Enhanced conductivity and dielectric absorption in discotic liquid crystalline columnar phases of a vanadyl complex
Enhanced conductivity and dielectric absorption in discotic liquid crystalline columnar phases of a vanadyl complex
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氧钒络合物盘状液晶柱状相的电导率和介电吸收增强
DOI：
10.1080/02678290110093741
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发表时间：
2002
期刊：
影响因子：
2.2
通讯作者：
S. Wróbel
中科院分区：
文献类型：
--
作者：
W. Haase;D. Kilian;M. Athanassopoulou;D. Knawby;T. Swager;S. Wróbel
通过 DSC、偏光光学显微镜、反转电流技术、X 射线衍射和频域介电谱研究了液晶氧钒络合物。该化合物呈现出三种柱状相：矩形有序（Colro）、矩形无序（Colrd）和六方无序（Colhd），所有这些都在低频下表现出介电弛豫过程。在 Colro 低温阶段，该过程似乎与柱内极化聚合物链的缓慢松弛有关（mHz 频率范围）。然而，在 Colhd 高温无序相中，这种弛豫速度更快（Hz 范围）。有趣的是，所研究的液晶相显示出增强的电导率，电导率变化了四个数量级，从定向无序晶体（ODIC 相）中的 10−9 S m−1 到 Colhd 高温相中的 10−5 S m−1 。这种电导率值对于半导体材料来说是典型的。
A liquid crystalline vanadyl complex has been studied by DSC, polarizing optical microscopy, the reversal current technique, X-ray diffraction and frequency domain dielectric spectroscopy. The compound exhibits three columnar phases: rectangular ordered (Colro), rectangular disordered (Colrd), and hexagonal disordered (Colhd), all of which show a dielectric relaxation process at low frequencies. In the Colro low temperature phase this process seems to be connected with a slow relaxation of polarized polymeric chains inside the columns (mHz frequency range). However, in the Colhd high temperature disordered phase this relaxation is faster (Hz range). It is interesting that the liquid crystalline phases studied show enhanced conductivity which changes by four orders of magnitude from 10−9 S m−1 in the orientationally disordered crystal (an ODIC phase) to 10−5 S m−1 in the Colhd high temperature phase. Such a value of the conductivity is typical for semiconducting materials.