C60/polyaniline (PANI) nanocomposites have been synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in the presence of C60 by using an interfacial reaction. When compared with the pure PANI nanofibers from the similar process, the diameter of the obtained C60/PANI nanofibers was increased because of the encapsulation of C60 into PANI during aniline polymerization, which resulted from the charge-transfer interactions between C60 and aniline fragment in PANI. In addition, the resulting C60/PANI nanocomposites synthesized from the low initial C60/aniline molar ratio (less than 1:25) showed the homogenous morphology composed of fiber network structures, which has an electrical conductivity as high as 1.1 x 10-4 S/cm. However, the C60/PANI nanocomposites from the higher initial C60/aniline molar ratio (more than 1:15) showed the nonuniformly distributed morphology, and the electrical conductivity was decreased to 3.5 x 10-5 S/cm. Moreover, the C60/PANI nanocomposites from the interfacial reaction showed a higher value of electrical conductivity than the mechanically mixed C60/PANI blends with the same C60 content, because of the more evenly distributed microstructures. FTIR, UVvis, and CV data confirmed the presence of C60 and the significant charge-transfer interactions in the resultant nanocomposites, which was responsible for the morphology development of the C60/PANI and the variation of the electrical conductivity. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012