On the biaxiality of smectic C and ferroelectric liquid crystals

Jones, John C.

doi:10.1080/02678292.2015.1028492

Cited by 9 publications

(12 citation statements)

References 42 publications

(53 reference statements)

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“…The molecule has a ratio of polarisability anisotropy to the average as ( ) 0.47 and a high biaxiality of the polarisability tensor with ( , 1 being along the shortest molecular axis). Assuming that the phase biaxiality order parameter C for the SmCP phase is equivalent to that of a typical smectic C [55], the optical biaxiality is of the order of half the uniaxial nematic birefringence (∂ ≈ 0.4).…”

Section: The Bent-core Liquid Crystalmentioning

confidence: 99%

Dark conglomerate phases of bent-core liquid crystals

Nagaraj

2016

Liquid Crystals

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Spontaneous or induced chiral symmetry breaking in achiral systems is unusual and understanding the origin of such a phenomenon has been an important area of research for several years. The optically isotropic mesophases exhibited by unconventional liquid crystals are one of the most interesting systems to investigate spontaneous chiral symmetry breaking in liquid crystal mesophases formed by achiral moieties. The dark conglomerate (DC) phases are one such optically isotropic family of phases. In this paper, a detailed account of the tendency of bent-core mesogens to form a variety of polar smectic phases, the formation of DC phases due to layers deformations and the general optical, electrical, physical properties of the DC phases are given. An example of a dark conglomerate phase which exhibit distinct electro-optic properties is described with the nature of dynamics of the response and physical reasons responsible for such behaviour. The challenges and prospects of the dark conglomerate phases are discussed for their potential applications in novel devices.

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Section: The Bent-core Liquid Crystalmentioning

confidence: 99%

Dark conglomerate phases of bent-core liquid crystals

Nagaraj

2016

Liquid Crystals

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“…Полученный результат вполне согласуется с резуль-татами рентгеновских исследований смектических слоёв [10,12].…”

Section: электрическое поле включеноunclassified

Determination of optimal chevron configurations in surface-stabilized smectic C*

Migranov¹,

Kudreyko²,

Migranova³

2016

LoM

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Configuration properties of layer orientation in smectic C* type ferroelectric liquid crystals are theoretically described for constant temperature. The model proposed admits both symmetric and asymmetric configurations of smectic layers [chevron structures] in surface-stabilized liquid crystal cells, which [chevron structures] perturb ordering of smectic C* molecules in the so-called bookshelf geometry. The considered model reasonably disregards mass transfer between the smectic molecular layers. Since the length of smectic layers is permanent for any coordinate of the chevron tip, because of the fixed polar angle θ, the locus of the chevron tip can be represented by ellipse. By using the continuum approach, the functional of the free energy density with the quadratic term of the electric field density is found. To determine energetically favorable structures of molecular layers, the Euler-Lagrange equation was solved, which is the dependence of the director's azimuthal angle φ-from the direction normal to the cell substrates. It is shown that only symmetric chevron structures exhibit minimum of free energy in the absence as well as in the presence of the electric field. This effect is caused by splay deformation of smectic layers. The stability analysis of the Euler-Lagrange equation for typical values of electric field and smectic C* parameters shows that the theoretical results are in agreement with the experimental data. The approach proposed for studying of the chevron configurations can explain the abundance of textures in smectic C* liquid crystal cells. Проведено теоретическое описание конфигурационных свойств слоёв сегнетоэлектрических жидких кристаллов типа смектик C* при постоянной температуре. Предлагаемая в этом письме модель допускает симметричные и не-симметричные формы смектических слоёв [шевронные структуры] в поверхностно-стабилизированных жидкокри-сталлических ячейках, которые нарушают геометрию упаковки молекул -так называемой «книжной полки». Рас-сматриваемая модель обоснованно не учитывает массоперенос вещества между молекулярными слоями смектика C*. Поскольку длина смектических слоёв при изменении положении излома остаётся постоянной ввиду фиксированного значения полярного угла θ, то в рассматриваемой модели геометрическое место точек излома смектических слоёв представляет собой эллипс. С помощью континуального подхода, получен функционал плотности свободной энергии системы с учётом квадратичного слагаемого, связанного с энергией электрического поля. Нахождение энергетически выгодных структур молекулярных слоёв производится с помощью решения уравнения Эйлера-Лагранжа -зависи-мости азимутального угла директора φ от направления, перпендикулярного подложкам ячейки. Показано, что только симметричная структура шеврона обеспечивает минимум свободной энергии слоя смектика C* [как при включённом так и выключенном электрическом поле]. Причиной такого поведения свободной энергии является сплей-деформа-ция смектических слоёв. Анализ стабильности решения уравнения Лагранжа для диапазона допустимых зн...

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“…Ferroelectric liquid crystals (FLCs) were a highly popular research subject for the display industry in the 1980s and 1990s, due to their sub-millisecond switching times and inherent bistability [1]. Technologies such as the Surface Stabilised FLC (SSFLC) [2] seemed suited as an alternative to nematic-based LCDs since high complexity passive displays could be made without thin-filmtransistors at each pixel.…”

Section: Introductionmentioning

confidence: 99%

“…Unwanted helical twist from one surface to the other is ensured by decreasing the chirality of the SmC*, thereby leading to a uniform surface stabilised homeotropic state. Uniform alignment occurs for the condition satisfies P(T) > 4d [1] where P(T) is the helical pitch of the FLC, and d the cell gap, calculated from the Gooch-Tarry equation for a TN device [9]:…”

Section: Introductionmentioning

confidence: 99%