Hierarchical Approach for Controlled Assembly of Branched Nanostructures from One Polymer Compound by Engineering Crystalline Domains

The interplay of crystalline packing, which governs atomic length-scale order, and hierarchical assembly, which governs longer length scales, is essential to fabricate complex superstructures from polymers for many applications. Here, we demonstrate that a diblock copolymer containing an N-octylglycine peptoid block, which has a propensity to crystallize, can form distinct hierarchical superstructures including a star-like morphology, a superbrush, or a nanosheet by tuning the balance between surface energy arising from the solubility of the copolymers and crystallization energy of the solvophobic polypeptoid blocks. We show that partially ordered micellar aggregates (clusters) are key intermediates that form early in the assembly process and template the formation of superstructures via the oriented fusion of individual micelles as the growth materials. Notably, the fiber-like branch of the superstructures is driven by crystallization and exhibits growth in a living linear manner. The superstructures can be internalized by mammalian cells and hold promise for biomedical applications.