Preparation Of Palladium Nanoparticles/polymer Microspheres And Their Catalytic Property

Poly(N-vinylacetamide) (PNVA) macromonomer which has a styrol end group was synthesized by degenetative transfer polymerization and end capping reaction, respectively. The structure of PNVA was characterized by Fourier transform infrared spectroscopy (FT-IR), UltraViolet-Visible absorption spectrometry (UV-vis) and proton nuclear magnetic resonance (~1H-NMR). The results of these characterization showed that the double linkage was introduced successfully to the end group of PNVA which had a intake yield about 70%.The PNVA grafted polyacrylonitrile/polystyrene (PNVA-g-PAN/PSt) microspheres were prepared by dispersion copolymerization of acrylonitrile (AN) with styrene (St) in ethanol/water mixed solvents using PNVA macromonomer as reaction stabilizer. It can be known that the structure of PNVA-g-PAN/PSt microspheres was accordance with the expected design from the results of FT-IR and ~1H-NMR. The microspheres were well dispersed and had regular morphology, unusual morphologic and uniform diameter which can be known from the characterization of scanning electron microscopy (SEM). The images of SEM indicated that: the diameter of microspheres decreased with increasing the molar fraction of PNVA. The diameter range of microspheres was about 500-1000 nm. The volume ratio of ethanol to water had a effect on the stabilization of microspheres. Microspheres with better morphology were obtained when the volume ratio of ethanol to water was less than 7/3. The surface morphology of microspheres was weaken with increasing the proportioning of St/AN.Use the microspheres as the matrix, palladium nanoparticles were located onto the surfaces of microspheres in ethanol/water mixed solvents by in-situ reduction method using PdCl2 as metal source and ethanol as reducing agent at 90℃. The pt@pd nanoparticles were prepared by the same method. The size of palladium nanoparticles and pt@pd nanoparticles was observed by transmission electron microscopy (TEM). The results demonstrated that the palladium nanoparticles and pt@pd nanoparticles were dispersed evenly on the surfaces of microspheres. The average size was about 9 nm, 9-22 nm respectively, which was consistence with the results of X-ray diffraction (XRD). The weight percent of palladium nanoparticles was about 15 to 30% based on the characterization of thermogravimetric analysis (TG).The preliminary study showed that as-prepared loaded palladium nanoparticles can catalyze the oxidizing of glucose and have high activity. The catalytic activity of this loaded palladium nanoparticles and pt@pd nanoparticles for the cross-coupling reaction of iodobenzene with acrylic acid was good. Furthermore, the yield of products was above 90%. Besides that, the loaded palladium nanoparticles could be easily recovered and reused, which remained high catalytic activity after reused 5 times. Moreover, the yield of Heck reduction products was still 88%.