Developing a hybrid emulsion polymerization system to synthesize Fe₃O₄/polystyrene latexes with narrow size distribution and high magnetite content

A hybrid emulsion polymerization was formulated for synthesizing Fe₃O₄/polystyrene composite latex. This system, containing binary droplets that are magnetic (Mag)-droplets with a diameter of 100-200 nm and styrene (St)-droplets with a diameter of 3-4 μm, was obtained by mixing Mag-miniemulsion and St-macroemulsion. With extremely low surfactants concentration ([double less-than sign]critical micelle concentration, CMC), the nucleated loci are selectively controlled in the Mag-droplets, as the result of smaller droplet size and larger surface ratio. Both water-soluble potassium persulfate (KPS) and oil-soluble 2,2'-azobis(2-isobutyronitrile) was adopted to initiate the polymerization. In the presence of KPS, magnetic polystyrene latices with particles size of 60-200 nm, narrow size distribution, and high magnetite content (86 wt % measured by TGA) were attained successfully. The synthesized magnetic Fe₃O₄/polystyrene latices assembled into well-ordered hexagonal structure in the surface of a carbon supported copper grid. The influence of various parameters on various aspects of the as-synthesized Fe₃O₄/polystyrene was investigated in detail: type of initiator on composite morphology, feed ratio of Mag-miniemulsion and St-macroemulsion on magnetite content, and hydrophobic agent or amount of surfactant on size and size distribution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5285-5295, 2007