DESIGN OF NONIONIC SURFACTANTS FOR SUPERCRITICAL CARBON-DIOXIDE

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 engin eered surfactants that can stabilize and disperse otherwise insoluble matter into a CO2 continuous phase. Polystyrene-b-poly(1,1-dihydroperf luorooctyl acrylate) copolymers self-assembled into polydisperse core- shell-type micelles as a result of the disparate solubility characteri stics of the different block segments in CO2. These nonionic surfactan ts for CO2 were shown by SANS to be capable of emulsifying up to 20 pe rcent by weight of a CO2-insoluble hydrocarbon into CO2. This result d emonstrates the efficacy of surfactant-modified CO2 in reducing the la rge volumes of organic and halogenated solvent waste streams released into our environment by solvent-intensive manufacturing and process in dustries.