Abstract. Palladium (Pd) nanoparticles were incorporated into an isotactic polystyrene (iPS) by a one-step drying process through simultaneous vaporization, absorption and reduction processes of palladium(II) bis(acetylacetonate), Pd(acac)2 at 180 o C for 30 min. Pd nanoparticles were observed by a transmission electron microscope (TEM), and it was found that metallic nanoparticles were selectively loaded on the amorphous region between the lamellae of iPS. The effect of Pd nanoparticles on the thermal degradation kinetics of iPS was studied by Flynn & Wall equation using thermogravimetric analyzer (TGA) data at various heating rates. The activation energy of neat iPS was ca. 130~204 kJ/mol over the thermal degradation fraction of 0.05~0.40 while that of iPS/Pd nanocomposite was ca. 221~234 kJ/mol over the same range. These meant Pd nanoparticles have positive effect on the thermal degradation of alkyl polymer chains in iPS. IntroductionPolymer nanocomposites with metallic nanoparticles have unusual properties in mechanical, thermal and catalytic applications therefore they could be used as new advanced functional materials [1][2][3]. Preparation methods for polymer/metal nanocomposites are divided into five groups: (1) metallic precursor solved in a polymer solution is reduced to metallic nanoparticles by adding reducing agent; (2) metallic precursor solved in a monomer is thermally reduced during the polymerization at high temperature; (3) colloidal metallic nanoparticles are mixed with a polymer solution; (4) impregnated metallic precursor into a polymer matrix in a solvent and then treated by a reducing agent or by thermolysis process; and (5) sublimed metallic precursor molecules penetrate into a polymer matrix and are reduced to self-assembled metallic nanoparticles [4][5][6][7]. The methods (1)-(4) are wet processes, while the last method (5) is a dry process.In this study, Pd metallic nanoparticles were incorporated into isotactic polystyrene (iPS) via the above method (5) and the effect of Pd nanoparticles on the thermal degradation kinetics of iPS was studied by Flynn & Wall equation [8,9]: