Dispersion Polymerizations in Supercritical Carbon Dioxide

• Published in: Science (American Association for the Advancement of Science) Vol. 265; no. 5170; pp. 356 - 359
• Main Authors: DeSimone, J. M., Maury, E. E., Menceloglu, Y. Z., McClain, J. B., Romack, T. J., Combes, J. R.
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Society for the Advancement of Science 15.07.1994; Amer Assoc Advancement Science; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Additives; Applied sciences; Carbon dioxide; Chemistry; Climate; Colloids; Exact sciences and technology; Functional groups; Inhalants; Monomers; Multidisciplinary Sciences; Organic Chemistry; Organic polymers; Physicochemistry of polymers; Plasticizers; Plastics; Plastics additives; Polymerization; Polymers; Preparation, kinetics, thermodynamics, mechanism and catalysts; Science & Technology; Science & Technology - Other Topics; Scientific Concepts; Solvents; Stabilizing agents; Surfactants; Teeth; Water; PROPANE; PHASE-BEHAVIOR; MICROEMULSIONS; POLYMER; Supercritical solvent; Carbon dioxide; Dispersion polymerization
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.265.5170.356

Conventional heterogeneous dispersion polymerizations of unsaturated monomers are performed in either aqueous or organic dispersing media with the addition of interfacially active agents to stabilize the colloidal dispersion that forms. Successful stabilization of the polymer colloid during polymerization results in the formation of high molar mass polymers with high rates of polymerization. An environmentally responsible alternative to aqueous and organic dispersing media for heterogeneous dispersion polymerizations is described in which supercritical carbon dioxide (CO$_2$) is used in conjunction with molecularly engineered free radical initiators and amphipathic molecules that are specifically designed to be interfacially active in CO$_2$. Conventional lipophilic monomers, exemplified by methyl methacrylate, can be quantitatively (>90 percent) polymerized heterogeneously to very high degrees of polymerization (>3000) in supercritical CO$_2$ in the presence of an added stabilizer to form kinetically stable dispersions that result in micrometer-sized particles with a narrow size distribution.