Abstract : Thermodynamically stable nanostructured and co-continuous blends are synthesized by reactive blending of functionalized polyethylene (FPE) and a bimodal mixture of short and long chains of polyamide 6 (PA). The short chains react more readily to form graft copolymers and facilitate both grafting of long chains and formation of nanostructures. The grafting and the incorporation of long PA chains should introduce entanglements and tie molecules between the PA crystallites. A two step selective extraction enables to characterize the graft copolymers and the non-reacted FPE and PA chains. The macroscopic properties of these blends are optimized by modifying the feeding mode of the raw materials, by the blending conditions and by the PA phase composition. A structural study of the blends and the graft copolymers clarifies the chain organization both nanostructures. The FPE and PA phases crystallize in these confined morphologies, giving rise to outstanding mechanical properties to the blends. At low strains and for temperatures higher than the FPE melting, the blends having a composition of 64/36 FPE/PA in weight display a thermomechanical resistance of about twenty megapascals. The PA long chains play the role of tie molecules between crystallites and improve the ductility of the nanostructured blends at high temperature (ultimate strain of 250% at 150°C). We performed X-rays scattering experiments and transmission electron microscopy before and after tensile test and we correlated the structural and morphology evolution of blends with the mechanical behavior.