A Facile Preparation of Highly Thermally Stable Silver Nanoparticles Using PS-b-P4VP-b-PS Triblock Copolymer as Multidentate Ligand

Silver nanoparticles (Ag NPs) of improved thermal stability against long-term aggregation were prepared using the polystyrene-b-poly(4-vinylpyridine)-b-polystyrene (PS-b-P4VP-b-PS) triblock copolymer as a multidentate ligand. First, PS-b-P4VP-b-PS was synthesized by sequential reversible addition-fragmentation transfer (RAFT) polymerization of styrene and 4-vinylpydine using a trithiocarbonate chain transfer agent (CTA). Then Ag NPs were obtained by in situ reduction of silver nitrate using PS-b-P4VP-b-PS as a multidentate ligand. The obtained Ag NPs were stable in solution for at least 24 h while being heated at 110 degrees C. The effect of the molar ratio of N atoms of the P4VP chain segment and AgNO3 on the stability of Ag NPs was studied, and the results suggested that Ag NPs were very stable even if the molar ratio of N atoms of the P4VP chain segment and AgNO3 was very low. This method is promising to scale up the preparation of metal NPs with good dispersibility and thermal stability, which still remains challenging. To further improve its thermal stability, 1,4-dibromobutane was used to chemically crosslink the P4VP chain segment in solution. However, the results proved that the crosslink method is infeasible to further improve the thermal stability of Ag NPs in this system.