Investigation on the layered structure of Au nanoparticles within block copolymer particles

Abstract

Polymer/inorganic hybrid nanomaterials has been intensively studied to combine various properties which are complementary to each other. The spatial alignment is one of the critical factors determining the integrated performance of hybrid materials as well as their respective properties. Recently, using the co-assembly of polymer chains and inorganic particles induced by solvent evaporation process within emulsion droplet is of great interest due to the advantages including the tunability and simplicity. Yet the research on the ligand controlled spatial alignment of inorganic nanoparticles under three-dimensional confined block copolymer matrix was limited by the enthalpic terms. Long polymeric ligands provide distinct advantages of introducing new entropic effects to the system. Here we show the formation of hierarchically stacked gold nanoparticle layers within the polystyrene-block-poly (4-vinylpyridine) block copolymer particles by utilizing the entropic contribution of long polymeric ligand coated on the surface of Au nanoparticles in the solvent evaporative emulsion system. The gold nanoparticles preferentially incorporated into the inner PS domains, forming Au monolayers from inside out. The volume fraction of Au NPs and the diameter of the hybrid particle are two critical parameters for controlling the number of Au NP layers. Interestingly, the layered structures couldn’t be observed when the molecular weight of the PS ligands is too small, which emphasizes the role of entropic contribution attribute to the long polymeric ligands.