Strong azimuthal anchoring energy at a nematic-polyimide interface
Strong azimuthal anchoring energy at a nematic-polyimide interface
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DOI：
10.1103/physreve.72.051708
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发表时间：
2005-11-01
影响因子：
2.4
通讯作者：
Marianelli, P
中科院分区：
文献类型：
--
作者：
Faetti, S;Marianelli, P
几年前，我们提出了一种自动反射测量方法来测量液晶和另一种介质之间界面处的指向矢方位角。该方法确保了很高的精度和灵敏度，几乎不受导演体失真的存在。后一种性质使得测量强锚定能成为可能。在本实验中，我们用这种方法测量了在摩擦聚酰亚胺层与液晶4-戊基-4（'）-氰基联苯（5CB）之间的方位角锚定能。这种接口的特点是由一个强大的方位锚定，因此，它代表了一个很好的测试所提出的反射法。一个交流平面电场被施加到一个介电层和随之而来的方位角旋转的界面处的董事进行测量。室温下的锚定能系数W-a较强（W-a= 0.33 × 10 ~（-3）J/m ~（2）），且随着接近清除温度而显著降低。的方位表面指向矢角的时间响应到一个逐步电场的证据的特征缓慢的动态，这是目前观察到的弱锚定基板。
Some years ago we proposed an automated reflectometric method to measure the director azimuthal angle at the interface between a nematic liquid crystal and another medium. The method ensures a great accuracy and sensitivity and is virtually unaffected by the presence of a director bulk distortion. This latter property makes it possible to measure strong anchoring energies. In the present experiment, we use this method to measure the azimuthal anchoring energy at the interface between the nematic liquid crystal 4-pentyl-4(')-cyanobiphenyl (5CB) and a rubbed polyimide layer. This kind of interface is characterized by a strong azimuthal anchoring and, thus, it represents a good test for the proposed reflectometric method. An ac planar electric field is applied to a nematic layer and the consequent azimuthal rotation of the director at the interface is measured. The anchoring energy coefficient W-a at room temperature is strong (W-a=0.33x10(-3) J/m(2)) and decreases greatly as the clearing temperature is approached. The time response of the azimuthal surface director angle to a stepwise electric field evidences the characteristic slow dynamics which is currently observed for weak anchoring substrates.