CUBIC AND BLUE PHASES IN A FLUORINE-CONTAINING DICHIRAL COMPOUND

Abstract

The structure and dynamics in an optically isotropic liquid crystalline phase exhibited in a dichiral compound with fluorines have been investigated using X-ray, 19F-NMR and dielectric measurements. Results in the dielectric measurement and 19F-NMR measurements clearly show that molecular motion in this phase is just like in the isotropic phase as observed by texture. However, several X-ray diffraction peaks observed in a small angle range indicate akind of cubic phase (Cub). Based on the X-ray diffraction patterns together with the existence of circular dichroism, the phase is assigned to a chiral cubic structure belonging to crystallographic spacegroupI432. Moreover, the exotic phase with blue colored and foggy texture was found in the lower temperature range of isotropic liquid. X-ray diffraction in this phase clearly shows a diffraction ring corresponding to a layer structure, indicating that this blue-colored phase is assignable to a smectic blue phase (BPsm). It was also found that the layer correlation length is remarkably long compared with the previously reported BPsm phases. We want to emphasize that the present material is quite unique in the sense that both cubic phases, BPsm and Cub, appear. The influence of cell thickness and incubation time on the emergence of the smectic C* phase is also discussed based on dielectric measurements and AC calorimetry.