Two sets of soluble high performance polyimides synthesized from 2,2＇-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2＇-(trifluoromethyl)4,4＇-diaminobiphenyl diamine (PFMB), and from 2,2＇-bis(trifluoromethyl)-4,4＇,5,5＇-biphenyl-tetracarboxylic dianhydride (HFBPDA) and 2,2 ＇-(trifluoromethyl) -4,4＇-diaminobiphenyl diamine (PFMB) have been investigated by static and dynamic laser Light scattering (LLS) in tetrahydrofuran (THF) at 30 degrees C. The calibrations, for 6FDA-PFMB: (nm) = 3.87 x 10(-2) (0.568), (nm) = 2.38 x 10(-2) (0.560) and (cm(2)/s) = 2.13 x 10(-4) (-0.560); for HFBPDA-PFMB: (nm) = 2.24 x 10(-2) (0.626), (nm) = 1.27 x 10(-2) (0.621) and (cm(2)/s) = 3.99 x 10(-4) (-0.621), have been established, where , and are the weight-average molar mass, the root mean square z-average radius of gyration, the z-average hydrodynamic radius and the z-average translational diffusion coefficient, respectively. A combination of and the translational diffusion coefficient distribution G(D) leads to the calibrations of D (cm(2)/s) = 2.41 x 10(-4)M(-0.564) and D (cm(2)/s) = 6.16 x 10(-4)M(-0.656) for 6FDA-PFMB and HFBPDA-PFMB, respectively, where D and M correspond to monodisperse species. With these calibrations, we can convert a translational diffusion coefficient distribution G(D) into a corresponding molar mass distribution f(w)(M). On the basis of the Kratky-Porod wormlike chain model, the persistence lengths (q) were found to be similar to 3.3 nm and similar to 4.5 nm, respectively, for 6FDA-PFMB and HFBPDA-PFMB, which indicates that both polyimide chains have an extended conformation. In addition, / similar to (1.7-1.9) shows that they are in coil conformation. Therefore, we conclude that both polyimides have an extended coil conformation.