Short-Range Smectic Order in Bent-Core Nematic Liquid Crystals

Small angle X-ray diffraction from the uniaxial nematic phase of certain bent-core liquid crystals is shown to be consistent with the presence of molecular clusters possessing short-range tilted smectic (smectic-C) order. Persistence of these clusters throughout the nematic phase, and even into the isotropic state, likely accounts for the unusual macroscopic behavior previously reported in bent-core nematics, including an anomalously large flexoelectric effect ( 1000 times that of conventional calamitic nematics), very large orientational and flow viscosities ( 10–100 and 100–1000 times, respectively, typical values for calamitics), and an extraordinary flow birefringence observed in the isotropic state.