Building block copolymer particles via self-assembly within a droplet

The self-assembly of block copolymers (BCPs) within emulsion droplets is a flexible strategy for the preparation of polymer particles. This strategy permits the fine-tuning of shapes, internal structures, and surface nanostructures of the polymer particles, thus allowing many applications. Although some literature has reviewed the BCP preparation via self-assembly within a droplet, a comprehensive summary including in-depth understanding, controllable preparation, and application is lacked. In this review, we systematically delve into the multiple mechanisms that drive BCP self-assembly within emulsion droplets, such as commensurability effects for minimizing total free energy, interfacial instability, organized spontaneous emulsification, phase separation of multiple components, and entropy effects between BCPs and nanoparticles. Additionally, a strategy combining selective cross-linking and disassembly can further generate Janus particles featuring unique structures. Next, various applications across multiple disciplines are discussed, including drug delivery, display, biomedical imaging, macromolecular separation, and fuel cells. Finally, we present an overview of the current challenges and future directions for BCP emulsion self-assembly, covering mechanism investigation, molecular design, stability control, and application exploration. We anticipate deeper understanding, more varieties, enhanced performance, and broader applications can be achieved with BCP emulsion self-assembly after addressing the challenge.