The Role of the 1,2,3-Triazolyl Heterocycle in the Helical Columnar Assembly and Electric Field Response

Helical Columnar Liquid Crystal Exhibiting Both Polarization Retention and Ferroelectric Switching at Room Temperature

Ferroelectric columnar liquid crystals (FCLCs) with switchable bistable axial polarizations are promising candidates for high-density ferroelectric random-access memory (FeRAM). However, FCLCs simultaneously exhibiting uniform polarization arrangement and ferroelectric switching at room temperature (RT) remain elusive. Herein, we report an RT-operable FCLC based on C3-symmetric star-shaped mesogen with polar linkers. Two CLCs, 1 and 2, were synthesized incorporating 1,2,3-triazole and amide linkers, respectively. 1 undergoes a ferroelectric-to-paraelectric transition accompanied by a structural change from helical to a nonhelical columnar phase. Notably, the ferroelectric switching is operable down to RT, with complete retention of its axial macrodipole after removal of the electric field. In contrast, 2 forms only a nonhelical columnar LC phase, displaying paraelectric behavior. The contrasting self-assembly and dielectric properties are attributed to the differences in the polar unit size. This study demonstrates that the mesogen extension with a bulky 1,2,3-triazole linker enables the realization of an FCLC operable at RT, offering significant potential for high-density FeRAM applications.

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.