Leys Jan, Glorieux Christ, Thoen Jan
Laboratorium voor Akoestiek en Thermische Fysica, Departement Natuurkunde en Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D-bus 2416, Leuven, Belgium.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Jun;77(6 Pt 1):061707. doi: 10.1103/PhysRevE.77.061707. Epub 2008 Jun 17.
The dielectric response of liquid crystals in their nematic phase shows an acceleration of the relaxation associated with the rotation around the short molecular axis when dispersed with aerosils. However, in the isotropic phase, this acceleration is only seen for certain liquid crystalline molecules. In this paper, an associating liquid crystal (5CB) and a shorter monotropic liquid crystalline member of the same homologous series (4CB), a liquid crystal that does not show association (5NCS) and a nonassociating liquid crystal (5O5) have been studied by dielectric spectroscopy in the isotropic phase. Both 4CB and 5CB show a constant acceleration in the isotropic phase, observed over a broad temperature range. 5NCS and 5O5 do not show an acceleration in their isotropic phase. It seems that the disturbance of the dipole-dipole association process for the associating molecules is an important factor in the explanation of the acceleration of the relaxation in the isotropic phase.
液晶向列相的介电响应表明，当与气相二氧化硅分散时，与围绕短分子轴旋转相关的弛豫会加速。然而，在各向同性相，这种加速仅在某些液晶分子中可见。本文通过介电谱研究了一种缔合液晶（5CB）、同一同系物系列中较短的单向性液晶成员（4CB）、一种不显示缔合的液晶（5NCS）和一种非缔合液晶（5O5）在各向同性相中的情况。4CB和5CB在各向同性相中均表现出恒定的加速，这在很宽的温度范围内都能观察到。5NCS和5O5在各向同性相中未表现出加速。对于缔合分子而言，偶极 - 偶极缔合过程的扰动似乎是解释各向同性相中弛豫加速的一个重要因素。
