Formation and Stabilization in Water of Metal Nanoparticles by a Hyperbranched Polymer Chemically Analogous to PAMAM Dendrimers

Abstract

Successful one-pot preparation of a hyperbranched polymer chemically analogous to PAMAM dendrimers was achieved and its use for metal nanocluster stabilization is reported. When compared to PAMAM, such experiments demonstrate clearly the effect of the macromolecular architecture on the formation of the inorganic nanoparticles.Small metal particles have quite unique optical, electronic, and catalytic properties that result from size, shape, and size distribution effects.The preparation of such metal colloids requires the use of stabilizers which prevent the thermodynamically favored aggregation of the nanoparticles in solution. Various well-known compounds (e.g., water-soluble polymers, surfactants, etc.) have been employed as stabilizers. 1 Dendrimers have also been used as nanoreactors in which metal cations are localized before reduction leading to stabilized metal nanoparticles of a few nanometers, 2 this small size being presumably related to the unique structure of the dendrimers. However, the costly synthesis of dendrimers is prohibitive for many applications. In contrast to those perfectly branched monodisperse dendrimers, randomly branched (i.e., hyperbranched) polymers can be easily accessible 3 and they can effectively stabilize metal nanoparticles in organic solvents. 4 To our knowledge, no attempt has been made, up to now, to compare nanoparticles obtained from reduction of metal salts complexed with dendrimer and hyperbranched polymer.In this work, we present the synthesis and characterization of a hyperbranched polymer that is chemically analogous and close in molecular weight to the 4th generation of PAMAM dendrimers (noted PAMAM4). Because of this similarity in the molecular weights, this hyperbranched polymer was noted HYPAM4. Characterization of gold nanoparticles prepared using these polymers is also described.Polymer Synthesis 5 and Characterization. The synthesis of hyperbranched polyamidoamines with a structure similar to the one of PAMAM dendrimers was based on a method described by Dvornic, 6 where a hexaester was reacted with a triamine (Figure 1). This method has the strong advantage of leading to hyperbranched architectures in a single step and can be carried out in large quantities. By adjusting the mole ratio between the hexaester and the triamine for the polymer synthesis, control of the final molar mass of the hyperbranched polymer can be experimentally achieved. We have focused our work on the samples obtained when a triamine/hexaester mixture of 10:1 ratio was used for the synthesis. Clearly, the characterization of this polymer demonstrates that HYPAM4 is quite comparable to the highly used PAMAM dendrimer of the 4th generation. Molar masses are very close for both compounds, as are the numbers of primary and tertiary amines (see Table 1) (by construction, HYPAM4 has, however, less amide functions when compared to PAMAM4). Indeed, to check the chemistry of the hyperbranched polymer, the quantification of amine groups was carried out by several methods. The most reliable results ...

Hyperbranched Acrylate Copolymer via Initiator‐Fragment Incorporation Radical Copolymerization of Divinylbenzene and Ethyl Acrylate: Synthesis, Characterization, Hydrolysis, Dye‐Solubilization, Ag Particle‐Stabilization, and Porous Film Formation

“…[35][36][37][38][39][40][41][42][43] The copolymer formed at 80 8C for 120 min (run 17 in Table 1) was subjected to stabilization of Ag nanoparticles. AgNO 3 was reduced with NaBH 4 at room temperature in the presence of the copolymer, and then the Ag particles containing-copolymer was isolated.…”

“…Therefore, the Ag particles are considered to be stabilized not by encapsulating in the inner void of the hyperbranched copolymer, [36][37][38][39] but by attaching multiple copolymer molecules to one Ag particle. [40][41][42][43] Scheme 1. Structure of the hyperbranched acrylate copolymer.…”

Hyperbranched polyamidoamine as stabilizer for catalytically active nanoparticles in water

“…In previous articles, we have reported the preparation and stabilization in water of gold nanoparticles in the presence of dendritic core-shell architectures based on hyperbranched poly(ethylenimine) (PEI) [21,22] or hyperbranched poly(amidoamine) chemically analogous to PAMAM dendrimers called HYPAM [23,24]. Here, we present the synthesis and characterization of platinum nanoparticles stabilized by HYPAM and demonstrate that these easily accessible composite materials are suitable for use as a reusable homogeneous hydrogenation catalyst.…”

“…HYPAM4 and HYPAM5 were synthesized as previously described [23,24]. Water was purified through a filter and ion-exchange resin (resistivity = 16 M ), using a Purite device.…”

Synthesis of calcium carbonate particles with carboxylic-terminated hyperbranched poly(amidoamine) and their surface modification

“…The particles obtained by the addition of 0.1 and 1 mg ml -1 of PAAM consisted of 10.3 wt% and 11.1 % of PAAM, respectively, and no detectable weight loss was observed at 450 1C. 20 The precursor solution was gradually added to a dispersion of CaCO 3 particles obtained by the 72 h complexation. After the dispersion was stirred overnight at room temperature, the resulting products were isolated as red-colored precursor CaCO 3 particles, of which vaterite was the primary crystalline phase, as determined by FT-IR analysis.…”