Control over Aspect Ratio and Polymer Spatial Distribution of 2D Platelets via Living Crystallization-Driven Self-Assembly

The aspect ratios of nano- and micrometer-sized features in nature have evolved to enable specific characteristics that are finely tuned for optimizing strength, surface area, optics, and heat dissipation. Despite the importance of aspect ratios, precise control over the aspect ratios of anisotropic polymeric nanoparticles is challenging to achieve and the formation mechanisms by which they occur are not fully understood. In this study, using the crystallization-driven self-assembly (CDSA) process, we achieved two-dimensional (2D) platelets with precisely controlled aspect ratios through the rational compositional adjustment of various polycaprolactone (PCL)-based homopolymers (HP) and block copolymers (BCP). These polymer compositions exhibit distinct polymer crystallization rates, which allow for highly controlled aspect ratios and polymer spatial distribution in 2D platelets. Brownian dynamics (BD) simulations provided an in-depth understanding of the formation of 2D platelets. The BD simulations help us further confirm the nature of living epitaxial growth, simulate the structural order of polymer chains during the CDSA process, and demonstrate the influence of PCL length on the aspect ratio. Our work opens up new possibilities for a nuanced understanding of the interplay between polymer composition, crystallization rate, and morphology, providing a method for the controlled synthesis of 2D nanostructures.