Industrial & Engineering Chemistry Research, Vol.42, No.25, 6499-6504, 2003
Solubility of poly(perfluoromonoitaconates) and poly (perfluorodiitaconates) in supercritical CO2
Cloud-point data are reported at 25-150 degreesC and 100-560 bar for poly(perfluoromonoitaconates) (PFMITn) and poly(perfluorodiitaconates) (PFDITn, where n, the number CF2 groups in the alkyl side chain, is equal to 3, 5, 7, and 9 for both types of itaconates) in supercritical CO2. Cloud-point curves for the PFMITn-CO2 system shift to lower pressures as the fluorinated alkyl tail length increases; however, this trend reverses going from PFMIT7 to PFMIT9. Hence, there is an optimum fluorocarbon side-chain length that balances energetic polymer-polymer, CO2-CO2, and polymer-CO2 interactions with a favorable entropic effect associated with the increased free volume of the longer side chains. The PFDITn polymers readily dissolve in CO2 at pressures as low as 140 bar at 25 degreesC, although, in this case, the cloud-point curves all superpose. The cloud-point data suggest that supercritical CO2 is a suitable solvent for processing these fluoropolymers.