Metal Nanocrystals Embedded within Polymeric Nanostructures: Effect of Polymer-Metal Compound Interactions

pH-responsive PDEAEMA-b-PHEGMA amphiphilic block copolymers and random polymer networks have been used as matrices for the incorporation of metal species and the nucleation and growth of metal nanoparticles with sizes in the range of a few nanometers. The polymer characteristics and polymer-metal interactions upon metal incorporation and after metal reduction were investigated. Two different synthetic procedures were followed for the preparation of Pt nanoparticles within the block copolymers; addition of the metal precursor in a molecular copolymer solution at low pH led to a polymer-metal charge neutralization process and the formation of micelles with compact non-hydrated cores, while the incorporation of H2PtCl6 in a micellar copolymer solution at high pH led to polymer aggregation. The impregnation of K2PtCl6 in a micellar copolymer solution at high pH was unsuccessful suggesting the lack of coordination of the neutral amine groups to the metal precursor. The effect of the metal precursor impregnation and the metal nanoparticle formation on the degree of swelling of random networks carrying different functionalities was also examined and the metal content of the hybrid materials was assessed. The equilibrium degrees of swelling of the networks were determined by two opposing effects: the degree of ionization, which caused the network to swell, and the polymer-metal complexation, which increased the effective cross-link density and caused the network to shrink. The metal content of the network was dictated by the polymer-metal interactions and the degree of swelling of the network in the solvent medium. These hybrid materials are proposed for use as advanced catalysts in the synthesis of high-value cosmetics and pharmaceuticals.