Broadband reflective cholesteric liquid crystalline gels: volume distribution of reflection properties and polymer network in relation with the geometry of the cell photopolymerization
Broadband reflective cholesteric liquid crystalline gels: volume distribution of reflection properties and polymer network in relation with the geometry of the cell photopolymerization
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DOI：
10.1080/02678290701602876
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发表时间：
2007-09
期刊：
影响因子：
2.2
通讯作者：
S. Relaix;C. Bourgerette;M. Mitov
中科院分区：
文献类型：
--
作者：
S. Relaix;C. Bourgerette;M. Mitov
在光诱导制备CLC（CLC）凝胶期间，液晶（LC）组分的紫外（UV）光吸收特性可能会导致材料反射带宽的加宽，这种情况是由不对称照射条件（仅照射单元的一侧）促进的。原位结构的聚合物网络，包括在LC中，进行了研究，通过透射电子显微镜和温度依赖性的反射性能检查;它表明，网络具有结构梯度，是在起源的加宽现象。最小反射波长与UV光束进入的单元侧有关。先验地，这种情况是出乎意料的，因为它表明凝胶的这一部分富含无规（无限间距CLC）网络形成材料。结果进行了讨论的反射带特性与聚合物浓度的变化，这提供了间接访问的体积分布的周期性的机会。对于应用，宽带反射型光凝胶可能对反射型无偏振器显示器或具有智能电切换反射窗的光管理感兴趣。
The ultraviolet (UV) light‐absorbing properties of the liquid crystal (LC) constituent during the photo‐induced elaboration of a cholesteric LC (CLC) gel may induce the broadening of the reflection bandwidth of the material, a situation that is promoted by asymmetrical irradiation conditions (only one side of the cell is irradiated). The in situ structure of the polymer network, included in the LC, was investigated by transmission electron microscopy and the temperature dependence of the reflection properties examined; it is shown that the network has a structure gradient that is at the origin of the broadening phenomenon. The smallest reflection wavelength is related to the cell side from which the UV light beam came in. A priori, this situation was unexpected since it is shown that this part of the gel is enriched with nematic (infinite‐pitch CLC) network‐forming material. The result is discussed in relation to the variation of the reflection band characteristics with polymer concentration, which offers the opportunity for indirect access to the volume distribution of the cholesteric periodicities. For applications, broadband reflective cholesteric gels may be of interest for reflective polarizer‐free displays or for the light management with smart electrically‐switchable reflective windows.