Theory of linear viscoelasticity of cholesteric liquid crystals
Theory of linear viscoelasticity of cholesteric liquid crystals
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胆甾型液晶的线性粘弹性理论
DOI：
10.1122/1.551112
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发表时间：
2000
影响因子：
3.3
通讯作者：
A. Rey
中科院分区：
文献类型：
--
作者：
A. Rey
小振幅振荡剪切流的棒状液晶的线性粘弹性的理论制定和应用到沿着流动，速度梯度和涡度方向的双螺旋线。零频率和无限频率的粘度的表达式推导和他们的排序预测。基于Miesowicz剪切粘度和扭矩系数各向异性的经典排序，发现最大（最小）的零频率粘度获得与螺旋沿着流动（梯度）方向。此外，零频和无限频粘度之间的差异被发现是敏感的螺旋取向，这样它是最大（最小）时，螺旋是沿着流动（梯度）方向。复数粘度对应于具有单个弛豫时间的粘弹性材料。松弛时间取决于变形中涉及的弗兰克弹性常数，使得当螺旋沿着涡度时，它是扭曲依赖的，否则是展曲弯曲的。当螺旋线沿着流动（梯度）方向时，粘弹性强度最大（最小）。硬杆理论的土井被用来确认预测的依赖性的粘弹性响应的强度上的螺旋取向。
The theory of linear viscoelasticity of rod-like cholesteric liquid crystals subjected to small-amplitude oscillatory shear flow is formulated and applied to the cholesteric helix along the flow, velocity gradient, and vorticity directions. Expressions for the zero- and infinite-frequency viscosities are derived and their ordering is predicted. Based on the classical ordering of the Miesowicz shear viscosities and anisotropies of torque coefficients, it is found that the largest (smallest) zero-frequency viscosity obtains with the helix along the flow (gradient) direction. In addition, the difference between the zero- and infinite-frequency viscosities is found to be sensitive to the helix orientation, such that it is largest (smallest) when the helix is along the flow (gradient) direction. The complex viscosity corresponds to a viscoelastic material with a single relaxation time. The relaxation time depends on the Frank elastic constants involved in the deformation, such that when the helix is along the vorticity it is twist dependent, and splay–bend otherwise. The strength of the viscoelasticity is largest (smallest) when the helix is along the flow (gradient) direction. The hard-rod theory of Doi is used to confirm the predicted dependence of the strength of the viscoelastic response on the cholesteric helix orientation.