The Preparation Of Metal/Polymer Composite Nanoparticles

As a kind of common metal nanomaterial, silver nanoparticles(Ag NPs) have attracted extensive research interest due to its potential applications in the nanoelectronics, optical, catalytic and biological medicine and so on. In the process of the preparation of Ag NPs, the groups containing carboxyl, N atoms or S atomic are the most commonly used as capping agents for stabilizing metal NPs in solution, and the obtained NPs have good stability at room temperature in the short term. However, due to dissociation of the protecting ligands from the NPs surface, the instability of most NPs at elevated temperatures limits many of applications.So far, the metal NPs/polymer composite materials have become a research hotspot because of its advantages of the two kinds of material. On the one hand, they can keep the special properties and function of metal NPs, on the other hand, as shell material, polymer can improve the long-term stability of the NPs, regulate the solubility of NPs, improve the compatibility between NPs and polymer matrix and the processing properties etc.The main research contents and results in this paper are as follows.(1) Ag NPs and copper NPs(Cu NPs) stabilized by polymer brushes were prepared. Firstly, polystyrene(PS) with trithiocarbonate group at the middle of the chain was synthesized by the reversible addition-cracking chain transfer(RAFT) polymerization of styrene. Then triblock copolymer PS-b-PBA-b-PS was obtained by RAFT polymerization of butyl acrylate(BA) using PS as macromolecular chain transfer agent. Finally, Ag NPs and Cu NPs composite NPs were prepared by in-situ reduction using PS and PS-b-PBA-b-PS as stabilizers respectively. UV-Vis spectra(UV-Vis) and transmission electron microscope(TEM) suggested that the NPs were uniform and had good dispersion in solution. And they can be reserved for a long time at room temperature.(2) Ag NPs particles of high thermal stability were prepared using triblock copolymer PS-b-P4VP-b-PS as multidentate ligand. Firstly, PS-b-P4VP-b-PS was synthesis by RAFT polymerization of strene and 4-vinyl pyridine(4VP). Then Ag NPs were obtained by in-situ reduction of silver nitrate using PS-b-P4VP-b-PS as multidentate ligand. UV-Vis and TEM show that Ag NPs particles were spherical, and particle were uniform and had good dispersion. No aggregation or agglomeration of Ag NPs was observed after heating up to 110℃ for more than 24 h, showing good thermal stability. To further increase its thermal stability, we tried to use 1, 4-dibromobutane(DBB) to crosslink P4 VP chain segment. It was found that the Ag NPs color faded and plasma resonance absorption peak disappeared. The reason is Ag NPs of after crosslinking reaction was oxidized to Ag + and dissolved in solution. The method using DBB to crosslink P4 VP chain segment to further improve the thermal stability of nanoparticles is infeasible.(3) Ag NPs and Pd NPs composite particles were prepared by using crosslinked block copolymer micelles as template. Firstly, block copolymer PS-b-P4VP-b-PS micelles were formed in toluene. Then Ag NPs and Pd NPs were obtained using micelles as stabilizer and different reductant to reduction silver perchlorate and palladium acetate. UV-Vis and TEM show that silver composite NPs containing multiple Ag NPs in a micelle were obtained using tetrabutylammonium to reduction silver perchlorate. And the composite NPs are spherical and have good distribution. While palladium composite NPs containing one Pd NPs in a micelle were obtained using hydrazine hydrate to reduction palladium acetate. And the composite NPs are in center of micelle and have good distribution.