Supercritical carbon dioxide as reaction medium: synthesis, catalytic properties and recovery of hybrids of amphiphilic macromolecules with metal nanoparticles
Zusammenfassung der Projektergebnisse
The preparation of metal nanoparticles in dense carbon dioxide was studied. With the aim of providing nanoscale reaction compartments for particle synthesis and stabilization, polymers with a highly branched polar amine core and C02-philic peripheries were studied. In view of providing viably accessible systems, a hyperbranched poly(ethylene imine) (PEI) scaffold was utilized. Selective amidation of the primary amine endgroups by carbonyl diimidazoleactivated carboxylic acids afforded a covalently bound C02-philic periphery. Perfluoroalkyl-, perfluorooligoether- and polysiloxane-substituted hyperbranched PEI are soluble in dense CO2; the latter remarkably also at low C02-densities. The formation of palladium and silver nanoparticles from molecular precursors by the anticipated concept, particle formation in the C02-soluble macromolecules as nanoscale reaction compartments, yield undefined particles with a very broad size distribution. Surprisingly, however, the generation of particles under conditions where the polymer is not soluble yields defined metal nanoparticles, as studied by HRTEM, XRD and XPS. While the polymer is not soluble under these conditions, swelling of the C02-philic periphery appears essential for the metal precursor to be solubilized by the dendritic polyamine core. The randomly branched PEI yielded essentially the same results as comparative experiments with a perfectly branched C02-philic substituted poly(propylene imine) dendrimer. This method appears to be quite general and convenient for the preparation of dry metal powders, which are redisperable in organic solvents. The resulting particles are active and sufficiently stable in olefin hydrogenation as a model reaction.
Projektbezogene Publikationen (Auswahl)
- Dendritic Core-Shell Molecules Soluble in Supercritical Carbon Dioxide. Macromolecules 2006, 39, 3978 - 3979
V. Martinez, S. Mecking, T. Taissing, M. Besnard, S. Moisan, F. Cansell, C. Aymonier
- A General Approach for the Synthesis of Organic-Inorganic Hybrid Nanoparticles Mediated by Supercritical CO2. J. Am. Chem. Soc. 2007, 129, 10602 - 10606
S. Moisan, V. Martinez, P. Weisbecker, F. Cansell, S. Mecking, C. Aymonier
- Synthesis of particles in dendritic structures in supercritical fluid environments. FR 2895289 Bl, August 21, 2009. Applicant: Centre National de la Recherche Scientifique
C. G. J. Aymonier, F. P. M. Cansell, S. Mecking, S. N. Moisan, V. Martinez
