Copolyimides were synthesized from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 1,3-bis(3-aminophenoxy)benzene (BAPB) with different mole ratios of 2,2-bis[4-(4- aminophenoxy)phenyl]hexafluoropropane (BAPP). The solution cast film of poly(amic acid)(PAA) was heat treated at different temperatures to create copolyimide films. The PI copolymer films were found to exhibit good optical transparencies. The thermomechanical properties, morphology, and optical transparency of PI films were examined using fourier transform infrared spectroscopy(FT-IR), wide-angle X-ray diffraction (XRD), scanning electron microscopes(SEM), differential scanning calorimeter(DSC), thermogravimetric analyzer(TGA), universal tensile machine(UTM), and UV-Vis. spectrometer. The glass transition temperature(Tg), ultimate strength, and initial modulus linearly increased with increasing BAPP mole fraction. However, thermal stability(TDi) of the copolyimide remains constant regardless of BAPP loadings. It was found, however, that the optical transparency decreases slightly upon increasing the BAPP content because of the formation of the charge transfer complexes.