Block copolymer-directed metal nanoparticle morphogenesis and organization

Advances in the nanoscale design of polymeric, "soft" materials and of metallic, "hard" materials can converge at the "interfaces" to form hybrid nanomaterials with interesting features. Novel optical, magnetic, electronic, and catalytic properties are conferred by metal nanoparticles, depending on their morphology (size and shape), surface properties, and long-range organization. We review here the utilization of block copolymers for the controlled synthesis and stabilization of metal nanoparticles. Solvated block copolymers can provide nanoscale environments of varying and tunable shape, dimensions, mobility, local polarity, concentration, and reactivity. In particular, block copolymers containing poly(ethylene oxide) can exhibit multiple functions on the basis of their organization at the intra-polymer level (i.e., crown ether-like cavities that bind and reduce metal ions), and at the supramolecular level (surface-adsorbed micelles, and ordered arrays of micelles). These block copolymers can thus initiate metal nanoparticle formation, and control the nanoparticle size and shape. The physically adsorbed block copolymers, which can be subsequently removed or exchanged with other functional ligands, stabilize the nanoparticles and can facilitate their integration into diverse processes and products. Block copolymers can be further useful in promoting long-range nanoparticle organization. Several studies have elucidated the nanoparticle synthesis and stabilization mechanism, optimized the conditions for different outcomes, extended the ranges of materials obtained and applications impacted, and generalized the scope of this functional polymer-based nanoparticle synthesis methodology.