The gas permeability of carbon dioxide, oxygen and nitrogen for hyperbranched polyimide (HBPI) containing trifluoromethyl groups were investigated. The H13Pls were prepared by condensation polymerization of a triamine monomer, 1,3,5-tris(2-trifluoromethyl-4-amino-phenoxy) benzene (TFAPOB) and a commercially available dianhydricle monomer 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA). With different monomer addition methods and different monomer molar ratios, amine terminated HBPI (AM-HQDPA) and anhydride terminated HBPI (AD-HQDPA) were obtained, subsequently, the trifluoromethylphenyl amine terminated HBPI (CF3-HQDPA) was achieved by modifying the end groups of AD-HQDPA with (3,5-ditrifluoromethyl)aniline. The CF3-HQDPA exhibited a good mechanical and thermal stability as well as AM-HQDPA, and showed better gas permeabilities than that of AM-HQDPA because of increase of free volume contributed by the bulky trifluoromethyl group introduced, but, the selectivity of CF3-HQDPA was lower than that of AM-HQDPA. This result was consistent with the trade-off relationship. (c) 2008 Wiley Periodicals, Inc.