A promising route to the synthesis of protein-mimetic materials that are capable of strong mechanics and complex functions is provided by intermolecular β-sheet stacking. An understanding of the assembly mechanism on β-sheet stacking at molecular-level and the related influencing factors determine the potential to design polymorphs of such biomacromolecular materials towards broad applications. Herein, we quantitatively reveal the air/water interface (AWI) parameters regulating the transformation from crowding amorphous aggregates to ordered phase and show that the polymorph diversity of β-sheet stacking is regulated by the chain relaxation-crystallization mechanism at AWI. A macroscale amyloidlike nanofilm with an amorphous structure is formed at the AWI by phase separation, in which unfolded protein chains are aligned in a short-range manner to form randomly packed β-sheets. The subsequent biopolymer chain relaxation-crystallization to form nanocrystals is further triggered by removing the limitations of energy and space at the AWI. Notably, mesoscale assembly of biopolymer nanocrystals at the AWI is achieved by simply modulating the surface tension and surface spatial degree of freedom, and the resultant polymorphs of amyloid crystals, including edge-to-edge extending and face-to-face packing of β-sheets, are not observed in the natural world and therefore are insightful to the precise synthesis of unprecedented biomaterials.

DOI: 10.1002/anie.202008999