Critical Behavior at the Isotropic-To-Nematic Phase Transition in a Bent-Core Liquid Crystal

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, as follows: the transition in the bent-core compound is more weakly first order (T(NI)-T(*)approximate to 0.4 degrees C), the leading Landau coefficient is similar to 30 times lower, the viscosity associated with nematic order fluctuations is similar to 10 times higher, and the density change is similar to 10 times lower, than typically observed in calamitic (rod-shaped) liquid crystals. One consistent explanation for these anomalies is an optically isotropic phase composed of microscopic complexes or "clusters" of bent-core molecules.