Room-Temperature Ferroelectric Columnar Liquid Crystals Driven by a Low Electric Field

The realization of ferroelectric columnar liquid crystals (FCLCs) capable of axial polarization switching along the column axis at room temperature (RT) is an important breakthrough in the practical application of FCLCs. However, molecules exhibiting FCLC phases generally have low fluidity at RT, which inhibits the response of polar functional groups to an applied external electric field, making changing the direction of the column polarity difficult. Here, we report RT-FCLCs, N,N′-bis(3,4-dialkoxyphenyl)ureas, driven by a low electric field. The introduction of bulky branched alkyl chains lowered the temperature range of the columnar liquid crystal phases, resulting in a fluid-assembled state with moderate hydrogen bonding that allowed polarization switching at RT. Comparison of these synthesized ureas revealed that reductions in the bulk and length of the side chains produced longer retention times of the polarization. Our thermodynamic analyses clarified that these ureas have high enough depolarization activation energy to maintain polarization, despite a low coercive field of a few V μm^–1. Furthermore, the retention time of the columnar liquid crystal phase dramatically increased as the temperature neared RT, indicating an increase in the slowness of molecular motion, reminiscent of the vitrification process. We established a methodology to achieve FCLCs with the desired performance by selecting the alkyl chain to be introduced.