Effect of Softness of Polymer Grafted Nanoparticles on the Co-assembly Behavior in 3D Confined Nanoparticle/Block Copolymer Hybrid System

Controlling the spatial alignment of inorganic nanoparticles (NPs) within polymer matrix is of great importance due to its great potential for building novel hybrid materials. Herein, we demonstrate the precise spatial distribution tuning of softness-controlled polystyrene-grafted Au NPs (Au@PS) within polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) particles. The softness of Au NPs was controlled by changing the ratio of the PS ligand length to the inorganic core size. The hybrid particles produced via solvent-evaporative emulsions led to the formation of spherical PS-b-P4VP particles with radially-stacked lamellar morphology, while the spatial distributions of Au@PS NPs showed strong dependence on the softness of Au@PS NPs within PS-b-P4VP particles. Au@PS showing the characteristics of hard spheres were excluded from the block copolymer domains and formed well-ordered hexagonal packing on the particle surface. In stark contrast, Au@PS with the characteristics of soft spheres hierarchically stacked within the inner favorable domains and showed stronger selectivity to the domains which close to the center of onion particles. Finally, the phenomena will be explained by considering the entropic interactions between the BCP chains and PS ligands on Au surface.