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PMMA encapsulated silica particles were synthesized by the dispersion polymerization of MMA in supercritical carbon dioxide (scCO 2 ). Nanosized silica particles pretreated with 3-(trimethoxysilyl) propyl methacrylate (g-MPS) were used as seeds in the polymerization. Polymeric stabilizer, poly(dimethylsiloxane)-b-poly (methacrylic acid) (PDMS-b-PMA) copolymer provided sufficient stabilization to the silica/PMMA composite latexes in scCO 2 to produce spherical particles. SEM and TEM analysis revealed that the composite particles have core-shell type morphology.

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A series of random copolymers, composed of 1H,1H‐perfluorooctyl methacrylate (FOMA) and 2‐dimethylaminoethyl methacrylate (DMAEMA) were prepared as stabilizers for the dispersion polymerization of methyl methacrylate in supercritical CO2 (scCO2). Free‐flowing, spherical poly(methyl methacrylate) (PMMA) particles were produced in high yield by the effective stabilization of poly(FOMA‐co‐DMAEMA) containing 34–67 w/w % (15–41 m/m %) FOMA structural units. Less stabilized but micron‐sized discrete particles could be obtained even with 25 w/w % (10 m/m %) FOMA stabilizer. The result showed that the composition of copolymeric stabilizers had a dramatic effect on the size and morphology of PMMA. The particle size was controllable with the surfactant concentration. The effect of the monomer concentration and the initial pressure on the polymerization was also investigated. The dry polymer powder obtained from dispersion polymerization could be redispersed to form stable aqueous latexes in an acidic buffered solution (pH = 2.1) by an electrostatic stabilization mechanism due to the ionization of DMAEMA units in the stabilizer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1365–1375, 2008