Structure and kinetics of ferroelectric smectic nuclei at the chiral nematic–smectic C∗ phase transition under the influence of electric fields

Abstract

In the ferroelectric liquid crystal 3-octyloxy-6-[2-fluoro-4-(2-fluoro-octyloxy)phenyl]pyridine (FFP), having the transition smectic C∗ (S∗_C)-chiral nematic (N∗), the formation of the induced S∗_C phase under external electric fields was investigated. In the N∗ phase, close to the transition temperature T_{s∗ c∗ N∗}, the induction of a strongly twisted S∗_c phase is possible. In the case of AC voltage, the growth of nuclei of the S∗_c phase can occur through the formation of circular smectic layers. Dependent on the frequency and amplitude of the electric field, the S∗_C helix within the circles can be twisted or untwisted. This leads to different resulting colours of the circles due to the different anisotropies of the average refractive index and their wavelength dispersion. The coexistence of twisted and untwisted smectic circular nuclei with the supertwisted nematic phase looks like a flower garden (‘Darmstädter Blumengarten’).