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.

中文翻译：

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用微流变学探测弯曲核向列型液晶中的近晶簇。

由于在向列相中存在近晶团簇（称为“ cycyactic”团簇），许多弯曲核向列液晶表现出不同寻常的物理性能。在这里，我们使用微流变技术研究了这些簇对两个不对称弯曲核液晶的复数剪切模量（G *（ω））的影响。具有较短烃链（8OCH化合物₃）仅表现出向列型（N）的相位，而具有较长的链（16OCH化合物₃）既表现出向列型（N）和近晶A（SMA）相。流变结果与曲率弹性常数的测量相关。我们的结果表明，16OCH ₃的定向剪切模量由于近晶团簇，刚好在SmA到N相转变温度之上的，与8OCH ₃明显不同。使用一个简单的模型来估计群集的近似大小。因此，对弯曲核向列型液晶的微流变学研究对于提取有关潜在近晶簇的信息非常有用。