The twist bend nematic: a case of mistaken identity
The twist bend nematic: a case of mistaken identity
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DOI：
10.1080/02678292.2020.1795943
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发表时间：
2020-09-10
期刊：
影响因子：
2.2
通讯作者：
Photinos, Demetri J.
中科院分区：
文献类型：
--
作者：
Samulski, Edward T.;Vanakaras, Alexandros G.;Photinos, Demetri J.
我们回顾了迈耶猜想的物理原理，即宏观尺度的扭曲和弯曲如何在向列相的 Frank-Oseen 弹性理论中共同作用，从而创建单轴、非极性向列指向矢的螺旋排列，即所谓的“扭曲弯曲向列”N-TB。我们发现，自 2011 年以来，在 Toriumi 发现的奇怪的亚甲基连接的氰基联苯二聚体中观察到的第二个低温向列相（称为 N-X）已被错误地识别为 N-TB。此外，随着更多关于 N(X) 的定量数据的出现，迈耶的简单预测已被扭曲以适应这些发现。事实上，N(X)相的分子组织符合N(PT)相，这是一种2016年提出的非线性介晶的极性、扭曲排列。N(PT)的属性被总结并与N(TB)的属性区分开来，以期有助于更好地理解N(X)相，同样重要的是，鼓励研究人员继续寻找一种能够展现Meyer开创性理论建议的液晶，即形式手性可以存在于由非手性分子组成的简单向列相中。
We review the physics underlying Meyer's conjecture of how macroscopic-scale twist and bend conspire within the Frank-Oseen elasticity theory of nematics to create a heliconical arrangement of the uniaxial, apolar nematic director, the so-called 'twist bend nematic' N-TB. We show that since 2011 a second, lower-temperature nematic phase observed in odd methylene-linked cyanobiphenyl dimers discovered by Toriumi and called N-X, has been incorrectly identified as N-TB. Moreover, as more quantitative data on the N(X)emerged, Meyer's simple prediction has been distorted to accommodate those findings. In fact, the molecular organisation in the N(X)conforms to the N(PT)phase, a polar, twisted arrangement of nonlinear mesogens advanced in 2016. The attributes of the N(PT)are summarised and differentiated from those of the N(TB)in an effort to contribute to a better understanding of the N(X)phase and, equally important, to encourage researchers to continue to search for a liquid crystal that exhibits Meyer's pioneering theoretical suggestion, namely that form-chirality can exist in simple nematics composed of achiral molecules.