[论文解读] Rheological properties and shear-induced structures of ferroelectric nematic liquid crystals

Ashish Chandra Das, Sathyanarayana Paladugu+1 more|arXiv (Cornell University)|Feb 26, 2026

Liquid Crystal Research Advancements被引用 0

一句话总结

该论文研究剪切流如何在多种材料与相中影响铁电向列相液晶的极化、粘度和微观结构，揭示流动区间和剪切依赖的粘度。

ABSTRACT

Recently discovered ferroelectric nematic (NF) liquid crystals are fluids with a polar orientational order. The electric polarization vector can be aligned by an electric field and by surface anchoring. Here, we explore how the polarization field and effective viscosity of the NF materials are affected by shear flows. We explore three NF materials, abbreviated RM734, DIO, and a room-temperature FNLC919, all of which exhibit a paraelectric nematic (N) and the NF phase. All materials show an increase of the viscosity upon cooling, with an Arrhenius behavior. In DIO and FNLC919, the antiferroelectric SmZA phase shows a strong dependence of the effective viscosity on the shear rate: this viscosity is lower than the viscosity of the N and NF phases at high shear rates but is much higher when the shear rate is low. The behavior is associated with the layered structure of the SmZA phase. All mesophases exhibit shear-thinning behavior at low shear rates and a nearly Newtonian behavior at higher shear rates. In terms of alignment, we observe three regimes in the N and NF phases: flow-alignment at low shear rates, log-rolling regime with the director and polarization along the vorticity axis at high shear rates, and polydomain structures at intermediate rates. In the flow-aligning regime, the NF polarization does not tilt away from the shear direction, which is in sharp contrast to the flow-induced tilt of the N director. The effect is attributed to the avoidance of splay deformations and associated space charge in the flowing NF. The temperature and shear rate dependencies of the viscosity and the uncovered shear-induced structural effects of NF advance our understanding of these materials and potentially facilitate their applications.

研究动机与目标

• 理解铁电向列液体（NF）在剪切流作用下极化与有效粘度的响应。
• 表征在副极性向列相（N）、NF 与 SmZA 反铁电相中的粘度行为。
• 识别并描述 NF 材料中剪切速率依赖的结构与取向区间。
• 考察表面锚定和电极化与流动相互作用对流变学的影响。

提出的方法

• 实验测量三种 NF 材料在温度和剪切速率下的粘度及其依赖性。
• 识别包括 N、NF、SmZA 的相序并评估它们的流变响应。
• 表征在不同剪切速率下的流动区间与取向（director/polarization）对齐。
• 分析 NF 在流动中的张角形变和空间电荷的作用，以解释流向对齐行为。
• 将 NF 行为与副极性向列 N 进行比较，以阐明极化对流变学的影响。

实验结果

研究问题

• RQ1 剪切流如何影响不同相（N、NF、SmZA）中 NF 材料的粘度？
• RQ2 NF 与 N 相中在剪切下的不同对齐区间（流向对齐、横滚、聚域）有哪些？
• RQ3 NF 的极化相较于 N 相中的 director 对流动有何响应差异？
• RQ4 在 SmZA 相中剪切下产生的结构变化及其对流变学的影响？
• RQ5 为何 NF 相较于 N 在流动下呈现不同的粘度依赖，尤其在避免空间电荷方面？

主要发现

• 粘度在降温过程中呈阿伦尼乌斯行为上升，适用于所有材料。
• 在 DIO 与 FNLC919 中，SmZA 显示强烈的剪切速率依赖性粘度，在高剪切时较低，在低剪切时显著更高，与其层状结构相关。
• 所有相态在低剪切下表现为剪切变稀，在高剪切近似牛顿流动。
• N 与 NF 的三种流动区间：低剪切时的流向对齐、中等剪切时的聚域化、以及高剪切时的对流滚动。
• NF 的极化在流向对齐区间倾向于与流向保持一致，与 N 相取向的倾斜不同，暗示 NF 中在流动时避开张角变形与空间电荷。