Palladium (Pd) nanoparticles were incorporated into free-standing polymer films by a one-step dry process involving simultaneous vaporization, absorption and reduction schemes of palladium(II) bis(acetylacetonate), Pd(acac)(2), used as a precursor. Matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry (MALDI-TOF MAS) and Fourier transform infrared spectroscopy (FTIR) analyses showed that the polymers maintained their molecular structures throughout the process. The metal nanoparticles were selectively loaded into the amorphous regions between the lamellae of crystalline polymers having higher melting temperatures than the processing temperature (180 degrees C). The uniformly dispersed Pd nanoparticles retarded the thermal decomposition of polystyrenes, polypropylene and a methacrylate polymer, and accelerated the thermal decomposition of polyamide 6 and poly(ethylene terephthalate), as seen from the results of thermogravimetric analysis (TGA). Kinetic studies showed that retardation of the degradation was mainly due to suppression of the mobility of polymer chains by the Pd nanoparticles, while acceleration of the degradation was mainly attributed to a decrease in the degradation activation energy due to the catalytic role of the Pd nanoparticles. (c) 2006 Elsevier Ltd. All rights reserved.