Propylene/propane mixtures separation experiments by gas permeation through dense films composed of 6FDA-DAPF (a fluorinated polyimide resulting from the polycondensation of 2,2'-Bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and di-9,9'(4 aminophenyl fluorene) have been carried out.

The influence of various synthetis parameters of 6FDA-DAPF such as polymerization routes (chemically or thermally induced), polymerization solvents, casting solvents as well as heating post-treatements have been studied. This polymer offers high propylene/propane selectivities, even at high hydrocarbon partial pressures, as well as high propylene permeabilities.