Entropy-Driven Assembly Behavior of Polymer-Grafted Nanoparticles in 3D Confined Block Copolymers

Generating organic/inorganic hybrid materials with well-defined morphologies is of great importance as spatial alignments highly affect the integrated properties of hybrid nanomaterials. Herein, we investigated the assemblies of polystyrene-grafted Au nanoparticles (Au@PS) within onion-like polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) particles depending on four parameters: 1) molecular weight (M_n) of PS ligands (N), 2) core size of Au@PS (r), 3) grafting density of PS ligands (σ), and 4) M_n of PS-b-P4VP matrix (P). Change in any of these parameters drives dramatic morphological transitions of BCP/Au@PS hybrid particles. Au@PS 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 effects of four parameters were concluded in two aspects: N, r, and σ affect the penetrability directed by the ligand architecture of Au@PS whereas P/N determines the swelling behavior of polymer blends. In addition, we introduced the “effective softness (λ_eff)” model to integrate the effects of N, r, and σ on the penetrability of Au@PS.