Dependence of the dynamic moduli of heterogeneous nematic polymers on planar anchoring relative to flow direction
Dependence of the dynamic moduli of heterogeneous nematic polymers on planar anchoring relative to flow direction
复制标题
异质向列聚合物的动态模量对相对于流动方向的平面锚定的依赖性
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
M. Forest
中科院分区：
文献类型：
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作者：
Eric P. Choate;M. Forest
我们通过 Doi-Marrucci-Greco 取向张量公式分析了平行板振荡剪切实验中向列聚合物的动态模量，特别关注流变特性与壁锚固条件之间的内在联系。我们假设标准实验程序，其中板已被摩擦以实现平行于摩擦方向的强向列锚定。我们推导了向列液体在线性粘弹性弱振荡剪切状态下的异质谐波响应。响应函数由定向锚定条件参数化，特别是由摩擦方向和流动方向之间的旋转角度参数化。从这个分析中，我们读出了频率相关的存储模量和损耗模量。主要影响在于储能模量，其中与涡量轴对齐的高频摩擦会导致 G' 比流动方向上的摩擦大两到三个数量级。这种锚定依赖性显示了基于张量的模型的阶参数波动的重要性：莱斯利-埃里克森理论预测涡度对齐锚定的零存储模量。对于低频，尽管我们预测涡度对齐锚定的模量非零，但这种效应与流对齐锚定以类似于莱斯利-埃里克森理论的方式最大化 G' 相反。
We analyze the dynamic moduli of nematic polymers in a parallel plate oscillatory shear experiment from a Doi–Marrucci–Greco orientation tensor formulation, paying special attention to the inherent connection between rheological properties and wall anchoring conditions. We assume standard experimental procedures in which the plates have been rubbed to achieve strong nematic anchoring parallel to the rubbing direction. We derive the heterogeneous, harmonic response of the nematic liquid in the weak oscillatory shear regime of linear viscoelasticity. The response function is parameterized by the orientational anchoring condition and, in particular, by the angle of rotation between the rubbing direction and the flow direction. From this analysis, we read off the frequency-dependent storage and loss moduli. The dominant effect is in the storage modulus where for high frequencies rubbing aligned with the vorticity axis can cause G′ to be two to three orders of magnitude larger than rubbing in the flow direction. This anchoring dependency shows the significance of the order parameter fluctuations of tensor-based models: the Leslie–Ericksen theory predicts zero storage modulus for vorticity-aligned anchoring. For low frequencies, this effect is reversed with flow-aligned anchoring maximizing G′ in a manner similar to the Leslie–Ericksen theory although we predict a nonzero modulus for vorticity-aligned anchoring.