Alkylamide (-CONHC n H 2n+1 )-substituted benzene and its pyrene derivatives have shown a discotic hexagonal columnar liquid-crystalline phase through a one-dimensional (1D) intermolecular N-H···O hydrogen-bonding interaction, the direction of which is inverted through the application of an alternate current voltage. The polar hydrogen-bonding chains and dipole inversion reveal a ferroelectric polarization-electric field (P-E) hysteresis curve. Non-planar helicene derivatives bearing two CONHC 14 H 29 chains also indicate a ferroelectric response. The racemic helicene derivative shows a bilayer lamellar liquid-crystal phase within a temperature range of 330-420 K, whereas there is no liquid crystallinity for the optically active derivative because of the different molecular assembly structure. The racemic phase is constructed through a two-dimensional (2D) N-H···O hydrogen-bonding network, which shows ferroelectric P-E hysteresis curves at above 340 K. The collective dipole inversion in the 2D layer contributes to the ferroelectricity in the lamellar phase. The remanent polarization (P r ) of 11.1 μC cm -2 is about 6 times higher than those of the planar benzene- and pyrene-based 1D ferroelectrics. Both the density of the hydrogen-bonding site and the domain orientation in the 2D system are higher than those of the 1D columnar system.
ASJC Scopus subject areas
- Colloid and Surface Chemistry