Star-shaped block copolymer stabilized palladium nanoparticles for efficient catalytic Heck cross-coupling reactions
-
Meier, Michael; Filali, Mariam; Gohy, Jean-Francois; Schubert, Ulrich S.
- Abstract:
- Palladium nanoparticles of improved stability against aggregation were prepared using 5-arm
star-shaped block copolymers with a poly(ethylene oxide) (PEO) core and a poly(e-caprolactone)
(PCL) corona as templates. The PEO core of these star-shaped block copolymers could be swollen
with palladium acetate (Pd(OAc)2) in N,N-dimethylformamide (DMF), and Pd nanoparticles
were obtained by reduction with NaBH4. This procedure resulted in well defined Pd nanoparticles
that were stabilized against aggregation due to a barrier of PCL chains. Transmission electron
microscopy (TEM) experiments strongly suggested that one Pd nanoparticle was formed inside
each star-shaped block copolymer. The stability of the Pd nanoparticles with respect to
aggregation was strongly dependent on the length of the PCL chains. Subsequently, these
nanoparticles were evaluated for their capability to act as catalysts in Heck coupling reactions.
These reactions were performed in an automated synthesizer and monitored by GC–MS revealing
that these particles are highly active for the catalytic reactions mentioned. Up to 99% conversion
was observed for the coupling of styrene with 4-bromoacetophenone within 24 h at a catalyst
loading of 0.1 mol%.
- Year:
- 2006
- Type of Publication:
- Article
- Journal:
- Journal of Materials Chemistry
- Volume:
- 16
- Pages:
- 3001 - 3006