Lateral Growth of Hexagonal Platelet Micelles via Crystallization by Particle Attachment

Two-dimensional (2D) platelets with highly symmetric structure and low dispersity in size have attracted great attention due to their unique planar structure with high specific surface area. The living crystallization-driven self-assembly of block copolymers (BCPs) in selective solvent through seeded growth approach enables the formation of well-defined 2D platelets with excellent uniformity, which is generally considered via the epitaxial crystallization mechanism. Herein, we demonstrate the lateral growth of hexagonal platelets using BCPs containing crystalline side chains via an alternative growth mechanism known as crystallization by particle attachment. By adding hot polymer solution to the preformed 2D platelet seeds, spherical micelles are immediately formed due to the phase transition of crystalline side chain BCP. These kinetically trapped spheres served as building motifs and were fused into the platelet edges during the aging process. The lateral growth of hexagonal platelets via crystallization by particle attachment was confirmed by morphological imaging and shows living character. Hence, the area of a hexagonal platelet could be finely manipulated by adding different masses of polymer solution to the 2D platelet seeds. Moreover, we reveal that the core length and crystallographic d spacing of the side chain length are both strictly required for the successful lateral growth of platelets via crystallization by particle attachment.