The Preparation And Application Of Au-Polymer Hybrid Microgels

As one of the most widely studied inorganic materials, gold nanoparticles (GNPs) have shown diverse applications in catalysis, sensors and biomedicines, etc. However, because of their high surface energy, GNPs tend to coagulate when some environmental factors (such as pH, solvent and ionic strength) change, which seriously affects their performance. Polymer microgels are good matrix for stabilizing GNPs, while the preparation of Au-polymer hybrid microgels are usually complex. Our research forcus on developing facile methods for preparing Au-polymer hybrid microgels, and the primary results are listed as follows:1. A new thermo-responsive copolymer, P(MEO2MA-co-OEGMA-co-TMSPMA) was synthesized via RAFT polymerization. This polymer can anchor onto the surface of GNPs through the exchange between RAFT end groups and the citrates, endowing GNPs thermo-responsiveness. When the mixture of P(MEO2MA-co-OEGMA-co-TMSPMA) and the GNP solution are heated above the lower critical solution temperature (LCST) of the polymer, both the unbound polymer chains and GNPs turn hydrophobic and they co-aggregate into hybrid nanoparticles. Owing to the existence of TMSPMA units in the polymer chains, these particles can be gradually crosslinked by the hydrolysis-condensation reaction of methoxysilyl groups, forming hybrid microgels ultimately. This method for preparing Au-polymer hybrid microgels is quite simple, because no preforming of microgels or modification of GNPs is needed. The size of the microgels can be easily adjusted by varying the polymer concentration. Further more, products with different volume phase transition temperatures (VPTT) can be easily obtained by using P(MEO2MA-co-OEGMA-co-TMSPMA) of different monomer ratios.2. A new thermo-responsive copolymer, P(DMAEMA-co-TMSPMA) was synthesized via RAFT polymerization. This polymer can form microgels through a temperature-induced self-aggregation and self-crosslinking process upon heating the aqueous solution above the LCST. When HAuCl4 is added into the hydrothermal suspension of the microgels, Au3+ can be trapped and quickly reduced by DMAEMA units, forming Au-polymer hybrid microgels. This method for preparing Au-polymer hybrid microgels has following advantages. Firstly, the preparation of polymer microgels is quite simple, needing no any additive such surfactant or crosslinking agent. Secondly, the obtained polymer microgels can be directly used in the reduction of Au3+, needing no purification. Thirdly, Au3+ is directly reduced by microgels, needing no additive reducing agent. The whole process from preparing polymer microgels to forming hybrid microgels can be completed within 1 h. In addition, the content of GNPs in microgels can be easily adjusted by varying the adding amount of HAuCl4.