Kishi Wakako, Iwata Naoto, Furumi Seiichi
Department of Chemistry, Graduate School of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan.
Molecules. 2025 Jul 2;30(13):2839. doi: 10.3390/molecules30132839.
Ethyl cellulose (EC) and its derivatives are known to exhibit the cholesteric liquid crystal (CLC) phase with visible light reflection in a lyotropic manner after adding appropriate solvents. Generally, the reflection peak of conventional CLCs is easily wavelength shifted by temperature. However, our previous study showed that the reflection wavelength can be maintained even after heating for the lyotropic CLCs of completely pentyl-etherified EC derivatives with methacrylic acid (MAA). However, the emergence of thermally stable reflection colors still remains obscure in the mechanism at the mesoscopic scale. In this study, we evaluated the temperature dependence of the reflection wavelength for the lyotropic CLCs of a series of completely etherified EC derivatives possessing different alkoxy chains by addition of MAA. It was found that butyl- or pentyl-etherified EC derivatives are suitable for preparation of the lyotropic CLCs with visible Bragg reflection, whereas visible light reflection cannot be observed for the other mixtures of propyl- and hexyl-etherified EC derivatives with MAA. Furthermore, it turned out that lyotropic CLCs of pentyl-etherified EC derivatives with MAA show the smallest temperature dependence of their reflection wavelength. Based on the results of ultra-small-angle X-ray scattering (USAXS) and small-angle X-ray scattering (SAXS) measurements of CLC films, we presumed that the emergence of thermally stable reflection colors from the lyotropic CLCs of pentyl-etherified EC derivatives with MAA arises from their phase separation at the mesoscopic scale by changing the temperature.
已知乙基纤维素（EC）及其衍生物在添加适当溶剂后会以溶致方式呈现胆甾相液晶（CLC）相并伴有可见光反射。一般来说，传统CLC的反射峰很容易随温度发生波长偏移。然而，我们之前的研究表明，对于完全戊基醚化的EC衍生物与甲基丙烯酸（MAA）形成的溶致CLC，即使加热后反射波长仍可保持。然而，在介观尺度上，热稳定反射颜色出现的机制仍不清楚。在本研究中，我们通过添加MAA评估了一系列具有不同烷氧基链的完全醚化EC衍生物的溶致CLC的反射波长对温度的依赖性。结果发现，丁基或戊基醚化的EC衍生物适合制备具有可见光布拉格反射的溶致CLC，而丙基和己基醚化的EC衍生物与MAA的其他混合物则无法观察到可见光反射。此外，结果表明，戊基醚化的EC衍生物与MAA形成的溶致CLC的反射波长对温度的依赖性最小。基于对CLC薄膜的超小角X射线散射（USAXS）和小角X射线散射（SAXS）测量结果，我们推测戊基醚化的EC衍生物与MAA形成的溶致CLC中热稳定反射颜色的出现是由于温度变化导致其在介观尺度上发生相分离。
