A series of graft copolymers, poly(methyl methacrylate-co-hydroxyethyl methacrylate)-g-poly(perfluoropropylene oxide), was synthesized for application as stabilizers in dispersion polymerization of methyl methacrylate in supercritical carbon dioxide. The backbone, poly(methyl methacrylate-co-hydroxyethyl methacrylate), is effectively insoluble in carbon dioxide and the grafted chains, poly(perfluoropropylene oxide), are completely miscible in carbon dioxide at moderate pressures. The effect of molecular architecture on polymerization rate and PMMA. particle size was evaluated by varying the molecular weight of the anchor group (backbone of the copolymer), molecular weight of the CO2-soluble graft chain, and graft chain density. The efficiency of the graft copolymers as dispersants was demonstrated as micron-size polymer beads of molecular weight greater than 100000 were produced. The results showed that a careful balance between anchor group size (backbone length) and amount of soluble component (either graft chain length or graft chain density) is necessary but not sufficient to achieve adequate stabilization and that the distribution of the soluble component along the anchor group was also important. Furthermore, the backbone molecular weight was shown as the key component for stabilization, provided that enough CO2-philic component has been included to ensure solubility.