Cholesteric liquid crystalline materials reflecting more than 50% of unpolarized incident light intensity
Cholesteric liquid crystalline materials reflecting more than 50% of unpolarized incident light intensity
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DOI：
10.1080/02678290601116175
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发表时间：
2007-02-01
期刊：
影响因子：
2.2
通讯作者：
Dessaud, Nathalie
中科院分区：
文献类型：
--
作者：
Mitov, Michel;Dessaud, Nathalie
胆甾相液晶（CLCs）在波长与螺旋螺距相匹配时选择性反射光。反射率被限制在50%的环境，非偏振光，因为只有圆偏振光与螺旋相同的手性被反射。本文报道了一种光学特性超过50%反射率极限的CLC凝胶的制备过程和性能。将可光聚合的单体引入到具有热诱导螺旋反转的CLC体积中，然后在螺旋为右旋时用紫外光固化共混物。在反应前具有相同螺距但具有左旋感的胆甾螺旋温度下测量，反射率超过50%。研究了其在红外区的反射特性。扫描电镜研究表明，中间相的组织转移到网络的结构上。凝胶结构是由含有两个低摩尔质量LC分子居群的螺旋结构聚合物网络组成的。它们每一种的特点都是有选择性反射的圆偏振光带。光响应随温度变化的监测为区分LC分子的束缚部分和自由部分对反射率的贡献提供了机会，并提供了从固化温度开始温度降低时反射通量逐渐增加的证据。提供了在整个光通量范围内调制反射的新机会。潜在的应用与智能窗口或具有更大反射率水平的无反射偏光板显示器的光管理有关。
Cholesteric liquid crystals ( CLCs) selectively reflect light when the wavelength matches the helical pitch. The reflectance is limited to 50% of ambient, unpolarized light because only circularly polarized light of the same handedness as the helix is reflected. Here the elaboration procedure and the properties of a CLC gel whose optical characteristics go beyond the 50% reflectance limit are reported. Photopolymerizable monomers are introduced into the volume of a CLC exhibiting a thermally induced helicity inversion and the blend is then cured with UV light when the helix is right- handed. The reflectance exceeds 50% when measured at the temperature assigned at a cholesteric helix with the same pitch but a left- handed sense before reaction. The reflection properties are investigated in the infrared region. From scanning electron microscopy investigations, it is shown that the organization of the mesophase is transferred onto the structure of the network. The gel structure is discussed as consisting of a polymer network with a helical structure containing two populations of low molar mass LC molecules. Each of them is characterized by a band of circularly polarized light which is selectively reflected. The monitoring of the optical response with temperature offers the opportunity to discriminate the respective contributions of the bound and free fractions of LC molecules to the reflectance, and to give evidence of the progressive increase of the reflected flux when the temperature decreases from the curing temperature. Novel opportunities to modulate the reflection over the whole light flux range are offered. Potential applications are related to the light management for smart windows or reflective polarizer- free displays with a larger scale of reflectivity levels.