Imperfect defects in smectics A

Polymerisation of twist-bend nematic textures for electro-optical applications

“…Double helices have already been observed in SmA and SmA* phases 32,33 and, like FCDs, they appear to keep the layer thickness constant. 22,32 Again, this reveals a deep analogy between the SmA and N TB phases.…”

“…20 FCD defects directly result from the layered structure of the phase because the periodicity of the layers prohibits twist and bend deformations of the director. 21 Therefore, in order to satisfy the hybrid anchoring conditions, the liquid crystal layers bend and wrap around singular lines taking the form of ellipses and confocal hyberbolas, 22 giving rise to elliptic-hyperbolic FCDs (EHFCDs). Since FCD defects occur due to the presence of a periodic structure, whatever its nature, they are observed not only in the case of a density modulation (as in smectic phases) but also in the case of an orientation modulation (as in cholesteric phases).…”

“…In smectics, the structure of double helices has been explained in terms of screw dislocations of giant Burgers vector. 22 In this model, the double helix represents disclinations of the director and the smectic layers are equally spaced on an helicoid (Fig. 3).…”

Geometry of focal conics in sessile cholesteric droplets

“…Note that in the limit that the blue sphere center moves off to infinity along real branch, it becomes a plane tangent to the cyclide, and the cone becomes an infinite cylinder. This construction is the basis for the construction of large angle grain boundaries ( 16 ) and can also give rise to spatially varying eccentricity in thick enough freestanding films ( 20 – 23 ) or by confining a hybrid-aligned smectic with curved interfaces ( 17 ) by manipulating interface behavior with colloidal particles. Note that a sphere centered on the virtual branch at the diametrically opposed infinity also is a plane tangent to the cyclide.…”

A Review on Physical, Chemical and Optical Properties of Liquid Crystal

“…A precise distinction is made when it comes to azoxy compounds as to whether a pure isomer [only -N(O)=N-] or a combination of both isomers [-N(O)=N-as well as -N=N(O)-] is synthesised and described (Yuriy, 2023). Different systems will mention these two scenarios.…”