Influence of polystyrene ligand length on the spatial arrangement of quantum dots within PS-b-PEO micelles

The spatial arrangement of functional inorganic nanoparticles within polymer micelles is essential to the nanocomposite performances. Polystyrene (PS) of different lengths (PS 24 , PS 91 and PS 163 ) are grafted onto the surface of fluorescent CdSe/CdS core/shell quantum dots (QDs) through ligand exchange procedure, and their grafting density decreases from 2.80 to 0.54, 0.18 chains/nm 2 with increase of PS ligand length. Under two competing effects, i.e. wettability between QDs and block copolymer PS 120 - b -PEO 318 and the attraction between QDs, the precise location of PS-capped QDs inside the co-assemblies can be regulated by the length of PS ligands. The low grafting density of PS 163 on the QD surface cannot overcome the van der Waals and hydrophobic attraction between QDs and cause the local aggregation of QDs within the co-assemblies. On the contrary, short PS 24 ligands with high grafting density can avoid QD aggregation, but exhibit poor wettability with copolymer, which confines the QDs in the central portion of the core of co-assemblies. PS 91 ligands with medium grafting density have good wettability with block copolymer and facilitate the homogeneous distribution of QDs inside the cores of co-assemblies. Furthermore, the influence of stirring time and water addition rate on the structure of co-assemblies is also investigated.