Thermoreversible Surface Polymer Patches: A CryogenicTransmission Electron Microscopy Investigation

Hybrid core−shell type nanoparticles fromgold nanoparticle cores and poly(N-isopropylacrylamide)shells were investigated with regard to their structuralplasticity. Reversible addition−fragmentation chain transferpolymerization was used to synthesize well-defined polymersthat can be readily anchored onto the gold nanoparticlesurface. The polymer shell morphologies were directlyvisualized in their native solution state at high resolution bycryogenic transmission electron microscopy, and the microscopicresults were further corroborated by dynamic lightscattering. Different environmental conditions and brusharchitectures are covered by our experiments, which leads todistinct thermally induced responses. These responses includeconstrained dewetting of the nanoparticle surface at temperatures above the lower critical solution temperature of poly(Nisopropylacrylamide),leading to surface polymer patches. This effect provides a novel approach toward breaking the symmetryof nanoparticle interactions, and we show first evidence for its impact on the formation of colloidal superstructures.