RAFT-Polymers with Single and Multiple Trithiocarbonate Groups as Uniform Gold-Nanoparticle Coatings

The nanostructures of nanohybrids with gold-nanocrystal cores and shells of N-isopropylacrylamide polymers containing single or multiple trithiocarbonate (TTC) groups were analyzed in detail. The polymers were synthesized in RAFT polymerizations and then grafted to gold nanoparticles (similar to 14 nm) from citrate reduction. Analysis via TEM revealed self-assembled hexagonal lattices of gold cores. The interparticle distances increased, when polymers with single TTC end groups and growing molar masses were employed as coating agents, allowing for a reference curve to be found. When using polymers containing multiple TTC groups along their backbone for the surface modification, the spacings between the gold cores were unexpectedly low and remained constant, independent of the polymers' chain lengths and the number of trithiocarbonate groups, which shows-backed up by results from size-exclusion chromatography-that these macromolecules are wrapped around the gold nanoparticles with several gold-TTC junctions. Absolutely no cross-linking was observed for these novel and promising nanohybrids.