Research progress of mechanically flexible molecular crystals: From bending mechanisms to applications

The emerging of flexible molecular crystals is considered as one of the most exciting developments in the organic solid chemistry research as it brings the light for the application in wide range of areas. Understanding the bending mechanism is helpful to design the new flexible molecular crystals with desired mechanical properties. However, the relationship between crystal structure and mechanical properties has not been clearly explored, some explanations for bending can only be given vaguely, and more research are still needed to pave the way for the development of bending principles. Currently, this bending ability is more thought to be related to weak dispersive interactions, for which researchers are working to understand these structure-property mysteries using a variety of qualitative and quantitative means. This perspective summarizes three elastic standards and possible plastic bending mechanisms, comprehensively evaluates the main characterization methods, and points out their usage scenarios and limitations. It emphasizes the key role of the weak interactions in the design of mechanically flexible crystals and provide a short discussion to utilize water molecule to induce the mechanical flexibility. Combined with the current state of flexible molecular crystals, four potential development directions are summarized. It also provides some hints on the evolution towards intelligence and integration to fully exploit the unique value of this material.

Automated summary

The emergence of flexible molecular crystals opens up possibilities for wide-ranging applications, but the relationship between crystal structure and mechanical properties remains to be explored. Weak dispersive interactions play a crucial role in designing mechanically flexible crystals. This perspective summarizes elastic standards, plastic bending mechanisms, characterization methods, and potential development directions.