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Interfacially active block copolymer amphiphiles have been synthesized and their self-assembly into micelles in supercritical carbon dioxide (CO₂) has been demonstrated with small-angle neutron scattering (SANS). These materials establish the design criteria for molecularly engineered surfactants that can stabilize and disperse otherwise insoluble matter into a CO₂ continuous phase. Polystyrene-b-poly(1,1-dihydroperfluorooctyl acrylate) copolymers self-assembled into polydisperse core-shell-type micelles as a result of the disparate solubility characteristics of the different block segments in CO₂. These nonionic surfactants for CO₂ were shown by SANS to be capable of emulsifying up to 20 percent by weight of a CO₂-insoluble hydrocarbon into CO₂. This result demonstrates the efficacy of surfactant-modified CO₂ in reducing the large volumes of organic and halogenated solvent waste streams released into …