A structural analysis of an increasing plasticity effect for polymer nanocomposites filled with carbon nanotubes was carried out. It was shown that this effect was due to densely packed interfacial layer formation on an atomic scale on the smooth nanotube surfaces, which resulted in changes in the polymer molecular matrix and structural characteristics. A prediction of the nanocomposite properties as a function of nanotube contents was obtained. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2621-2624, 2009