AuCl4--responsive self-assembly of ionic liquid block copolymers for obtaining composite gold nanoparticles and polymeric micelles with controlled morphologies

The double hydrophilic ionic liquid block copolymer (ILBC), poly(ethylene glycol)-block-poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)] (PEG(113)-b-PMMPImB(24)), was synthesized through RAFT polymerization of 1-methyl-3-(2-methacryloyloxy propylimidazolium bromine) using PEG-CTA as a chain transfer agent. Directly interacting with AuCl4- in aqueous solutions, the micellization of self-assembling PEG(113)-b-PMMPImB(24) was induced via the anion responsive properties of the ILBC. Then, the composites of polymeric micelle encapsulated gold nanoparticles (GNPs) were successively obtained by the reduction of AuCl4- in situ. At a lower molar ratio of AuCl4- to imidazolium, the obvious vesicle structures of the polymeric micelles with AuCl4- and the composites with GNPs were formed and the distribution of GNPs in the polymersome walls appeared to be uniform in size. The spherical micelles with highly packed GNPs were also obtained by increasing the content of AuCl4-. These results indicate that the unique chemical and physical properties of PILs in the micellar core can control the micellar morphology and the distribution of GNPs in a confined space.