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Smecticlike rheology and pseudolayer compression elastic constant of a twist-bend nematic liquid crystal
Physical Review Materials ( IF 3.4 ) Pub Date : 2020-11-16 , DOI: 10.1103/physrevmaterials.4.115601 M. Praveen Kumar , P. Kula , Surajit Dhara
Physical Review Materials ( IF 3.4 ) Pub Date : 2020-11-16 , DOI: 10.1103/physrevmaterials.4.115601 M. Praveen Kumar , P. Kula , Surajit Dhara
In twist-bend nematic () liquid crystals (LCs), the director (mean molecular orientation) exhibits heliconical structure with nanoscale periodicity. On the mesoscopic scale, resembles layered systems (like smectics) without a true mass density wave, where the helical pitch is equivalent to a “pseudolayer.” We study rheological properties of a phase and compare the results with those of a usual smectic- phase. Analyzing the shear response and adapting a simplified physical model for the rheology of defect-mediated lamellar systems, we measure the pseudolayer compression elastic constant of the phase from the measurements of the dynamic modulus . It is found that of the phase is in the range of – Pa and it follows a temperature dependence, , as predicted by the recent coarse-grained elastic theory. Our results show that the structural rheology of LCs is strikingly similar to that of the usual smectic LCs, although the temperature dependence of is much faster than that of smectic LCs as predicted by the coarse-grained models.
中文翻译:
扭曲弯曲向列液晶的类膜流变学和伪层压缩弹性常数
在扭曲向列(液晶(LCs)时,指向矢(平均分子取向)显示出具有纳米级周期性的螺旋结构。在介观尺度上类似于没有真正质量密度波的分层系统(例如叠层管),其中螺旋螺距等效于“伪层”。我们研究了a的流变特性 阶段,并将结果与通常的近晶相比较相。分析剪切响应并为缺陷介导的层状体系的流变性采用简化的物理模型,我们测量伪层压缩弹性常数 的 动态模量测量的相位 。发现 的 相位在 – Pa随温度变化, ,正如最近的粗粒度弹性理论所预测的那样。我们的结果表明,结构流变学 LC与通常的近晶LC非常相似,尽管 正如粗粒度模型所预测的,它比近晶LC快得多。
更新日期:2020-11-16
中文翻译:
扭曲弯曲向列液晶的类膜流变学和伪层压缩弹性常数
在扭曲向列(液晶(LCs)时,指向矢(平均分子取向)显示出具有纳米级周期性的螺旋结构。在介观尺度上类似于没有真正质量密度波的分层系统(例如叠层管),其中螺旋螺距等效于“伪层”。我们研究了a的流变特性 阶段,并将结果与通常的近晶相比较相。分析剪切响应并为缺陷介导的层状体系的流变性采用简化的物理模型,我们测量伪层压缩弹性常数 的 动态模量测量的相位 。发现 的 相位在 – Pa随温度变化, ,正如最近的粗粒度弹性理论所预测的那样。我们的结果表明,结构流变学 LC与通常的近晶LC非常相似,尽管 正如粗粒度模型所预测的,它比近晶LC快得多。