Jinbao Guo

Polymer stabilized liquid crystal films reflecting both right-and left-circularly polarized light

A single-layer polymer stabilized liquid crystal (PSLC) film reflecting both right- and left-circularly polarized light has been developed by a wash-out/refill method. The PSLC film was achieved by prefabricating the polymer network with a left-handed helical structure and then refilling a cholesteric liquid crystal with a right-handed helical structure into the network. The reflection intensity of the PSLC film is close to 100% when the pitch lengths of the two opposite helical structures are the same. It was demonstrated that the memory effect of the polymer network is an important mechanism for the resulting film properties.

Reflectance properties of polymer‐stabilised cholesteric liquid crystals cells with cholesteryl compounds of different functionality

In this paper, we describe the synthesis of cholesteryl compounds of different functionality. A series of polymer‐stabilised cholesteric liquid crystal (PSCLC) cells are prepared by photo‐polymerisation of a cholesteric liquid crystal (Ch‐LC) mixture containing a non‐reactive liquid crystal, a nematic diacrylate and the above cholesteryl compounds. The effect of cholesteryl compound functionality on the morphology and the reflectance properties of PSCLC cells is evaluated, as are parameters such as the polymerisation temperature. The results indicate that the higher functional cholesteryl compound is more effective for broadening the reflection band of the Ch‐LC composites, which is speculated to be a result of the pitch differences in the local network environment. Scanning electron microscopy is used to examine the morphologies of the polymer network of the PSCLC cells. We have found that the morphologies of the polymer network are determined by the functionality of the cholesteryl compounds as well as polymerisation temperature, which further influence the reflectance properties of the composites.

Effects on thermo‐optical properties of the composition of a polymer‐stabilised liquid crystal with a smectic A–chiral nematic phase transition

A photopolymerisable monomer/liquid crystal (LC)/chiral dopant/photoinitiator mixture with a smectic A (SmA*)–chiral nematic (N*) phase transition was prepared. After the SmA* phase was homeotropically oriented and then irradiated by ultraviolet light, a homeotropically oriented polymer network was formed in the SmA* phase and then a homeotropically oriented polymer network‐stabilised liquid crystal (PSLC) film with a SmA*–N* phase transition was prepared. In the temperature range of the SmA* phase, the LC molecules were homeotropically oriented and the film exhibited a transparent state. However, in the temperature range of the N* phase, the film exhibited a strong light‐scattering state owing to the fact that the LC molecules adopted a focal conic alignment affected by the homeotropically oriented polymer network. The strong light‐scattering state of the N* phase could be changed into a transparent one when an electric field was applied. The focus of this study was on the effects of composition of the PSLC film on its thermo‐optical and electro‐optical properties.

Super wide-band reflective polarisers from polymer stabilised liquid crystal films

A polymer stabilised liquid crystal film with the order and the molecular alignment of a smectic-A phase at a microscopic level, but with the planar molecular alignment of a chiral nematic phase at a macroscopic level, was prepared. This kind of order and alignment of the molecules of the liquid crystal resulted in the film reflecting circularly polarised incident light with the bandwidth of the spectrum over the wavelength range of 300–2500 nm.

Effects of the preparing condition of a polymer-stabilised liquid crystal with a smectic-A−chiral nematic phase transition on its properties

A homeotropically-oriented polymer network stabilised liquid crystal (PSLC) film with a smectic-A (SmA)–chiral nematic (N*) phase transition was prepared. In the temperature range of the SmA phase, the liquid crystal (LC) molecules were homeotropically oriented and the film showed a transparent state. However, in the temperature range of the N* phase, the film showed a strong light scattering state due to the LC molecules adopting a focal conic alignment affected by the homeotropically-oriented polymer network. Moreover, the strong light scattering state of the N* phase could return to the transparent state when an electric field is applied on it. The focus of this study is on the effects of the preparing conditions of the PSLC film, including the curing temperature and the intensity of the ultraviolet (UV) irradiation on its thermo-optical and electro-optical properties.