DISPERSION POLYMERIZATIONS IN SUPERCRITICAL CARBON-DIOXIDE

Conventional heterogeneous dispersion polymerizations of unsaturated m onomers are performed in either aqueous or organic dispersing media wi th the addition of interfacially active agents to stabilize the colloi dal dispersion that forms. Successful stabilization of the polymer col loid during polymerization results in the formation of high molar mass polymers with high rates of polymerization. An environmentally respon sible alternative to aqueous and organic dispersing media for heteroge neous dispersion polymerizations is described in which supercritical c arbon dioxide (CO2) is used in conjunction with molecularly engineered free radical initiators and amphipathic molecules that are specifical ly designed to be interfacially active in CO2. Conventional lipophilic monomers, exemplified by methyl methacrylate, can be quantitatively ( >90 percent) polymerized heterogeneously to very high degrees of polym erization (>3000) in supercritical CO2 in the presence of an added sta bilizer to form kinetically stable dispersions that result in micromet er-sized particles with a narrow size distribution.