Polypropylene (PP) nanocomposites with three different functionalized-multiwalled nanotubes (F-MWNTs) are compared in terms of their thermomechanical properties, morphology, oxygen permeability, and optical transparency. The F-MWNTs dodecanol-MWNT, dodecylamine-MWNT, and 1,1,1, 3,3,3-hexafluoro-2-phenyl-2-propanol-MWNT were combined with PP to produce hybrid films. The variations of their properties with the matrix polymer F-MWNT content are discussed. Transmission electron microscopy photographs show that most of the F-MWNTs are dispersed homogeneously in the matrix polymer on the nanoscale, although some agglomerated F-MWNT particles are formed. Even composites with low F-MWNT contents (<= 3 wt %) exhibit much better thermomechanical values than pure PP. The gas permeability of the hybrids was found to decrease linearly with increases in the F-MWNT content of the PP matrix. (c) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 244-254, 2011