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 $(T_{NI}-T^{*}\approx 0.4°\mathrm{C})$, the leading Landau coefficient is $\sim 30$ times lower, the viscosity associated with nematic order fluctuations is $\sim 10$ times higher, and the density change is $\sim 10$ 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.

• Received 8 November 2005

DOI:https://doi.org/10.1103/PhysRevE.73.030703