Solubility of Poly(perfluoromonoitaconates) and Poly(perfluorodiitaconates) in Supercritical CO2

Abstract

Cloud-point data are reported at 25−150 °C 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 °C, 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.