Poly(ether-block-amide) (PEBA), commercially known as PEBAX (R), nanocomposites filled with organically modified clay (Cloisite 30B) and trisilinolphenyl-polyhedral oligomeric silsesquioxane (tsp-POSS) were prepared by a melt mixing method, respectively. The structures of the nanocomposites were investigated using differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and in-situ simultaneous small and wide angle X-ray scatterings (SAXS and WAXS) during uniaxial deformation. The FT-IR spectra showed the hydrogen bonding between the fillers and the PEBA which helped to disperse the fillers in the polymer matrix. The crystallinities and mechanical properties of the nanocomposites were improved compared to the neat polymer. Their origins were studied with an in-situ simultaneous SAXS and WAXS technique during the uniaxial deformation. (c) 2012 Elsevier Ltd. All rights reserved.