Shear Force Cropping Organic Molecular Crystals Based on Adaptive Hydrogen Bonding Network Reconstructions

Abstract

Organic molecular crystals are stereotypically considered brittle, fragile, and prone to disintegration, especially when under anisotropic shear forces. However, robust intermolecular interactions and subtle molecular packing motifs may enable a crystal lattice with extraordinary mechanical properties. Here, we present an organic molecular crystal composed of a chiral dithiolane derivative (R-TAE) that can be cropped and cut into arbitrary shapes by external shear forces. Macroscopic R-TAE crystals prepared through a three-solvent diffusion method can be mechanically torn apart by tweezers or precisely cut into desirable shapes, such as semicircles, triangles, triangular waves, pentagons, and stars, by using ordinary scissors, while retaining high crystallinity and structural integrity. Compared with the racemic crystals (RS-TAE), an R-TAE crystal possesses a more flexible and adaptive lattice, enabling the crystal to bend and curl under mechanical stress reversibly. The unconventional yet simple crystal shape programming peculiarity emanates from a specific molecular design and organization that inherently incorporate chiral symmetry-breaking effects in the R-TAE crystal lattice. Moreover, it is revealed that the high asymmetry facilitates effective energy dissipation during the shear force-driven reconstruction of the adaptable hydrogen-bonding network and crystal lattice slippage when the crystal is subjected to shear forces. Instead of cracking or shattering, R-TAE crystals retain their overall morphology intact and exhibit a significant elastic modulus enhancement after ultraviolet-induced disulfide bond reorganization, suggesting robust resistance to photoinduced internal stress. Our research highlights the strategic integration of top-down and bottom-up approaches, resulting in dynamic crystals with desirable anisotropic properties and enabling their precise and straightforward processability.