Scientific News
A novel nematic liquid crystal phase with ferroelectric response
Ferroelectric switching was observed for a nematic liquid crystal consisting of bent-core polar molecules. X-ray diffraction shows that this originates from the cooperative alignment of nanometric size polar and biaxial cybotactic groups present in the nematic phase. This discovery discloses the way toward ferroelectric fluids that can be aligned using a simple electric field.
August 2009 - The elusive ferroelectric nematic liquid crystal phase promises spontaneous long range polar order coupled with fluidity and the ability to self-heal. The search for this phase is fuelled by fundamental and technological perspectives in the field of electro-optical devices with fast response to an electric field. Its properties are expected to be very different from those of conventional ferroelectric liquid crystals, namely more solid-like smectic phases, which are typically formed by chiral mesogens. The existence of such ferroelectric nematic liquid crystals is not forbidden from a theoretical point of view [1]. However, despite years of intensive experimental quest, no successful demonstration of ferroelectric nematic liquid crystals has yet been given in low molar mass thermotropic systems.
Here we present evidence of a ferroelectric response in the nematic phase of a bent-core mesogen, the 3,5-bis-{4-[4-(n-nonyloxy)benzoyloxy] phenyl}-1,2,4-oxadiazoles (9BPO in Figure 1) [2]. By combining repolarisation current measurements, electro-optical characterisation, synchrotron X-ray diffraction studies, and computer simulations, we demonstrate the ferroelectric switching response and show that the macroscopic bulk polarisation involves long-range orientational ordering of polar cybotactic clusters [3].