Importance of the Polymer Ligand Conformation to the Assembly of Nanoparticles within Emulsion-Evaporative Block Copolymer Particles

The conformation of polymer brushes highly affects the interactions between ligand-grafted nanoparticles and polymer matrices, thus determining the nanostructures of hybrid materials. Herein, we demonstrated the precise spatial alignment of polystyrene-grafted Au nanoparticles (Au@PS) within onion-like polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) particles depending on the parameters related to the conformation of PS ligands, including the ratio of PS block molecular weight (M_n) to PS ligand M_n (P/N), core size of Au@PS (r), and grafting density of PS ligands (σ). Change in any of these parameters drives dramatic morphological transitions of hybrid particles. PS ligands having low interfacial interactions with BCP chains were excluded from the BCP domains and formed hexagonal packing on the particle surface. In contrast, high interfacial interactions between Au@PS and BCP chains allowed the formation of Au@PS arrays between PS blocks. The phenomena were explained by considering the ligand architecture directed-interdigitation and swelling behavior between grafted polymer and matrix polymer. In addition, the effect of nanoparticle size was also taken into account for a comprehensive understanding of the entropic interactions in a BCP-based hybrid system.