Deformation and relaxation processes of mono- and bilayer domains of liquid crystalline Langmuir films on water
Deformation and relaxation processes of mono- and bilayer domains of liquid crystalline Langmuir films on water
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DOI：
10.1021/la960617n
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发表时间：
1996-11-13
期刊：
影响因子：
3.9
通讯作者：
Fuller, GG
中科院分区：
文献类型：
--
作者：
Lauger, J;Robertson, CR;Fuller, GG
本文采用伸展流场和布鲁斯特角显微镜同时测量的方法，研究了热致液晶在空气-水界面处单层和双层畴的流动变形和弛豫。在扩展流中，单层和双层结构域被扭曲成长而稳定的弦状结构域。这是由于在二维情况下不存在瑞利不稳定性，否则会导致在三维情况下发生破裂机制。然而，区域厚度的微小波动会导致缺陷，从而导致弦区域的破裂，然后由于线张力效应导致两个区域末端的收缩。在高变形波状区和小变形区弛豫实验中，测定了单层和双层畴的线张力。两种变形情况下，单层和双层情况下的线张力值相同。然而，发现双分子层的线张力比单分子层高约10倍。人们认为，这种巨大的差异是指间双分子层中具有很强吸引力的偶极-偶极相互作用力的结果。
Flow deformation and relaxation of mono- and bilayer domains of a thermotropic liquid crystal at the air-water interface have been studied by means of simultaneous application of extensional flow fields and Brewster angle microscopy measurements. In an extentional flow, mono- and bilayer domains are found to be distorted into long, stringlike domains that are stable. This is due to the absence of Rayleigh instabilities in the two-dimensional case, which otherwise lead to the occurrence of a break-up mechanism in three dimensions. However, small fluctuations in the domain thickness lead to defects that can cause breakup of the string domains followed by a retraction of the two domain ends due to line tension effects. In relaxation experiments covering both the high deformation bola-shaped regime and the small-deformation regime of slightly deformed domains, the line tensions of mono- and bilayer domains were determined. Both deformation regimes yielded the same values ibr the line tension of the mono- and bilayer cases. However, the line tension of the bilayer was found to be about 10 times higher than that of the monolayer. It is believed that this large difference is a result of a strong attractive dipole-dipole interaction force in the interdigitated bilayer.