Elastic Molecular Crystals: From Serendipity to Design to Applications
Soumyajit Ghosh, Manish Kumar Mishra
Abstract
The mechanical adaptiveness of long-range ordered molecular crystals has long been ignored due to their brittle nature, unlike polymers and flexible biomaterials. However, the recent emergence of elastic bendable crystals with exceptional flexibility has changed the perception of molecular crystals. The research on the mechanical properties of molecular elastic crystals has sparked a tremendous interest in the design of mechanically adaptable soft crystalline materials. The current focus of crystal engineering has moved from structure design to property design: i.e., the design of molecular solids with the desired properties. This review provides an overview on the development of elastic molecular crystals starting from their serendipitous discovery to design principles and suitable applications. A molecular-level understanding of mechanical flexibility through a crystal engineering approach can assist us in designing novel elastic bendable crystals combined with other unique properties. The importance of elastic bendable crystals has evoked sufficient recent interest in flexible optoelectronics, semiconductor devices, waveguides, artificial muscles, actuators, electronics, and mechanopharmaceutical applications. The adoption of advanced techniques such as nanoindentation, AFM, micro-Raman spectroscopy, microfocus SCXRD, etc. to analyze the structure–properties correlation both quantitatively and accurately of elastic crystals has paved the way for significant progress. This emerging research area has the ultimate prospect of playing a decisive role in the future growth of crystal engineering.