Thermal control of transmittance/diffraction states of holographic structures composed of polymer and liquid crystal phases
Thermal control of transmittance/diffraction states of holographic structures composed of polymer and liquid crystal phases
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DOI：
10.1016/j.solmat.2010.05.040
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发表时间：
2010-10-01
影响因子：
6.9
通讯作者：
Ogiwara, Akifumi
中科院分区：
文献类型：
--
作者：
Kakiuchida, Hiroshi;Tazawa, Masato;Ogiwara, Akifumi
利用光致相分离技术制备了一种由聚合物和液晶相组成的微周期结构——全息聚合物分散液晶（HPDLC）。预计HPDLC可以用作热驱动光控制器，特别是用于自主太阳射线控制窗口，该窗口利用周期结构LC相中的向列向各向同性（N-I）相变现象。在本研究中，研究了具有不同热行为的样品的透射/衍射特性，发现在30℃左右，15%的太阳辐射作为温度的函数在透射和衍射状态之间切换，并展示了将HPDLC用于太阳射线控制窗口的更实用的解决方案。从结构分析的角度来看，扫描电镜显示，几十纳米大小的LC液滴分布、聚结形成周期性的LC层。通过偏光显微镜和透射率/衍射测量，观察到液滴中的LC分子沿光栅矢量取向强烈，且取向随温度升高而下降。这些观察到的结构对于产生由于N-I跃迁而导致的透射率/衍射性质的大变化具有重要意义。(C) 2010 Elsevier B.V.版权所有
A microperiodic structure composed of polymer and liquid crystal (LC) phases, called holographic polymer dispersed liquid crystal (HPDLC), was fabricated by a photo-induced phase-separation technique. It is anticipated that the HPDLC can be used as a thermo-driven light controller, in particular, for an autonomous solar-ray control window, which utilizes the nematic-to-isotropic (N-I) phase transition phenomenon in the LC phase of the periodic structure. In the present study, the transmittance/diffraction properties of samples with different thermal behaviors were examined, and it was found that 15% of the solar radiation was switched between the transmittance and diffraction states as a function of temperature at around 30 degrees C. Furthermore, a more practical solution for using the HPDLC for a solar-ray control window was demonstrated. From the viewpoint of structural analysis, scanning electron microscopy reveals that LC droplets, a few tens of nanometers in size are, distributed and coalesce to form periodic LC layers. By carrying out polarizing microscopy and performing transmittance/diffraction measurements as a function of temperature, it is observed that the LC molecules in the droplets are strongly oriented along the grating vector and their orientations decline with a rise in temperature. These observed structures are of importance for the generation of a large change in the transmittance/diffraction properties due to N-I transition. (C) 2010 Elsevier B.V. All rights reserved.