摘要
通过测量扭曲液晶盒中的液晶分子的实际扭曲角及摩擦方向与液晶分子的界面指向矢之间的方位偏角,用自行建立的液晶方位表面锚定能的测量方法,测定了5CB液晶与摩擦的聚酰亚胺界面的锚定能及其温度依赖性,并用热力学理论进行了分析.实验结果表明,随着温度的增加液晶的表面锚定能Ea是减小的,从255℃时的50×10-5J/m2减小到35℃时的50×10-6J/m2;同时,外推长度de随温度的增加而增加,其与温度之间的关系为de=345[(Tc-T)T-1c]-045,在低于Tc05℃时de达到370nm;热力学理论的分析结果表明,在接近液晶的清亮点温度的准临界状态下,液晶(5CB)摩擦的聚酰亚胺界面附近的结构有序性对扭曲压力变得越来越敏感,而且其变化程度比液晶(5CB)SiO界面要大很多。
The surface anchoring of nematic liquid crystals is an important coefficient which expresses the effect of liquid crystal alignment and the mechanism of the surface alignment. The surface azimuthal anchoring energy can be obtained by measuring the twist angle in the twist cell and the surface torsional angle between the rubbing direction and the liquid crystal director at the substrate boundary. The temperature dependence of the surface anchoring energy at 5CB polyimide (PI) interface was studied. The surface anchoring energy decreases with increase of the temperature from 5 0×10 -5 J/m 2 at 25 5℃ to 5 0×10 -6 J/m 2 at 35 0℃. Meanwhile, the extrapolation length d e increases from 80nm at 25 5℃ to 370nm at 0 5℃ below T c. This result clearly signifies the important role of the ordered structure of the nematic interface in determining the temperature dependence of the anchoring strength at the 5CB PI interface.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
1996年第12期2035-2040,共6页
Acta Physica Sinica