monomer concentration at the locus of polymerization in the polymer particles. This note provides a shortcut method for specifying monomer concentration for new monomers or those without thermodynamic swelling data. When described in terms of volume fraction monomer, the variance in monomer concentration in polymer particles is much smaller, with an average volume fraction monomer of 0.67 +/- 0.04 for ten monomers based on experimental values.