Copolymers of a fluorinated acrylate and styrene were synthesized to enhance the viscosity of liquid carbon dioxide. The phase behavior of mixtures of these polymers with carbon dioxide was measured at 295 K and pressures from 6.70 to 48.28 MPa. Miscibility pressures decreased with a decrease in the styrene content and increased as molecular weight increased. These polymers were also found to significantly Enhance the viscosity of carbon dioxide, by a factor of ca. 5 to 400 at concentrations from 1 to 5 wt %. The optimal composition for viscosity enhancement was 29 mol % styrene-71 mol % fluoroacrylate.