Poly(methyl methacrylate)/palladium nanocomposites:: Synthesis and characterization of the morphological, thermomechanical, and thermal properties

PMMA/Pd nanocomposites were prepared by means of free radical polymerization of methyl methacrylate using AIBN initiator in the presence of palladium acetate at 50 degreesC (48 h), and subsequent thermal conversion of palladium acetate into palladium metal at 120 degreesC (1 h). Morphological, thermomechanical, and thermal properties of PMMA/Pd nanocomposites were studied as a function of Pd content which was varied between 0.0001 and 0.01 vol%. According to transmission electron microscopy analyses of thin sections, the average Pd nanoparticle size increased slightly from 1.9 to 2.5 nm with increasing Pd content. Size exclusion chromatography revealed that MMA polymerization was not affected by the presence of Pd acetate. The elastic modulus and glass transition temperature, as determined by dynamic mechanical analysis, decreased from 3.4 GPa and 130 degreesC for neat PMDJA to 2.85 GPa and 122 degreesC for PMMA/Pd containing 0.01 vol% Pd. Thermogravimetric analysis showed that the presence of small amounts of Pd (0.0005-0.005 vol%) significantly improved thermal stabilities, as evidenced by a degradation initiation retarded by 75 degreesC and a gain of 32 degreesC at the maximum decomposition rate.