posted on 2024-02-10, 14:08authored byAzumi Akiyama, Michinari Kohri, Keiki Kishikawa
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.