Decoding the evolution and dynamics of semicrystalline block copolymer assembly via liquid-phase transmission electron microscopy

Abstract

Nature utilizes self-assembly to form complex, functional structures, inspiring advanced materials design. Polymer crystallization drives assemblies with both ordered and disordered regions. Crystallization-driven assembly of BCPs enables unique hierarchical nanostructures with enhanced colloidal stability and directionality, applicable from optoelectronics to biomedicine. However, mechanisms governing morphological transitions remain poorly understood due to complex microphase separation and competitive crystallization. Using liquid-phase transmission electron microscopy, we visualize the spontaneous assembly of semicrystalline amphiphilic BCPs. We observe structural transformations from unimers to spherical, cylindrical, toroidal micelles, and vesicles by varying constituent block ratios. Image segmentation overcomes low contrast of aqueous assemblies, enabling motion tracking. Nanostructures exhibit structural evolution driven by long-range hydrophobic interactions from formed elemental micelles undergoing anomalous diffusion. Notably, toroid formation follows a distinct pathway compared with conventional BCPs due to semicrystalline BCPs’ preference for low curvature at the core-corona interface. Insights into assembly dynamics via real-time imaging provide strategies for controlling complex hierarchical structures.