Synthesis of Monodisperse Polystyrene Microlatexes by Emulsion Polymerization Using a Polymerizable Surfactant

Synthesis of monodisperse polystyrene microlatexes by emulsion polymerization using a polymerizable surfactant, ω-methoxypoly(ethylene oxide) 40 undecyl α-methacrylate macromonomer (PEO-R-MA-40), has been investigated. PEO-R-MA-40 copolymerized readily with styrene. The locus of the copolymerization is believed to occur near the surface of styrene-swollen micelles/particles where the polymerizable end groups (methacrylate) of PEO-R-MA-40 were concentrated due to its hydrophilicity. The latexes became stabilized when only about 6 wt % styrene and 10.5 wt % PEO-R-MA-40 were copolymerized. From the XPS results, it shows that only about 22% of the latex surface occupied by the copolymerized PEO-R-MA-40 was sufficient to stabilize the latex particles. Toward the completion of the copolymerization, about 80% of the latex surface was enriched by the copolymerized PEO-R-MA-40. Nearly monodisperse latex particles with diameters ranging from about 30 to 90 nm were obtained by lowering the feed weight-ratio of PEO-R-MA-40 to styrene from 1/2 to 1/8. But the particle size did not seem to be affected by the increase of KPS concentration from 0.5 to 3.0 mM at the feed ratio of 1/8. A polymerization scheme is presented to account for the results.