Investigation of the electrothermo-optical effect of a smectic LCP-nematic LC-chiral dopant ternary composite system based onSA ? N* phase transition

Abstract

A sharp change in transmittance from a transparent state to a light scattering one within a tiny temperature range is induced accompanied with the heat-induced phase transition from a smectic-A (S A ) phase to a chiral nematic (N*) one in a sidechain smectic-A liquid crystalline polymer ( S A LCP) -low-molecular-weight nematic liquid crystal (NLC) -chiral dopant ternary composite system with a homeotropic boundary condition. By adjusting the polymer ratio, an induced N* phase exhibiting strong light scattering over a wide temperature region has been obtained. The resulting scattering texture retained in the S A phase due to fast cooling from the N* phase can be rather stable and can be easily erased by cooling slowly from the N* phase to the S A phase after the scattering texture being heated into the N* phase again or by application of an alternating current electric field on the scattering texture directly. Based on these characteristics, it is very possible that this composite system will be used as a novel thermal addressed liquid crystal display material with respect to a fast response, a high contrast, and a durable memory effect.

Easily Processable Temperature-Responsive Infrared-Reflective Polymer Coatings

“…23−29 In this way, temperature-responsive reflective systems have been developed for various purposes. 10,25,30−34 Among them, a film made of a CLC elastomer shows reversible reflection band shifting by thermal deformation. 35 However, in the fabrication methods to prepare these systems, the LC is brought into a narrow gap between two glass plates with alignment layers on the inside (an alignment cell), which limits their applications.…”

Effect of cholesteric liquid crystalline elastomer with binaphthalene crosslinkings on thermal and optical properties of a liquid crystal that show smectic A‐cholesteric phase transition

“…Around SmA‐Ch phase transition, the internal cause of the special structure was the competition between the tendency of the molecules to form layers in SmA phase and the helical twist of Ch phase. As the temperature gets closer to SmA‐Ch phase transition, the size of the group of molecules with smectic‐like short‐range order gets much larger, which makes it increasingly difficult for LC molecules to twist, causing the pitch length drastically longer . As a result, the pitch length decreases from infinity to an extent when heating near the SmA‐Ch phase transition.…”

Calculations of helical twisting powers from intermolecular torques

“…In this way, chiral polymer films can be made, which prove useful in improving the viewing angle of displays or can be used as thermally controllable reflective polarizers. [1][2][3] The desire to limit other effects of the chiral molecule ͑such as detrimental effects on elastic constants, dielectric anisotropy, rotational viscosity or induced demixing in a display mixture͒ and the limited solubility of many dopants means that there is considerable interest in designing molecules with high HTP values ͑Ͼ100 m Ϫ1 ͒. 4 In this case, a small quantity of chiral dopant can impart a helical twist without spoiling the other carefully optimized material properties of the host system.…”