Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA.
Phys Rev Lett. 2009 Dec 4;103(23):237803. doi: 10.1103/PhysRevLett.103.237803.
We have found that bent-core liquid crystalline materials show exceptionally large intrinsic flow birefringence in their isotropic liquid phase. This effect is more than 100 times larger than typical values measured for low molecular weight liquid crystals. The specific flow birefringence (i.e., normalized by the flow viscosity) is an order of magnitude larger than in both side-chain polymeric as well as low molecular weight liquid crystals. We propose that this large enhancement for bent-core compounds may be attributed to nanoscale smecticlike clusters that persist above the nematic-isotropic transition temperature, and shear align under shear flow; however, this mechanism has not yet been definitively confirmed.
我们发现，双轴各向异性液晶材料在各向同性液相中表现出异常大的固有流动双折射。这种效应比测量的低分子液晶的典型值大 100 多倍。特定的流动双折射（即，通过流动粘度归一化）比侧链聚合物和低分子液晶都大一个数量级。我们提出，双轴各向异性化合物的这种大幅度增强可能归因于在向列-各向同性转变温度以上仍然存在的纳米级类似向列层状的簇，并且在剪切流动下沿剪切方向排列；然而，这种机制尚未得到明确证实。
