Paladugu Sathyanarayana, Kaur Supreet, Mohiuddin Golam, Pujala Ravi Kumar, Pal Santanu Kumar, Dhara Surajit
School of Physics, University of Hyderabad, Hyderabad, India.
Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector-81, Knowledge City, Manauli 140306, India.
Soft Matter. 2020 Aug 19;16(32):7556-7561. doi: 10.1039/d0sm00796j.
Many bent-core nematic liquid crystals exhibit unusual physical properties due to the presence of smectic clusters, known as "cybotactic" clusters, in the nematic phase. Here, we investigate the effect of these clusters on the complex shear modulus (G*(ω)) of two asymmetric bent-core liquid crystals using a microrheological technique. The compound with a shorter hydrocarbon chain (8OCH3) exhibits only a nematic (N) phase whereas the compound with a longer chain (16OCH3) exhibits both nematic (N) and smectic-A (SmA) phases. The rheological results are correlated with the measurements of curvature elastic constants. Our results show that the directional shear modulus of 16OCH3, just above the SmA to N phase transition temperature, is strikingly different than that of 8OCH3, owing to the smectic clusters. An approximate size of the clusters is estimated using a simple model. Therefore, microrheological studies on bent-core nematic liquid crystals are very useful in extracting information about underlying smectic clusters.
许多弯曲核向列型液晶由于在向列相中存在近晶簇（称为“近晶有序”簇）而表现出异常的物理性质。在此，我们使用微观流变技术研究了这些簇对两种不对称弯曲核液晶的复剪切模量（G*(ω)）的影响。具有较短烃链（8OCH3）的化合物仅表现出向列相（N），而具有较长链（16OCH3）的化合物则表现出向列相（N）和近晶A相（SmA）。流变学结果与曲率弹性常数的测量相关。我们的结果表明，由于近晶簇的存在，16OCH3在略高于SmA向N相转变温度时的定向剪切模量与8OCH3的显著不同。使用一个简单模型估计了簇的近似尺寸。因此，对弯曲核向列型液晶的微观流变学研究对于提取有关潜在近晶簇的信息非常有用。
