Hierarchical self-assembly of fluorine-containing diblock copolymer:From onion-like nanospheres to superstructured microspheres

Superstructured microspheres were prepared via a two-tier hierarchical assembly of a fluorine-containing diblock copolymer, poly(tert-butyl acrylate)-b-poly(2-[(perfluorononenyl)oxy]ethyl methacrylate) (PtBA-b-PFNEMA) with well controlled block lengths. At tier 1, water induced self-assembly of the diblock copolymer produced nanospheres of low dispersity with onion-like multilayer inside structures, which were the consequence of the gradual aggregation of the fluorinated segments by accessing the super-strong segregation regime. And both the size and inner structure could be tuned by changing the water addition rate. At tier 2, nanospheres with different sizes were chosen as the building blocks for the formation of closely packed superstructural microspheres through an evaporation assisted process. The packing rules were governed by the volatility distinction between THF and water, the dispersity of nanospheres, and other various forces, such as the capillary force.