Tailor-made block copolymer nanocomposite membranes are prepared by incorporation of 40 wt% methoxy poly(ethylene glycol) (PEG) functionalized polyoctahedral oligomeric silsesquioxanes (POSS) nanoparticles in commercial thermoplastic elastomer multiblock copolymer PEBAX (R) MH 1657. Atomic force microscopy was used to find out the location of the nanoparticles in the block copolymer matrix. Separation of CO2 from N-2 and H-2 is studied by measurements of single gas transport properties of nanocomposite materials using the time-lag method in the temperature range 30-70 degrees C. PEG functionalized POSS nanoparticles increase the CO2 permeability of the nanocomposite membranes without loss of CO2/N-2 and CO2/H-2 selectivity. Thermal properties of the nanocomposite membranes are studied by differential scanning calorimetry (DSC) to assess the stability of the nanocomposite membranes upon melting of polyether and polyamide blocks. (C) 2014 Elsevier B.V. All rights reserved.