Solution Structure of Metal Particles Prepared in Unimolecular Reactors of Amphiphilic Hyperbranched Macromolecules

The structure of metal nanoparticles templated by amphiphilic hyperbranched polyethylenimine-amides in apolar organic solution was studied by means of small-angle neutron scattering (SANS). SANS measurements at different concentrations revealed that the neat polymer is present as nonaggregated unimolecular micelles for a polymer with M_w 3.9 × 10⁴ g mol^-1 and that silver particles are stabilized by a single polymer molecule. For a polymer of M_w 1.2 × 10⁴ g mol^-1, some aggregation occurs upon loading with the silver salt (AgNO₃) and particle formation. Contrast variation experiments were performed employing different compositions of C₆D₆ and C₆H₆ in the solvent mixture. For the larger molar mass polymer a homogeneous distribution is found for the polymer/metal particle hybrides, whereas for the lower molecular weight polymer the metal particles are off-center.