Seeded emulsion polymerization of styrene: Influence of acrylic acid on the particle growth process

The seeded batch emulsion copolymerization of styrene and acrylic acid was studied. The polymerization rate was investigated with pH as the main param eter. Some attempts were made to evaluate the average number of growing cha ins per particle during Stage II of the emulsion polymerization process. Th e final latex produces were characterized by means of conductometric aqueou s titration and potentiometric titration in an organic solvent mixture. The distribution of the acid groups over the aqueous phase, the particle surfa ce, and the interior of the particles together with the kinetic results pro vided insight into important features governing the incorporation of acryli c acid. The results indicate that pH is the dominating parameter for the in corporation process. An optimal incorporation on the surface of the particl es is observed for a low value of pH. In that case, all the acid groups are protonated. (C) 2000 John Wiley & Sons, Inc.