Investigation of seeded emulsion polymerization using a calorimetric method: Effects of the surface charge density on polymerization rate and average number of radicals per particle

A reaction calorimeter was applied to study emulsion kinetics in a seeded emulsion polymerization using highly sulfonated polystyrene seed latices. Several batches of emulsifier-free seeded emulsion polymerization were carried out to investigate the electrostatic repulsion and steric effect of highly sulfonated seed particles on the average number of radicals per particle (n) and the polymerization rate (R(p)) in Interval II. Two monodisperse seed latices with significantly different surface coverage of sodium styrene sulfonate (NaSS) were prepared from the two-stage shot-growth process. After the purification of the seed latices, they were used in seeded emulsion polymerization of styrene. From the calorimetric data, radical entry and exit coefficients were calculated and compared with different reaction conditions. The 'slope and intercept method' introduced by Gilbert was used in the calculation. The electrostatic repulsion between the oligomeric radicals and the surface of sulfonated seed particles and the steric barrier of sulfonate-rich seed surface had significant influences on the changes of emulsion kinetic parameters. Copyright (C) 1999 Elsevier Science B.V. All rights reserved.