Terahertz spectroscopy in smectic phases of a bent-core molecule

The dynamics of a bent-core molecule in two smectic phases is studied using terahertz (THz) spectroscopy, which enables us to observe some rapid molecular motions and segmental motions reflecting intermolecular interactions. The isotropic liquid, liquid crystal and crystal phases of the bent-core liquid crystal P-8-PIMB are clearly distinguished by THz spectra. Unexpectedly, the transmittance in the B3 phase, which has been assigned to either a highly ordered smectic or crystal phase from results of x-ray diffraction analysis, is almost the same as that in the switchable liquid-crystalline B2 phase. This suggests that the molecular dynamics in the B3 phase is liquid-crystal-like on this time scale.