Experimental cloud-point data up to 205 degrees C and 2300 bar are measured for binary and ternary mixtures of poly( decyl acrylate) [ poly( DA)]- supercritical solvents-decyl acrylate ( DA) and poly( decyl methacrylate) [ poly( DMA)]- CO2- decyl methacrylate ( DMA). Also, the cloud-point curves show the binary mixtures for poly( DA) in supercritical CO2, propane, propylene, butane, 1-butene, and dimethyl ether (DME). The phase behaviors for the poly( DMA)- CO2- DMA system are measured in changes of the pressure-temperature (P-T) slope and with DMA concentrations of 4.4, 6.7, 11.2, 22.8, and 32.9 wt %. Adding 41.6 wt % DMA to the poly( DMA)- CO2 solution significantly changes the phase behavior; the curves take on the appearance of a typical LCST boundary. The cloud-point curves for the poly( DA)- CO2 system with 0, 7.5, 14.9, 23.4, and 34.9 wt % DA changes the P-T curve from an upper critical solution temperature (UCST) region to a lower critical solution temperature (LCST) region as the decyl acrylate concentration increases. Adding 40.2 wt % DA to the poly( DA)- CO2 solution significantly changes the phase behavior. The cloud-point curve takes on the appearance of a typical lower LCST region. High-pressure phase behavior data are obtained for the CO2- DA and CO2- DMA systems at temperatures in the range 40-120 degrees C and pressures up to 189 bar. The CO2- DA and CO2- DMA systems exhibit type-I phase behavior with a continuous mixture-critical curve. The experimental results for the CO2- DA and CO2- DMA mixtures are modeled using the Peng-Robinson equation of state. A good fit of the data is obtained from the Peng-Robinson equation of state using two adjustable parameters for CO2-DA and CO2- DMA systems.