||Copolymers of poly(pentyl acrylate-co-methyl methacrylate) [P(PA-co-MMA)] were manufactured by using carbon dioxide with dispersion polymerization. The thermophysical characteristics of P(PA-co-MMA) were researched with three kinds ratios (1:20, 1:25, 1:30) of PA vs MMA and AIBN concentrations of (1.0, 2.0, 4.0) wt%. Experimental data at pressures of p ≤ 206 MPa and T ≤ 434 K was investigated for binary and ternary solution of P(PA-co-MMA) under compressed CO2, CHClF2, CHF3 and CH2F2. Experiments are carried out to get phase segregation for the binary solution of P(PA-co-MMA) [1:25, 1.0, 2.0 and 4.0 wt% AIBN] + compressed fluorine solvents (CHF3, CHClF2, CH2F2) solutions at a pressure of p < 168 MPa and at (333 ≤ T ≤ 434) K. It is revealed that the CH2F2 + P(PA-co-MMA) solution is seen as the UCST type with minus curves, while the CHClF2 + P(PA-co-MMA) and CHF3 + P(PA-co-MMA) solutions appear in the LCST region. Phase equilibria curves for P(PA-co-MMA) [Mw=198,000, 249,000, 258,000] + compressed (CHF3, CHClF2, CH2F2) solutions depict a minus curves for CH2F2 + P(PA-co-MMA) and a plus curves for the CHF3 + P(PA-co-MMA) and CHClF2 + P(PA-co-MMA) solutions at T ≤ 434 K and at p ≤ 168 MPa.