Nanoassemblies formed from hydrophilic block copolymers and multivalent ions

Abstract

We recently reported on the controlled formation of highly stable metal hydroxide nanoparticles. Growth control and stabilization of particles were achieved by performing hydrolysis and polycondensation reactions of polymer-complexed metal cations, the polymers being double hydrophilic block copolymers (DHBCs). The present paper focuses on the characterization of the intermediate species in the formation process, namely the mixture of multivalent metal cations plus the oppositely charged polyelectrolyte–neutral block copolymers. Complexation of metal cations by the anionic block of the DHBCs leads to the spontaneous formation of colloidal objects. Small angle neutron scattering experiments show that the aggregates exhibit a well defined core–corona architecture: the core is compact and homogeneous while the diffuse corona is constituted of polymer segments in a good solvent. The core formation is due to the water insoluble metal cation–polyacrylate complex while the corona is constituted of the water soluble neutral polymer blocks. Cryo-TEM images allowed the revelation of well-dispersed inorganic-rich domains. The presence of the longer neutral blocks prevents macroscopic phase separation of the complex and leads to the formation of hybrid micellar aggregates.