Experimental cloud-point data up to 478 K and 248.0 MPa are reported for binary and ternary mixtures of poly(2-ethylhexyl methacrylate) (1) + carbon dioxide (2) + 2-ethylhexyl methacrylate (3) and poly(2-ethylhexyl acrylate) (1) + carbon dioxide (2) + 2-ethylhexyl acrylate (3) systems. High-pressure cloud-point data are also reported for poly(2-ethylhexyl methacrylate) and poly(2-ethylhexyl acrylate) in supercritical propane, propylene, butane, 1-butene, and dimethyl ether. Cloud-point behavior for the poly(2-ethylhexyl methacrylate) (1) + carbon dioxide (2) + 2-ethylhexyl methacrylate (3) system were measured in changes of the pressure, temperature (p, T) slope and with 2-ethylhexyl methacrylate mass fraction of w(3) = 0.0, 0.201, 0.303, and 0.564. With w(3) = 0.666 2-ethylhexyl methacrylate to the poly(2-ethylhexyl methacrylate) (1) + carbon dioxide (2) solution, the cloud-point curves take on the appearance of a typical lower critical solution temperature boundary. The poly(2-ethylhexyl acrylate) (1) + carbon dioxide (2) + w(3) = 0.0, 0.097, 0.206, 0.409, 0.552, and 0.604 2-ethylhexyl acrylate (3) systems change the (p, T) curve from upper critical solution temperature region to lower critical solution temperature region as the 2-ethylhexyl acrylate mass fraction increases. For w(3) = 0.709 2-ethylhexyl acrylate, the poly(2-ethylhexyl acrylate) (1) + carbon dioxide (2) solution significantly changes the phase behavior. Also, the impact by dimethyl ether mass fraction for the poly(2-ethylhexyl methacrylate) (1) and poly(2-ethylhexyl acrylate) (1) + carbon dioxide (2) + dimethyl ether (3) system is measured at temperatures to 455 K and a pressure range of (4.3 to 248.0) MPa. Pressure, composition (p, x) isotherms are obtained for the carbon dioxide (1) + 2-ethylhexyl methacrylate (2) systems at (313.15, 333.15, 353.15, 373.15, and 393.15) K and pressure up to 20.5 MPa. The carbon dioxide (1) + 2-ethylhexyl methacrylate (2) systems exhibit type-I phase behavior with a continuous mixture critical curve. The experimental results for carbon dioxide (1) + 2-ethylhexyl methacrylate (2) mixtures are modeled using the Peng-Robinson equation of state with two adjustable parameters.