Preparation of Poly(N-isopropylacrylamide)-Monolayer-Protected Gold Clusters: Synthesis Methods, Core Size, and Thickness of Monolayer

Abstract

The preparation of poly(N-isopropylacrylamide)-monolayer-protected clusters (PNIPAM-MPC) of gold nanoparticles was carried out in a homogeneous phase using three methods, in which three types of PNIPAM ligands were employed. The first type was comprised of PNIPAMs with narrow molar mass distributions, synthesized by reversible addition−fragmentation chain transfer (RAFT) polymerization and thus bearing a dithiobenzoate at the chain end. These polymers were used directly to passivate the gold nanoparticles upon the Schiffrin reaction in a one-pot synthesis. The second type of ligand was derived from the first one through hydrazinolysis, and they therefore contained a thiol end group. The third type of ligand was PNIPAMs obtained through conventional radical polymerization, postmodified to contain thiol end groups. The PNIPAM-MPCs were characterized by high-resolution transmission electron microscopy, UV−vis spectroscopy, and dynamic light scattering. The one-pot synthesis utilizing the ligands of the first...