Melt mixed composites based on polyamide 12 (PA12) were prepared using single wall carbon nanotubes (SWNT), which were encapsulated by styrene maleic anhydride copolymer (SMA). The aim was to achieve a reactive coupling between the maleic anhydride functionality of SMA at the surface of the SWNT and the amine end groups of PA12 during the melt mixing. The reaction could be proven by infrared spectroscopy. The modified nanocomposites exhibited a better SWNT dispersion. An enhanced interfacial adhesion between PA12 and SWNT was detected from SEM investigations of tensile fractured surfaces of the SMA encapsulated PA12/SWNT composites. Electrical conductivity measurements revealed the formation of "network-like" structure formation at 6 wt % SWNT content in PA12/SWNT composites, however, PA12/SWNT + SMA composites showed insulating behavior due to encapsulating SMA layer on SWNT surface. Studies on crystallization behavior indicated the nucleating action of unmodified and SMA encapsulated SWNT in the respective composites as found in the increase of crystallization temperature and the change in the crystalline morphology of PA12 as observed from DSC, WAXD, and SAXS. However, the degree of crystallinity of PA12 increased only marginally on incorporation of either unmodified or SMA encapsulated SWNT. (c) 2007 Wiley Periodicals, Inc.