New stabilizers for the dispersion polymerization of methyl methacrylate (MMA) in supercritical carbon dioxide (scCO 2 ) were prepared and studied in terms of their anchor group architecture. The same perfluoropolyether (PFPE) chain was used in each case as the CO 2 -philic portion of the stabilizer and four different PMMA-philic headgroups were investigated as anchoring units: an alcohol, an acetate group, a methacrylate unit, and a PMMA block. When compared to the stabilizing ability of PFPE−alcohol, incorporation of an anchor group as small as an acetate group, or a reactive group such as a methacrylate unit, was found to have a dramatic effect upon the dispersion polymerization of MMA in scCO 2 . Their incorporation led to a significant increase in PMMA yield and molecular weight and an improvement of the morphology of the polymer product. A method for the synthesis of PFPE- b -PMMA diblock copolymers is reported via atom transfer radical polymerization (ATRP) from a PFPE−bromoester macroinitiator in a fluorinated solvent (pentafluorobutane). This method allows the controlled synthesis of PFPE- b -PMMA diblock copolymers with well-defined architecture. These copolymers were found to be effective stabilizers in scCO 2, leading to excellent PMMA yield with high molecular weight and a fine morphology. The effect of PFPE and PMMA block length on the copolymer stabilizing ability was also studied to probe the influence of the stabilizer anchor-soluble balance (ASB). In addition, the phase behavior of each stabilizer in CO 2 or a mixture of CO 2 /MMA was studied to elucidate the effect of stabilizer structure on CO 2 -philicity and stabilizing ability.
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Woods et al. (2005) studied this question.
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