| A poly{lcub}styrene-b-(vinyl alcohol){rcub} block copolymer was synthesized using a difunctional free radical initiator, 4-(t-butylperoxycarbonyl)-3-hexyl-6-(7-(t-butylperoxycarbonyl)heptyl)cyclohexene, which contains both primary and cyclic perester peroxide groups. This block copolymer is amphipatic since it contains both polar and non-polar blocks; it is useful as a surfactant for the stabilization of polystyrene latex.; Poly{lcub}styrene-b-(vinyl acetate){rcub} was synthesized by a two stage polymerization. In the first stage, polymerization of styrene monomer was initiated by the cyclic perester of the difunctional initiator. Polystyrene initiator containing primary perester groups was formed. Polystyrene initiator was then used to initiate vinyl acetate polymerization and poly{lcub}styrene-b-(vinyl acetate){rcub} was obtained. Poly{lcub}styrene-b-(vinyl acetate){rcub} was then hydrolyzed to poly{lcub}styrene-b-(vinyl alcohol){rcub}.; The block copolymers formed were of relatively high molecular weight, but upon adding dioxane during hydrolysis, the block copolymer could be dispersed in a water-dioxane mixture, then be further diluted with water. The solution of poly{lcub}styrene-b-(vinyl alcohol){rcub} in a water-dioxane mixture was used as a polymeric surfactant solution to stabilize styrene, methyl methacrylate, and vinyl acetate monomers in emulsion polymerization. Only styrene polymerization resulted in a stable latex. This result is attributed to the chemical nature of the block copolymer. The polystyrene block can be dissolved in the polystyrene latex particle and enhances the ability of the block copolymer to stabilize the latex.; Polystyrene latex particles stabilized by poly{lcub}styrene-b-(vinyl alcohol){rcub} were studied by scanning electron microscopy. The particle sizes were large and the distributions were broad in comparison with the particles stabilized by conventional low molecular weight polymeric surfactants. |
