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

Abstract

2009) Effects of the preparing condition of a polymer-stabilised liquid crystal with a smectic-A-chiral nematic phase transition on its properties, Liquid Crystals, 36:2, 165-172, 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.

A Review of Developments in Polymer Stabilized Liquid Crystals

“…Like CLCs, the planar molecular alignment in the SmA phase is also stabilized with polymer networks. G. H. Pan et al have fabricated PSLC films switching between a transparent state at lower-temperature environment and a light-scattering state at a higher-temperature environment based on the LC host with an SmA-CLC phase transition [56][57][58]. Firstly, the mixture of photo-curable LC monomer, non-curable LC monomer and chiral dopant is filled into the LC cell (Figure 5a, step 1).…”

“…Photographs of PSSLC film are shown when the environmental temperature is below and above the SmA phase to CLC phase transition point; the film is transparent and scattered, respectively (Figure 5b) [57]. Consequently, the PSSLC films can be applied in light shutters, E-papers, alarm devices for overheating protection, and thermoelectrical sensors [56][57][58]. Recently, in the SmA phase, the direct distribution of focal conic domains (TFCDs) is generated with the polymer stabilization strategy.…”

Preparation and thermo-optical characteristics of a smart polymer-stabilized liquid crystal thin film based on smectic A–chiral nematic phase transition

“…The PSLC films [30] were prepared by ultraviolet (UV) radiation-induced crosslinking polymer network in the parallel-oriented chiral nematic (N*) phase of the photpolymerisable monomer/LC/photoinitiator mixture, showing the electrical-addressing and thermal-erasing characteristic between the smectic-A (SmA) and N* phase. On the other hand, with polymerizing in a homeotropically oriented SmA phase, the PSLC exhibited a sharp change occurring from a transparent to a light-scattering state when heated from SmA to the N* phase [30,42], and could be electricity-controllable as a shutter in N* phase [43][44][45].…”

“…Consequently, the temperature scope of the transition between the SmA and N* phase, belonging to the continuous phase transition [49,50], is extremely confined, and the PSLC films based on SmA-N* phase transition exhibit excellent temperature sensitivity in different optical performance switching. The thermo-optic and electro-optic characteristics of the PSLC films based on the SmA-N* phase transition have been explored by Yang et al [30,[42][43][44][45].…”