Nematic Structures under Conical Anchoring at Various Director Tilt Angles Specified by Polymethacrylate Compositions

Abstract

Dependence of the director tilt angle of nematic liquid crystal (LC) under conical anchoring from the two-component polymer mixture composition has been studied. We varied the ratio of poly(isobutyl methacrylate) (PiBMA), which specifies a conical anchoring for the nematic liquid crystal LN-396, and poly(methylmethacrylate) (PMMA) assigning a tangential alignment for the same nematic. An oblique incidence light technique to determine a tilt angle has been used. It has been shown that the tilt angle increases from 0∘ to 47.7∘ when PiBMA:PMMA ratio changes in the range 30:70 to 100:0. The specific optical textures viewed under the polarizing microscope and proper orientational structures have been considered for various compositions of the polymer films. An electric field action on the formed orientational structures has been investigated. The obtained results are promising for the application in various electro-optical LC devices with a conical anchoring in which the director tilt angle is a crucial parameter: a controlled diffraction gratings, an electrically operated achromatic rotators of linear light polarization, etc.

Electrically Induced Structural Transformations of a Chiral Nematic under Tangential-Conical Boundary Conditions

“…Therefore, the domain border has the topological surface linear defect located at the substrate with conical anchoring. Near this linear defect, the additional twist deformation of the director arises in such a manner that the director at the substrate with conical anchoring in the domain border center is parallel to the linear defect [19,21].…”

“…Moreover, a change in the θ C angle by any method should not result in the critical degradation of a director capacity to gliding. Earlier, we demonstrated the possibility to specify the different director tilt angles on the substrate with conical anchoring using a mixture of polymethacrylates [19]. In the present work, the electrically induced structural transformations within CLC cells with tangential-conical boundary conditions at the various director tilt angles on the substrate under conical anchoring are considered.…”

“…For instance, the polystyrene and polyisoprene assign the conical anchoring for nematic 5CB with the tilt angle θ C = 18 • and θ C = 16 • , respectively [14]. The perfluoropolymer sets for LC CCN-47 the conical anchoring with the θ C angle depending on temperature [18]; the poly(isobutyl methacrylate) (PiBMA) assigns the conical anchoring for the nematic LN-396 with θ C = 47.7 • [19].…”

Photoinduced Transformation of the Orientational Structure of a Chiral Nematic under Planar-Conical Anchoring

“…Интересным является тот факт, что в образце на основе ПтБМА линейные дефекты и ондуляции не возникают, и, исходя из этого, уже можно предположить, что в этой структуре полярный угол наклона директора небольшой. Для проверки данного утверждения нами был изготовлен образец с ориентирующими пленками ПВС и ПтБМА, заполненный нематиком ЛН-396 без хиральных добавок, для которого методом наклонного падения света [15] измерен угол наклона директора на полимере ПтБМА. Полученное значение угла получилось равным 0°.…”

Liquid Crystal Materials under Conical Boundary Conditions

“…Исследования ЖК-систем с коническими граничными условиями показали, что они являются интересными как с фундаментальной, так и прикладной точки зрения. В работе [13] было реализовано управление углом наклона директора в диапазоне от 0° до 50°, что в дальнейшем позволит исследовать влияние величины угла θ на формирующиеся структуры, и может быть использовано для улучшения оптических и электрооптических характеристик ЖК-материалов с коническим сцеплением.…”