Properties of the self-deforming Ntb phase in mesogenic dimers
Properties of the self-deforming Ntb phase in mesogenic dimers
复制标题
介晶二聚体中自变形 Ntb 相的特性
作者：
V. Panov;J. Vij;R. Balachandran;V. Borshch;O. Lavrentovich;M. Tamba;G. Mehl
会议将概述最近为揭示扭转弯曲向列Ntb相结构而进行的实验结果。这种新相提供了向列相的典型x射线衍射图，并且在奇链烃连接的介生二聚体中在低于传统向列相的温度下发现。Ntb相的材料在平行于摩擦方向的平面排列的摩擦晶胞中形成具有明确周期的自变形条纹。周期取决于单元格间距。在没有任何外部电磁场或厚度梯度的情况下出现自变形条纹。虽然材料由非手性分子组成，但低温向列相表现出几微秒级的快速线性光学响应。这种反应使人联想到具有手性的相。此外，在更高的场中，一些材料形成与光学响应方向相反的条纹域。这些条纹与摩擦方向垂直，其周期性取决于电压和频率。该相的fredericksz跃迁也表现出不同寻常的性质，并被证明是一级跃迁。表征这一相的技术包括偏振显微镜观察和光学对比光谱学。我们将讨论造成这种现象的可能原因。
An overview of the results obtained from the most recent experiments performed for revealing the structure of the twistbend nematic Ntb phase will be presented at the conference. This new phase provides typical X-ray diffraction pattern for the nematic phase and is found at temperatures below the conventional nematic phase in odd-chain hydrocarbon linked mesogenic dimers. The materials in the Ntb phase form self-deformed striped pattern parallel to the rubbing direction in planarly aligned rubbed cells with a well-defined period. The period is found to depend on the cell spacing. The selfdeformation stripes appear without any external electromagnetic field or thickness gradient across the cell. Although the materials are composed of non-chiral molecules, the low temperature nematic phase exhibits fast linear optical response of the order of a few microseconds. This response is reminiscent of the phase exhibiting chirality. Moreover, at higher fields some of the materials form striped domains with opposite direction of the optical response. These stripes appear normal to the rubbing direction and their periodicity depends on voltage and frequency. The Freedericksz transition in this phase also shows unusual properties and this is proven to be of the first order. The techniques to characterize this phase include polarized microscopy observation and optical contrast spectroscopy. Possible causes of the phenomena will be discussed.