Structural flexibility dominates over binding strength for supramolecular crystallinity

Supramolecular crystallinity is abundantly present in nature and results from directional, weak non-covalent interactions between components. Bottom-up nanotechnology aims to exploit such phenomena to control the self-assembly of ordered networks and complex objects from rationally designed monomers. Like all crystalline materials, 2D supramolecular crystals develop from an initial nucleation site, followed by growth, based on directional interactions. Traditionally, the binding strength and directionality of interactions is thought to dictate the nucleation and crystal growth, whereas structural flexibility favours defects. Usually, macromonomers present multiple binding units with relative intramolecular flexibility that affects their intermolecular interactions. Thus far, the effects of such flexibility on supramolecular assembly have not been explored. Here we introduce the concept of "interface flexibility" and demonstrate its critical importance in the nucleation and growth of supramolecular crystalline networks. We show that tuning the interface flexibility greatly expands the available design space for synthetic supramolecular crystalline materials.