We have developed novel polyimides with high gas permeability and selectivity to prepare membranes for on board inert gas generation system (OBIGGS).Both high permeability and high selectivity are achieved by using high permeable and soluble 2,2-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) and more than two kinds of diamines.2,3,5,6-Tetramethyl-1,4-phenylenediamine (TMPD) was used to improve gas permeability and other diamines such as m-Phenylenediamine,3,4-Oxydianiline and 4,4-Methylenedianiline were used to improve gas selectivity[1].The polyimide copolymers were synthesized by commercial chemical imidization and their average molecular weights were over 100,000g/mol[2].The glass temperature (Tg) and the thermal degradation temperature were characterized using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) to confirm their superior thermal stability.The synthesized copolymers showed high Tg over 300°C and high thermal degradation temperature over 500°C.The gas permeation properties were obtained from time-lag method and ideal permeabilities of O2 and N2 and ideal selectivity of O2/N2 were measured.Compared to common polyimids having very low gas permeability lower than 1 barrer,our polyimide copolymer showed high O2 permeability of 44 barrer with high O2/N2 selectivity around 5.One example of gas permeability results are shown in Figure 1.