Effective long-range interlayer interactions and electric-field-induced subphases in ferrielectric liquid crystals

Abstract

Microbeam resonant x-ray scattering experiments recently revealed the sequential emergence of electricfield-induced subphases (stable states) with exceptionally large unit cells consisting of 12 and 15 smectic layers. We explain the emergence of the field-induced subphases by the quasimolecular model based on the Emelyanenko-Osipov long-range interlayer interactions (LRILIs) together with our primitive way of understanding the frustration in clinicity using the q E number defined asand [L] refer to the numbers of smectic layers with directors tilted to the right and to the left, respectively, in the unit cell of a field-induced subphase. We show that the model actually stabilizes the field-induced subphases with characteristic composite unit cells consisting of several blocks, each of which is originally a ferrielectric three-layer unit cell stabilized by the LRILIs, but some of which would be modified to become ferroelectric by an applied electric field. In a similar line of thought, we also try to understand the puzzling electric-field-induced birefringence data in terms of the LRILIs.

Resonant x-ray scattering observation of transitional subphases during the electric-field-induced phase transition in a mixture of Se-containing chiral smectic liquid crystals

“…proposed by Chandani et al [35] under an electric field is the same as the present one, but those authors concluded that the "q E n = 3" model was difficult to be stabilized from the free-energy density point of view. Furthermore, the sequential phase transition, i.e.…”

“…21), where only the two peaks at q/q o = 4/9 and 5/9 are strong. The other two calculations [35,36] discussed the possibility of the {R 3 (R 2 L) 2 } configuration, i.e. the same as the present one.…”

“…As far as the authors know, for the C 9p structure, no experimental RXS data has been documented, whereas three molecular configurations were proposed based on theoretical consideration [10,35,36]. The nine-layer periodic phase without an electric field was discussed by Emelyanenko and Osipov [10], in which the distorted clock version of the {R (RL) 4 } configuration was proposed.…”

Transitional subphases near the electric-field-induced phase transition to the ferroelectric phase in Se-containing chiral smectic liquid crystals observed by resonant x-ray scattering

“…From geometrical conditions, the practical q/q 0 resolution of the measurement was less than 0.005, though it depended on the counting statistics in practice. Finally, the RXS intensity in the present experiment was mainly due to σπ scattering (π incident and σ scattered X-rays) because the incident beam was π polarized with respect to the reflection plane in our experimental arrangement and that the RXS theory predicts that the contribution from ππ scattering is very weak [40].…”

“…Chandani et al [40], the C 6p {R 5 L} structure appeared as one of the possible configurations in the electric-field induced phase transition. The superlattice structures recently proposed [47] might coincide with our transitional subphases (q E = 1/2 and 3/5 for C 4p2 and C 5p , respectively), though the sample, the experimental conditions were different from our experiments.…”