Copolymerization of Tetrafluoroethylene and 2,2-Bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole in Supercritical Carbon Dioxide

Copolymers of tetrafluoroethylene (TFE) and 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole (PDD) were synthesized in carbon dioxide at low temperatures. Bis(perfluoro-2-N-propoxypropionyl) peroxide was used as initiator. A range of copolymers with various compositions and different molecular weights were prepared in yields as high as 74%. The glass transition temperature of the copolymers increased with increasing PDD content and ranged from 67 to 334 °C for the PDD homopolymer. The phase behavior was found to depend on the feed composition. A comparison of a fully fluorinated commercially available product with a sample synthesized in carbon dioxide (without post-fluorination procedures) to match the composition and the molecular weight of the commercial sample showed no significant difference using IR spectroscopy, NMR spectroscopy, and differential scanning calorimetry, indicating similar microstructures. A simple method to determine the copolymer composition based on infrared spectroscopy was developed.