Block Copolymer Micelles as Nanoreactors for Self-Assembled Morphologies of Gold Nanoparticles (original) (raw)
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Block copolymer micelles as nanoreactors for single-site polymerization catalysts
Journal of Polymer Science Part A: Polymer Chemistry, 2009
New micelle-like organic supports for single site catalysts based on the self-assembly of polystyrene-b-poly(4-vinylbenzoic acid) block copolymers have been designed. These block copolymers were synthesized by sequential atom transfer radical polymerization (ATRP) of styrene and methyl 4-vinylbenzoate, followed by hydrolysis. As evidenced by dynamic light scattering, self-assembly in toluene that is a selective solvent of polystyrene, induced the formation of micelle-like nanoparticles composed of a poly(4-vinylbenzoic acid) core and a polystyrene corona. Further addition of trimethylaluminium (TMA) afforded in situ MAO-like species by diffusion of TMA into the core of the micelles and its subsequent reaction with the benzoic acid groups. Such reactive micelles then served as nanoreactors, MAO-like species being efficient activators of 2,6-bis[1-{(2,6-diisopropylphenyl)imino}ethyl]pyridinyl iron toward ethylene polymerization. These new micelle-like organic supports enabled the production of polyethylene beads with a spherical morphology and a high bulk density through homogeneous-like catalysis.
ACS applied materials & interfaces, 2017
Original porous catalytic supports can be engineered via an effective and straightforward synthetic route to polystyrene-block-poly(d,l-lactide) diblock copolymer precursors displaying an acid-cleavable acetal junction between both blocks. To this purpose, we synthesized an acetal-containing heterodifunctional initiator, thus enabling to combine two different polymerization methods, i.e., first atom transfer radical polymerization (ATRP) of styrene, and then ring-opening polymerization (ROP) of d,l-lactide. Thanks to the labile nature of the acetal junction, oriented porous frameworks could be obtained upon trifluoroacetic acid-mediated cleavage of the latter, after orientation of the block copolymer nanodomains by solvent vapor annealing. The resulting porous materials bearing a reactive aldehyde function at the pore surface allowed for further chemical modification via reductive amination with amino-containing compounds, such as tetraethylenepentamine, thus leading to amine-functi...
Polymer Micelles as Supports for the Production of Millimetric Polyethylene Beads
Macromolecules, 2008
The self-assembly in toluene of linear polystyrene functionalized in R-position by benzoic acid moieties into active micelle-like structures was exploited to trap trimethylaluminium and thus generate encapsulated methylaluminoxane-like species. These nanomicellar reactors were subsequently used as such or in the presence of free benzoic acid for supporting the tridentate bis(imino)pyridinyl iron catalyst for ethylene polymerization. In this way, high catalytic activities and polyethylenes (PEs) with unimodal chain distribution and controlled morphology were obtained. Remarkably well-defined spherical PE beads with an average diameter of 2 mm were produced when free benzoic acid was added to the micellar polymeric supports.
Macromolecular Chemistry and Physics, 2012
A new approach is developed for the preparation of nanoporous gold (Au) fi lms using diblock copolymer micelles as templates. Stable Au nanoparticles (NPs) with a narrow distribution are prepared by modifying NPs functionalized with 4-(dimethylamino)pyridine ligands (DMAP Au NPs) and a spherical micelle formed through the epoxidation of poly(styrene-b-butadiene) diblock copolymer to produce poly(styrene-b-vinyl oxirane) (PS-b-PBO) in tetrahydrofuranacetonitrile solution. The exchange reaction of 4-aminothiophenol of PS-b-PBO diblock copolymer micelles with DMAP Au NPs can produce block copolymer-Au NPs composite fi lms. After the pyrolysis of the diblock copolymer templates at a specifi c temperature to avoid the collapse of the Au NPs, a nanoporous Au fi lm is prepared.
Triblock copolymer-mediated synthesis of catalytically active gold nanostructures
Journal of Nanoparticle Research, 2018
The design of nanostructures based on poly(ethylene oxide)-poly(propylene)-poly(ethylene oxide) (PEO-PPO-PEO) and metal nanoparticles is becoming an important research topic due to their multiple functionalities in different fields, including nanomedicine and catalysis. In this work, water-soluble gold nanoparticles have been prepared through a green aqueous synthesis method using Pluronic F127 as both reducing and stabilizing agents. The size dependence (varying from 2 to 70 nm) and stability of gold nanoparticles were systematically studied by varying some parameters of synthesis, which were the polymer concentration, temperature, and exposure to UV-A light, being monitored by UV-Vis spectroscopy and TEM. Also, an elaborated study regarding to the kinetic of formation (nucleation and growth) was presented. Finally, the asprepared Pluronic-capped gold nanoparticles have shown excellent catalytic activity towards the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride, in which a higher catalytic performance was exhibited when compared with gold nanoparticles prepared by classical reduction method using sodium citrate.