Hexagonal symmetry for smectic blue phases

Abstract

Smectic blue phases are liquid crystalline phases which exhibit both three-dimensional-orientational order and smectic positional order. X-ray scattering experiments reveal that at least one of these phases is not cubic, as classical blue phases, but offers a hexagonal symmetry. A comparison of the experimental patterns with the scattering patterns given by smectic double twist tubes sketched by Kamien is proposed.

Helical nanofilaments of bent-core liquid crystals with a second twist

“…The double twist of the nanofilaments is also different from the double twist observed in various types of blue phases of either cholesteric 27 or smectic 28 nature. The blue phases are made of chiral molecules that pack into doubly twisted cylinders with a single periodicity and only one sense of chirality determined by the molecular chirality.…”

Resonant X-Ray Diffraction Study of an Unusually Large Phase Coexistence in Smectic Liquid-Crystal Films

“…The observed stable microscopic coexistence suggests an unusually low interface energy (surface tension) between the SmC * d6 and the SmC * d4 structure. Similar situations, where different orders coexist on a microscopic length scale, are found in microemulsions in surfactant systems [19], as well as in one of the recently identified smectic blue phases (BP) [20,21]. In all those situations, the observed structures result from a delicate balance between the ultralow interface tension (elasticity), mixing entropy, and the interactions involved.…”

Smectic Phases with Cubic Symmetry: The Splay Analog of the Blue Phase

“…In general, since smectic ordering is incompatible with cubic symmetry, it is expected that any blue phase structure must include smectic defects as well as orientational defects. Though a model for double-twist cylinders with smectic order has been proposed [8], the simplest variant of that model is incompatible with experimental details [5]. In this letter, we propose a new scheme for constructing a smectic blue phase that fills space with continuous concentric layers with cubic symmetry.…”

“…These three distinct smectic blue phases have been observed near the isotropic transition of these compounds: BP sm 1 has cubic symmetry, while BP sm 2 and BP sm 3 have hexagonal symmetry. The precise physical properties of these materials have been the study of intense investigation in recent years [4,5,6]. However, there is no obvious way to incorporate smectic ordering into the traditional double-twist tube blue phase ordering put forward by Sethna et al [7] for nematic blue phases.…”