Cloud-point data to 270 °C and 2800 bar are presented for poly(vinylidene fluoride- co -22.0 mol % hexafluoropropylene) (Fluorel) in supercritical fluid (SCF) C 3 F 6, CClF 3, CHF 3, and CO 2 . The impact of backbone architecture on intermolecular interactions and fluorocopolymer solubility is determined by comparing the phase behavior of Fluorel to that of poly(tetrafluoroethylene- co -19.3 mol % hexafluoropropylene) (FEP 19 ) in the same SCF solvents. Good solvents for nonpolar FEP 19 (SF 6 and C 3 F 8 ) did not dissolve polar Fluorel even at temperatures in excess of 260 °C. Although the small dipole moments of C 3 F 6 and CClF 3 interact favorably with the polar, vinylidene fluoride segments of Fluorel, the cloud-point curves in these two solvents exhibit a sharp rise in cloud-point pressures as the temperature is decreased. Apparently, dipolar interactions between vinylidene fluoride segments are much stronger than Fluorel−C 3 F 6 or Fluorel−CClF 3 cross-interactions as the temperature is lowered. In contrast, quadrupolar CO 2 and dipolar CHF 3 are good solvents for Fluorel due to favorable polar, vinylidene fluoride segment−SCF solvent cross-interactions. However, at or near room temperature, CO 2 is a much better solvent for Fluorel than is CHF 3, which is speculated to be a result of specific interactions between CO 2 and the vinylidene fluoride segments.
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Mertdogan et al. (1997) studied this question.
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