Polyimide (PI) nanocomposites with 4,4-bisphenol A dianhydride, 4,4-oxydiphthalic anhydride, and diaminodiphenyl methane (MDA) as comonomers and functionalized with graphene oxide (GO), were prepared by in situ polymerization. Only a small amount of GO (0.030.12 wt %) is added to improve the mechanical properties of PI and to avoid a substantial decrease of PI transparence. The nanocomposites are characterized by FTIR, X-ray diffraction, thermogravimetric analysis, transmission electron microscope, tensile test, and UV-vis spectroscopy. It is demonstrated that the PI/GO composite films possess transmittance of above 80% at wavelengths of 500800 nm when the GO content is under 0.12 wt %, while the stress intensity and Young's modulus are improved by 29 and 25%, respectively. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013