Rapid, solvent-minimized and sustainable access to various types of ferroelectric-fluid molecules by harnessing mechano-chemical technology

Abstract

Recently, ferroelectric fluid, such as ferroelectric nematic liquid crystals (N_FLCs) and ferroelectric smectic A LCs (SmA_FLCs), has been of great fundamental and practical interest owing to its excellent polarization properties (e.g., dielectric permittivity, polarization, and nonlinear optical coefficient). To deeply understand the physical underpinning of such emergent ferroelectric phases and develop state-of-the-art device applications, effective preparation of various N_F molecules is essential. Herein, to expand the N_FLC molecular library, we implemented a mechanochemical (MC) technique for the production of LCs, demonstrating its high synthetic compatibility with N_F/SmA_FLCs. Chemical building blocks with high polarity can be bonded one by one through various ball-milling MC reactions, resulting in rapid access to N_FLC molecules, a series of DIO, RM734, UUZU, and BIOTN, with high yield within 2.7–7 h for 4–8 steps. For a new DIO variant, in which a terminal alkyl chain was completely removed, for the first time, we discovered the direct phase transition from the isotropic liquid to the SmA_F phase. Furthermore, the highly bistable polarization memory (∼5.2 μC cm⁻²) in the SmA_F phases was evaluated using the positive–up–negative–down (PUND) method.