SOLUBILITY OF HOMOPOLYMERS AND COPOLYMERS IN CARBON-DIOXIDE

The cloud points of various amorphous polyether, polyacrylate, and pol ysiloxane homopolymers, and a variety of commercially available block copolymers, were measured in CO2 at temperatures from 25 to 65 degrees C and pressures of ca. 1000-6000 psia. Almost without exception, the solubility of amorphous polymers increases with a decrease in the cohe sive energy density, or likewise, the surface tension of the polymer. With this decrease in surface tension, the polymer cohesive energy den sity becomes closer to that of CO2. Consequently, solubility is govern ed primarily by polymer-polymer interactions, while polymer-CO2 intera ctions play a secondary role. The solubility is strongly dependent upo n molecular weight for the less CO2-philic polymers. The solubilities of high-molecular-weight poly(fluoroalkoxyphosphazenes) in CO2 were co mparable to those of poly(1,1-dihydroperfluorooctylacrylate), one of t he most CO2-soluble polymers known.