Room-Temperature Reversible Control of Fluorescently Distinct Polymorphs Using Pressure and E-Field: Writing and Erasing Information without Thermal Treatment

This paper presents the reversible transformation between two polymorphs of a hexacatenar liquid crystal (1) with distinct fluorescence colors at room temperature (RT). This method utilizes mechanical pressure (mechanochromism) and an electric field (E-field-chromism). The molecule (1), designed with a pyrene core and 1,2,3-triazole linkers, exhibits a blue-emissive crystalline (CRY) polymorph (1-B) and a green-emissive liquid crystalline (LC) polymorph (1-G) at RT, depending on the cooling rate from the liquid phase. The metastable 1-G is stabilized by hydrogen bonding (H-bonding) between 1,2,3-triazole linkers, forming a helical columnar structure. Mechanical pressure converts thermodynamically stable 1-B to 1-G, while the application of an alternating current (AC) E-field to 1-G transforms it back to 1-B. Notably, this study reports the first instance of an E-field-induced polymorphic transformation. Using mechanical pressure and E-field application at RT, patterns were successfully recorded and erased on substrates, demonstrating potential applications in data storage, anticounterfeiting, and sensor technologies.