Chiral Nematic Polymer Mixture Containing Crosslinker and Photosensitive Chiral Dopant: New Type of Materials with Tunable Photo‐Optical Properties

A cholesteric mixture based on a menthyl‐containing copolymer, photosensitive chiral dopant, mesogenic diacrylate, and photoinitiating agent has been prepared. The mixture shows a selective light reflection in the visible light spectral region. The action of UV irradiation (313 or 365 nm) on the planar‐oriented films generates the occurrence of two parallel processes: E/Z (i.e., cis–trans) photoisomerization of the chiral dopant and photopolymerization of the diacrylate. The first process leads to the untwisting of the cholesteric helix and shifts the selective light‐reflection maximum to the long‐wavelength spectral region, whereas the second process leads to the development of a polymer network that fixes the helical supramolecular structure. As a result of a simultaneous occurrence of the two above‐mentioned processes, the shift in the selective light‐reflection maximum is thermally irreversible, even though the Z/E isomerization of the chiral dopant itself can be reversed by annealing. On irradiation with visible light (>450 nm), the dopant experiences the E/Z isomerization but photopolymerization is absent because the photoinitiator shows no absorption in this spectral region. In this case, the shift in the selective light‐reflection maximum can be reversed to its initial value by annealing, whereby the original helix pitch is recovered. The kinetic features of helix untwisting at different temperatures and light wavelengths were studied. The experimental data obtained in this work allow one to conclude that the as‐prepared mixture presents a new multifunctional material with “tunable” photo‐optical properties and may be used for recording and storage of optical information.     

低功耗大尺寸胆甾型液晶显示器的发展

与主动发光型显示器相比,反射型显示器具有功耗低,特别是适用于低能耗系统的优势。但在某些情况下,系统的功耗往往大于显示器功耗。     

新型滤色器

介绍了一种新方法制造的彩色滤色器，该滤色器制造方法简单，仅含有一次涂覆和两次曝光。滤色器有好的色纯度和高的显示对比度。     

电场对负性介电常数各向异性的小分子胆甾相液晶的作用

介绍和总结了边界条件影响很大的受限胆甾相和聚合物分散小分子胆甾相液晶（PDCLC）两种情况下，外电场对负性介电常数各向异性的小分子胆甾相液晶的作用。前者的研究通过在不变螺距p情况下改变液晶盒鹌鹑d与外电场电压值E，发现了规律性变化的液晶相的相态结构。而对PDCLC的研究中，通过平行和垂直于电场方向的观察，得到了胆甾相变化与外加电压的具体关系，以及在彩色液晶显示上应用。     

楔型液晶盒对入射激光偏振态的影响

为了研究手性液晶传输距离的变化对入射激光偏振态的影响,通过连续改变入射激光在手型液晶中的传输距离,楔型手性液晶盒可以有效地改变入射激光束的偏振状态,使之从初始的线偏振状态变成了近似的圆偏振光,且同初始的入射偏振方向无关。理论计算和实验结果表明,该方法可用于液晶退偏器的理论分析和设计。     

Controlling the Color of Cholesteric Liquid‐Crystalline Films by Photoirradiation of a Chiroptical Molecular Switch Used as Dopant

Using thin films of a cholesteric mixture of acrylates 2 and 3 doped with the chiroptical molecular switch (M)‐trans‐ 1 , photocontrol of the reflection color between red and green is possible. This doped liquid‐crystal (LC) film can be used for photoinduced writing, color reading, and photoinduced locking (via polymerization) of chiral, optically written information.     

一种新型的聚合物网络胆甾液晶显示器

在胆甾液晶材料中掺入少量的聚丙烯类单体材料制作了一种新型的聚合物网络胆的液晶显示器。相对于传统的ＰＤＬＣ器件，这种新型显示器可以进行反模式显示，零电场时呈透明态，加电场呈散射态．而且还具有非常宽阔的视角特性。文中报道了器件的制作方法以及聚合物网络对器件电光特性的影响，并且对该器件的应用前景作了简要介绍。     

Wearable Optical Sensing of Strain and Humidity: A Patterned Dual-Responsive Semi-Interpenetrating Network of a Cholesteric Main-Chain Polymer and a Poly(ampholyte)

Main-chain cholesteric liquid crystal polymers are a promising candidate for the development of responsive photonic devices due to the combination of selective reflection and soft, elastic properties, but it is difficult to enhance these materials with new kinds of responsiveness due to the inherent lack of mesogenic side groups. Here, a new strategy is showed to obtain a dual-responsive elastic cholesteric polymer material by preparing a semi-interpenetrating network consisting of a cholesteric main-chain polymer and a hygroscopic poly(ampholyte). The material is shown to undergo a redshift of the reflected color upon swelling with water, while the color blueshifts when a strain is applied. Color patterns can be prepared by localized photopolymerization at different temperatures, leading to brightly colored responsive images with high contrast. Due to the elastic nature of the material, it can easily be made into a wearable device, and its application as a multifunctional smart sensor for sweat detection and movement detection is demonstrated. The results show that new responsiveness can be added to main-chain cholesteric polymers by preparation of interpenetrating networks, which can be further extended to develop various kinds of multi-responsive smart materials.     

基于Berreman 4×4矩阵对胆甾相液晶Bragg反射带宽的模拟研究

利用Berreman 4×4矩阵和Matlab编程模拟了胆甾相液晶的反射光谱,分析了螺旋数(液晶厚度)、基板的折射率、双折射、折射率色散、固定螺距、梯度螺距和入射角等因素对反射光谱带宽的影响。结果表明,要得到理想的Bragg反射带宽,液晶层的厚度即螺旋数N需达到N≥10;基板折射率会影响最大反射率,基板折射率ng与寻常光折射率no相比,ngno时,最大反射率比较低,ng越小越影响明显,当ng≥no时,具有很好的反射率;折射率的色散和大的入射角会使带宽变窄,而大的双折射Δn和螺距P可以得到较宽的反射带宽,但拓宽效果有限。通过梯度螺距的函数表达式,理论模拟了具有螺距梯度的胆甾相液晶的反射带宽,其对于胆甾相液晶宽波反射的实验研究具有一定的意义。