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

A reaction calorimeter was applied to study emulsion kinetics in a seeded e mulsion polymerization using highly sulfonated polystyrene seed latices. Se veral batches of emulsifier-free seeded emulsion polymerization were carrie d out to investigate the electrostatic repulsion and steric effect of highl y sulfonated seed particles on the average number of radicals per particle ((n) over bar) and the polymerization rate (R-p) in Interval II. Two monodi sperse seed latices with significantly different surface coverage of sodium styrene sulfonate (NaSS) were prepared from the two-stage shot-growth proc ess. After the purification of the seed latices, they were used in seeded e mulsion polymerization of styrene. From the calorimetric data, radical entr y and exit coefficients were calculated and compared with different reactio n conditions. The 'slope and intercept method' introduced by Gilbert was us ed in the calculation. The electrostatic repulsion between the oligomeric r adicals and the surface of sulfonated seed particles and the steric barrier of sulfonate-rich seed surface had significant influences on the changes o f emulsion kinetic parameters. (C) 1999 Elsevier Science B.V. All rights re served.