Preparation and electrooptic study of reverse mode polymer dispersed liquid crystal: Performance augmentation with the doping of nanoparticles and dichroic dye

Abstract

Reported herein, the preparation, morphological, and electrooptic (EO) characterization of reverse mode polymer dispersed liquid crystals (PDLCs) with nematic liquid crystal (LC) and UV curable polymer optical adhesive using polymerization induced phase separation method. The PDLCs are switchable between transparent and opaque states due to the homeotropic and planar alignment of LC in their OFF and ON states of applied voltage, respectively. Further, effect of doping of a fixed concentration of azo dye and silica nanoparticles (NPs) on morphological, EO and response characteristics of same PDLC sample was also analyzed. Experimental results showed that doped reverse mode PDLCs have the higher OFF state optical transmission and boost up in the scattering ON state compared with pristine reverse mode PDLC. The phenomenon is also supported by extinction coefficient and absorption study based on Beer's law. The threshold and operating voltages were found reduced ~1.56 and ~1.73 times for NPs and (NPs + dye) doped reverse mode PDLCs, respectively, along with better contrasts to the pristine reverse mode PDLC. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48745.

Preparation of Highly Durable Reverse-Mode Polymer-Stabilized Liquid Crystal Films with Polymer Walls

“…But the driving voltage increased significantly when the polymer concentration exceeded 5%, the transmittance at the on-state was greater than 10%. Sharma et al , analyzed the effect of doping of a fixed concentration of dye and silica nanoparticles (NPs) on morphological, electro-optical performances, and response characteristics of the same reverse-mode PDLC sample. It was found that with the doping of nanoparticles and dichroic dye, the reverse-mode light shutter showed a better contrast ratio (CR) and a low driving voltage.…”

Printed Polymer‐Stabilized Chiral Nematic Liquid Crystal Privacy Windows

“…[8] Each of these systems can give rise to a light scattering state or a transparent state depending upon the material combination, device architecture, and electric field conditions. Polymer-stabilization has also been combined with CLCs (PSCLCs), as first introduced by Yang from Kent State University in 1992 [9] A notable benefit of using PSCLCs in comparison to say PDLCs is that they can exhibit both a conventional mode (whereby the device switches from a scattering to a transparent state with an alternating current (AC) electric field) and reverse mode (switching from a transparent to scattering state) by simply changing the photopolymerization conditions rather than having to change the LC material (positive dielectric anisotropy LC for conventional mode [10][11] and negative dielectric anisotropy LC for reverse mode [12][13] ) For example, if the PSCLC is photopolymerized while a voltage of sufficient amplitude is applied to the LC film then it can exhibit an opaque/light scattering state in the voltage off state. However, when a voltage is applied to the LC, the helical structure unwinds forming a nematic LC with a homeotropic alignment, [9] which appears transparent.…”

Electrically Induced Optical and Structural Response of Cholesteric and Nematic Droplets with Conical Boundary Conditions

“…В настоящее время многие исследования КПЖК материалов сосредоточены на улучшении электрооптических характеристик КПЖК-пленок (управляющих напряжений, коэффициента пропускания, контрастного отношения). Так, например допирование ЖК дихроичным красителем позволяет увеличить контрастное отношение [9], добавление в ЖК наночастиц или использование модифицированной полимерной матрицы позволяет снизить управляющие напряжения [10,11]. Задание конических граничных условий в каплях нематика позволяет одновременно уменьшить управляющие напряжения, достичь больших коэффициентов пропускания во включенном состоянии и значительного контрастного отношения CR [12,13].…”