Polyimide (PI)/poly(N-ethyl aniline-co-aniline-2-sulfonic acid)clay (SPNEAC) nanocomposite films containing water-soluble SPNEAC were successfully synthesized. Atomic force microscopy studies showed a homogeneous distribution of coated clay particles in the PI matrix. The particle sizes varied between about 50 nm and about 220 nm in height and 67 m in length in the nanocomposite containing 5 wt % SPNEAC. Average surface roughnesses of 0.253 and 34.9 nm were obtained for neat PI and the 5 wt % SPNEACPI nanocomposite, respectively. Dynamic mechanical spectrometry was used to study the viscoelastic transitions and their temperatures. The dynamic mechanical spectrometry results show a decreasing glass-transition temperature of the nanocomposites with increasing SPNEAC weight fraction. The area under the -transition peak, which is associated with damping and impact energy, increased with increasing SPNEAC weight fraction. The impact energy of the nanocomposites was estimated with a viscoelastic model. It increased with increasing SPNEAC weight fraction, and a maximum value of 84.9 mJ was obtained. The viscoelastic model was based on the area under the -transition peak, rubbery plateau modulus, and sample volume. A 5 wt % addition of SPNEAC improved the impact energy of neat PI films by 300%. Scanning electron micrographs of the nanocomposite films showed a less compact cross-sectional morphology. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013