Side Chain Effect of Hydroxypropyl Cellulose Derivatives on Reflection Properties
Side Chain Effect of Hydroxypropyl Cellulose Derivatives on Reflection Properties
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DOI：
10.3390/polym11101696
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发表时间：
2019-10-01
期刊：
影响因子：
5
通讯作者：
Furumi, Seiichi
中科院分区：
文献类型：
--
作者：
Hayata, Kenichiro;Furumi, Seiichi
已知一些纤维素衍生物通过改变侧链和分别与特定溶剂混合而呈现具有可见反射特征的热致和溶致液晶（CLC）相。虽然到目前为止已有许多研究报道，但大多数衍生物的侧链都是线性烷基，而不是庞大的苯基。在这篇报告中，我们合成了一系列的羟丙基纤维素（HPC）衍生物，同时具有线性丙酰基酯和庞大的（三氟甲基）苯基氨基甲酸酯的侧链。由于CLC螺距的增加，加热后HPC衍生物的反射峰向更长的波长移动。这种反射峰的热致位移行为不仅与丙酰化程度有关，而且与HPC衍生物侧链上的取代基有关。当HPC的侧链用丙酰基酯和大体积取代基如3，5-双（三氟甲基）苯基氨基甲酸酯进行化学修饰时，在相同温度下在较长波长处出现反射峰。这可能是因为庞大的侧链的空间位阻，支持的经验分子模拟计算。虽然（三氟甲基）苯基的占据体积与具有可见布拉格反射的CLC相温度无关，但是取代基位置，即，三氟甲基的取代基取向影响CLC相温度。此外，我们还发现HPC侧链中氨基甲酸酯部分之间的氢键在热诱导反射峰的位移中起着重要的作用。
Some cellulose derivatives are known to exhibit thermotropic and lyotropic cholesteric liquid crystal (CLC) phases with a visible reflection feature by changing the side chains and mixing with specific solvents, respectively. Although many studies have been reported so far, most of the derivatives have the side chains of linear alkyl groups, but not the bulky phenyl groups. In this report, we synthesized a series of hydroxypropyl cellulose (HPC) derivatives that possessed both linear propionyl esters and bulky (trifluoromethyl)phenyl carbamates in the side chains. The reflection peaks of HPC derivatives shifted to longer wavelengths upon heating due to an increase in the CLC helical pitch. Such thermally induced shifting behavior of the reflection peak was crucially dependent on not only the propionyl esterification degree, but also the substituents in the side chains of HPC derivatives. When the side chains of HPC were chemically modified with both propionyl esters and bulky substituents such as 3,5-bis(trifluoromethyl)phenyl carbamates, the reflection peaks emerged at longer wavelengths at the same temperature. This probably happened because of the steric hindrance of bulky side chains, as supported by the empirical molecular modeling calculation. Although the occupied volumes of (trifluoromethyl)phenyl groups were independent of the CLC phase temperature with visible Bragg reflection, the substituent position, i.e., substituent orientation of trifluoromethyl groups affected the CLC phase temperature. Moreover, we found that the hydrogen bonds between carbamate moieties in the HPC side chains play an important role in the thermally induced shift of reflection peaks.