A surface forces platform for dielectric measurements
A surface forces platform for dielectric measurements
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用于介电测量的表面力平台
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
S. Granick
中科院分区：
文献类型：
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作者：
Yoon‐Kyoung Cho;S. Granick
描述了通过使用云母背面上的银片作为电极在表面力设备内实现介电谱（频率范围10 - 1-106 Hz）的方法。在25 °C的实验温度下，利用这些方法研究了表面取向、约束和剪切场对5-氰基联苯（5 CB）液晶的竞争效应。 在平面取向中，薄膜可以被挤压到分子厚度的最小厚度。在垂直（垂面）取向中，膜可以被挤压到5CB二聚体的预期厚度。很难定量讨论f>105 Hz时的响应，因为在实验频率窗口中看不到峰值。尽管如此，平面取向的分子的松弛模式的发病出现在更高的频率比垂直取向。一个较慢的弛豫模式，峰值在f = 10 Hz，被分配给电极极化，由于迁移率的…
Methods are described to implement dielectric spectroscopy (frequency range 10−1–106 Hz) within a surface forces apparatus by using as electrodes silver sheets on the backside of mica. These methods are applied to study the competitive effects of surface alignment, confinement, and shear field on 5CB (5-cyanobiphenyl), a nematic liquid crystal at the experimental temperature of 25 °C. In the planar orientation, films could be squeezed to a minimum thickness of ≈5 A, the molecule’s thickness. In the perpendicular (homeotropic) orientation, films could be squeezed to ≈25 A, the expected thickness of the head-to-tail 5CB dimer. It was difficult to discuss responses at f>105 Hz quantitatively because the peak was not visible in the experimental frequency window. Nonetheless, the onset of the relaxation mode for the planar oriented molecules appears at higher frequency than for the homeotropic orientation. A slower relaxation mode, peaked at f≈10 Hz, was assigned to electrode polarization due to the mobility o...