Stabilization of gold nanoparticles by polymers prepared by the
RAFT process
The use of
polymers has been considered as a valuable approach for the
synthesis of gold nanoparticles since polymers can act as reducing
and/or stabilizing agents. Gold nanoparticles have for example been
prepared in one step by mixing a gold precursor, a reducing agent,
and a polymer made by Reversible Addition-Fragmentation Chain
Transfer (RAFT) polymerization. By virtue of the polymerization
mechanism this polymer bears a dithioester moiety at one end of the
chain. When the three components are mixed together the reducing
agent turns the gold salt into metallic gold, and reduces at the
same time the dithioester into thiol which chemisorb onto the
nanoparticles, stabilizing them.
We have demonstrated that hybrid gold nanoparticles synthesized in
a five-arm PEG-b-PCL star-block copolymer, and thus containing
hydrophobic PCL stabilizing chains, could be turned into
hydrophilic particles by grafting a new corona in a one step
approach using poly(acrylic acid) (PAA) containing a
trithiocarbonate group, without further reduction of the
trithiocarbonate group. The chemisorption of the trithiocarbonate
group onto model gold surfaces was confirmed by XPS and AFM-based
force spectroscopy measurements. Such functional group is easily
introduced in macromolecular chains by a RAFT polymerization
process, and can chemisorb onto gold. The modified hybrid gold
nanoparticles were successfully transferred into water at pH = 9.
The presence of trithiocarbonate group is mandatory since the
transfer process failed when non-functional PAA was
used.
Schematic
representation of the chemisorption of trithiocarbonate-containing
PAA onto gold nanoparticles templated in a five arm PEO-b-PCL star
copolymer.
Researchers involved: Catheline
Colard, Mariam Filali
Collaborations:
Ulrich Schubert
(Eindhoven), Michael Meier (Eindhoven), Anne-Sophie Duwez
(ULg)
Relevant
papers:
"Dithioesters and trithiocarbonates as anchoring groups for the
grafting-to approach"
A.-S. Duwez, P. Guillet, C. Colard, J.-F. Gohy, C.-A.
Fustin
Macromolecules
2006, 39,
2729-2731
"Tuning the hydrophilicity of gold nanoparticles templated in
star-block copolymers"
C.-A. Fustin, C. Colard, M. Filali, P. Guillet, Anne-Sophie Duwez,
M. A. R. Meier, U. S. Schubert, J.-F. Gohy
Langmuir
2006, 22,
6690-6695
"Trithiocarbonate-containing poly(acrylic acid) chains as
stabilizers for gold nanoparticles templated in star block
copolymers and in viruses"
M. Filali, C. Colard, P. Guillet, C.-A. Fustin, P. Soumillion, M.
A. R. Meier, U. S. Schubert, J.-F. Gohy
Polymer
Preprints
2006, 47,
961-962