Dielectric and XRD investigation of ferroelectric liquid crystal composed of banana-shaped achiral molecules

An achiral banana-shaped called F-490 liquid crystal has been examined by means of polarizing microscopy, differential scanning calorimetry (DSC) as well as X-ray diffraction (XRD) and dielectric spectroscopy methods. The phase diagram of the compound is proposed. The F-490 forms crystal-like phases the B4 and the B3 on heating and the banana-like antiferroelectric phase B2 as well the B3 and the B4 phases on cooling. Moreover, the formation of solid phase depends upon thermal history. Dielectric studies have been done with HP set-up in a wide frequency range of 0.01–1.5 MHz using LINKAM 5 μm cells. Dielectric dispersion as well as absorption were calculated from the data. On the base these data the complex rotational dynamics of banana-shaped molecule have been described. The layer thickness and the unit cell parameters of B-phases were determined on the base of XRD results.