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This study reports the design of a donor‐acceptor (D‐A) molecule with two fluorene units on each side of a benzothiadiazole moiety, which allows multiple intermolecular interactions to compete with one another so as to induce the evolution of the metastable 2D platelets to the stable 2D platelets during the self‐assembly of the D‐A molecule. Importantly, the living seeded self‐assembly of metastable and stable 2D structures with precisely controlled sizes can be conveniently achieved using an appropriate supersaturated level of a solution of the D‐A molecule as the seeded growth medium that can temporarily hold the almost‐proceeding spontaneous nucleation from competing with the seeded growth. The stable 2D platelets with smaller area sizes exhibit higher sensitivity to gaseous dimethyl sulfide, illustrating that the novel living self‐assembly method provides more available functional structures with controlled sizes for practical applications. The key finding of this study is that the new living methodology is separated into two independent processes: the elaborate molecular design for various crystalline structures as seeds and the application of a supersaturated solution with appropriate levels as the growth medium to grow the uniform structures with controlled sizes; this would make convenient and possible the living seeded self‐assembly of rich 1D, 2D, and 3D architectures. [ABSTRACT FROM AUTHOR]

The controlled formation of complex and functional 1‐, 2‐, and 3D hierarchical assemblies from molecular building blocks represents a key current challenge. Herein, we report the use of a seeded growth approach for a series of perylenediimide‐based molecules (PDIs 1–4) to access otherwise inaccessible self‐assembly pathways that yield complex hierarchical structures. The key to the new approach is to use hetero‐seeds which possess a different composition and morphology from that of the molecular building block. For example, a nanotube seed (from PDI 3) and a microribbon seed (from PDI 4) were found to initiate different self‐assembly pathways for PDI 1, which normally assembles to yield nanocoils. This led to the formation of unprecedented 3D scroll‐like and scarf‐like hierarchical nanostructures, respectively. Also, the hetero‐seeds from PDI 3 initiate hidden self‐assembly pathways of PDI 2 to generate 1D tubular heterojunctions. Significantly, this new strategy offers new opportunities to create emergent and functional hierarchical and complex structures from small molecule precursors. [ABSTRACT FROM AUTHOR]