Emulsion polymerization of styrene using the homopolymer of a reactive surfactant

The emulsion polymerization of styrene using the homopolymer of sodium dode cyl allyl sulfosuccinate as a polymeric surfactant (poly(TREM)) was studied in terms of the polymerization kinetics, the nucleation mechanisms, and th e properties of the final latexes. It was found that the relationship betwe en the maximum rate of polymerization and the final number of polymer parti cles was one-to-one under all experimental conditions (R-p proportional to N-p(1.0)). The dependencies of these on the initiator and polymeric surfact ant concentrations varied, depending on experimental conditions (R-p propor tional to N-p(1.0) proportional to [E](0.2-0.4); R-p proportional to N-P(1. 0) proportional to [I](0.6-0-8)). These variations were attributed to the i ncreased ionic strength effects with increasing concentration of poly(TREM) , a polyelectrolyte, and its properties as a polymeric surfactant. It was i nferred from the polymerization kinetics (Rp vs time) that homogeneous nucl eation was dominant using poly(TREM) even with concentrations exceeding its critical micelle concentration. This differs from the monomeric TREM LF-40 surfactant. Characterization of the amount of poly(TREM) bound to the poly mer particles was carried out by serum replacement studies and ion exchange /conductometric titration measurements. Evidence is given that more than ha lf of the poly(TREM) was bound to the polymer particles, either by grafting of the poly(TREM) and/or irreversible adsorption. The amount of bound poly (TREM) increased with increasing surfactant concentration and increasing in itiator concentration (i.e., decreasing particle diameter). Contact angles of water measured on films formed from the latexes showed that the poly(TRE M) does not migrate significantly to the surface of the films, which is con sistent with the latex surface characterization results.