2D Elastic Organic Crystals with Thermomechanical/Acid Responses and Dual‐Mode Optical Waveguides

Abstract Achieving the combination of multiple external stimuli responses and mechanical flexibility has become the current emerging research in the field of crystalline materials. Meanwhile, the modulation of its properties remains challenging. In this work, a 1‐[(E)‐[(6‐methyl‐1,3‐benzothiazol‐2‐yl) imino] methyl] naphthalen‐2‐ol (BNO) crystalline material is reported. The modulation of the mechanical elasticity and thermomechanical responses is achieved by means of polymorphism (form‐I and form‐II). Further, the structural basis of the 2D mechanical properties of form‐I is investigated. Meanwhile, two types of thermomechanical responses appearing in form‐I are explored in detail from the perspective of crystal structure and thermodynamics, and the second thermomechanical response during cooling is successfully predicted. Then, the acid response of the materials is endowed by molecular design, the fluorescence switch is realized through acid and thermal treatments. Finally, the active/passive dual‐mode optical waveguides of the materials are explored.