Phase equilibria of binary and ternary mixtures with poly(styrene-co-hexafluorobutyl methacrylate) and solvents at high pressure and temperature

This paper presents the synthesis of the fluoric copolymer poly(styrene-co-2,2,3,4,4,4-hexafluorobutyl methacrylate) [P(styrene-co-HFBMA)] through dispersed phase polymerization in a supercritical carbon dioxide (sc-CO₂) medium. The physiochemical characteristics of P(styrene-co-HFBMA) were extensively studied by varying the styrene to HFBMA mole ratios (40:1, 25:1, and 20:1) and 2,2'-Azobisisobutyronitrile (AIBN) initiator at different mass percentages (mass%) from 1 to 4, along with the mean molecular mass (M_m). Phase transition data were reported for two-component and three-component P(styrene-co-HFBMA) in sc-C₃H₈, C₃H₆, C₄H₁₀, and C₄H₈, encompassing temperature “T” and pressure “P” limits (∼341 to ∼459) K, and (∼21 to ∼185) MPa, respectively. The phase behavior of the P(styrene-co-HFBMA) + solvent mixtures displayed an upper critical solution temperature (UCST) type behavior with a declining gradient. Equilibria curves were measured for the P(styrene-co-HFBMA) + (C₃H₁₀/C₃H₆) + CH₃OCH₃(i.e., DME) (25:1, AIBN mass%: 2.0) system in “P-T” phase diagram, spanning from the UCST region to LCST region at DME mass% ranging from 0.0 to 68.5. Additionally, solubility curves at “P”: up to ∼148 MPa and “T”: from ∼450 K to ∼350 K showed a shift from a declining slope to an inclined slope within the 0.0 to 60.3 mass% range for the P(styrene-co-HFBMA) (mole ratio:25:1; AIBN mass%: 2.0) + (C₄H₁₀/C₄H₈) + DME system. These findings provide valuable insights into the phase behavior and solubility characteristics of the P(styrene-co-HFBMA) copolymer in different sc-solvent mixtures.