Disk-shaped nanoparticle aggregates organized in a hierarchical structure in a microphase separated block copolymer were prepared in a two-step process. First, a system comprising of polystyrene-block-poly(2-vinyl pyridine) and a palladium-pincer based surfactant was let to thermally equilibrate, resulting in the formation of structured material with hierarchically distributed concentrations of the palladium precursors. Then, in-situ reduction of the palladium precursors yielded the hierarchically organized nanocomposite. The importance of using an amphiphilic molecule for obtaining the hierarchical arrangement of the nanoparticle aggregates is demonstrated. Hierarchically arranged nanocomposites consisting of shape-controlled nanoparticle aggregates can potentially be useful as photonic materials with unique anisotropic optical response. (C) 2015 Elsevier Ltd. All rights reserved.