Critical behavior at the isotropic to nematic phase transition in a bent-core liquid crystal
2,J. T. Gleeson
Phys. Dept. Kent State U.
Hungarian Research Institute for Solid State Physics and Optics
2Liquid Crystal Institute, Kent State U.
Magnetic birefringence and dynamic light scattering measurements of orientational order parameter fluctuations at the isotropic-nematic phase transition of a bent-core liquid crystal reveal a pretransitional temperature dependence consistent with the standard Landau-deGennes mean field theory. However, the transition in the bent-core compound is more weakly first-order (TNI-T* ~ 0.4C), the leading Landau coefficient is ~ 10 times lower, and the viscosity associated with nematic order fluctuations is ~ 50 times higher, than typically observed in calamitic (rod-shaped) liquid crystals. These anomalies can be explained by an unconventional optically isotropic phase composed of complexes of bent-core molecules, such as recently conjectured for the structure of a “tetrahedratic" liquid crystalline phase.