Thermoswitchable Janus Gold Nanoparticles with Stimuli-Responsive\nHydrophilic Polymer Brushes

Abstract

Well-defined\nthermoswitchable Janus gold nanoparticles with stimuli-responsive\nhydrophilic polymer brushes were fabricated by combining ligand exchange\nreactions and the Langmuir technique. Stimuli-responsive polydi­(ethylene\nglycol) methyl ether methacrylate was prepared by addition–fragmentation\nchain-transfer polymerization. The polymer brushes were then anchored\nonto the nanoparticle surface by interfacial ligand exchange reactions\nwith hexanethiolate-protected gold nanoparticles, leading to the formation\nof a hydrophilic (polymer) hemisphere and a hydrophobic (hexanethiolate)\none. The resulting Janus nanoparticles showed temperature-switchable\nwettability, hydrophobicity at high temperatures, and hydrophilicity\nat low temperatures, due to thermally induced conformational transition\nof the polymer ligands. The results further highlight the importance\nof interfacial engineering in the deliberate functionalization of\nnanoparticle materials.