Line shapes of field-induced blue-phase-III selective reflections

Abstract

We have measured the electric-field dependence of the reflectivity of the blue phase III (BP III) of cholesteric liquid crystals when the dielectric anisotropy e a < 0. We propose a model which assumes that the boundary aligns the sample to a depth L and in which L is increased by the applied field. The free energy is proportional to E" y where n depends on the structure of BP III. The data are fitted well by a Lorentzian line shape, and the peak intensity and linewidth agree well with the theory for n =2.1. This value is consistent with the double-twist model of BP III, but not with cubic and quasicrystal models, since the energies of these latter structures depend on higher powers of E.

Spatial dispersion in chiral liquid crystals. Effects of higher orders

“…The blue phases I and I1 show qualitatively different line shapes. This result contradicts conclusions based on measurements of the line shape-electric field dependence in the BPIII [35]. The relation of the lattice period of the blue phases to the wavelength of light is of the order of unity.…”

DNA liquid crystalline blue phases. Electron microscopy evidence and biological implications

“…We have observed here at least two of them. The first one corresponds to a loose random network of double twist cylinders, which is consistent with the spaghetti model of BP I11 [24,25]. This phase, that has hitherto been described as macroscopically amorphous, while locally highly ordered, still remains somewhat enigmatic.…”

“…This phase, that has hitherto been described as macroscopically amorphous, while locally highly ordered, still remains somewhat enigmatic. Three main models have been proposed: (i) the spaghetti model as a spaghetti-like tangle of double twist cylinders [24,25], (ii) the cubic domain model in which double twist tubes form local small cubic domains that are randomly oriented relative to one another [20,26] and (iii) the quasi-crystal model that abides by an icosahedral symmetry [22, 271. DNA solution could provide an accurate tool to further investigations of this enigmatic BP I11 structure. Indeed, our observations not only support the spaghetti model, but also allow one to specify it.…”

Electro‐Optical Switching in a Blue Phase III Exhibited by a Chiral Liquid Crystal Oligomer

“…[6] It can be expected that BPIII consists of double twist cylinders with arbitrary orientation. [2,7,8] Usually, blue phases are found in a very narrow temperature range (ca. 1 K) between the isotropic liquid and the chiral nematic (N*) phase of sufficiently short pitch, except in a few cases where a SmA to BP transition has been observed.…”