Liquid crystal elastomers (LCEs) are a class of smart elastomers exhibiting unusual mechanical behavior, including large energy dissipation and soft elasticity under uniaxial tensile loading. LCEs are composed of liquid crystal molecules, called mesogens, linked by a network of polymer chains. During deformation, the mesogens orient in the direction of the loading, leading to soft elasticity, which is an increase in strain at constant stress. The combination of mesogen rotation and intrinsic polymer viscoelasticity leads to a nonlinear viscoelastic soft elastic behavior. The aim of this paper is to investigate the coupling between the viscoelastic mechanisms and soft elasticity in main chain LCEs. We propose a rheological model in which the mesogen rotation during deformation is represented by a reversible slider while viscoelastic relaxation mechanisms are modeled as series of Maxwell elements coupled or decoupled with mesogen rotation. Fitting this model to experimental data demonstrate that the coupling between polymer chain viscoelasticity and mesogen rotation is partial, the long-time relaxation mechanisms are coupled and the short-time relaxation mechanisms are decoupled from mesogen rotation. Furthermore, we show that the viscosity of mesogen rotation is not necessary to properly predict the elastic modulus during the soft elasticity but it is needed to properly predict the initiation of the phenomenon.

中文翻译：

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主链向列液晶弹性体粘弹性与软弹性的耦合

液晶弹性体（LCE）是一类智能弹性体，表现出不寻常的机械行为，包括单轴拉伸载荷下的大能量耗散和软弹性。 LCE 由称为介晶的液晶分子组成，通过聚合物链网络连接。在变形过程中，介晶沿载荷方向取向，导致软弹性，即恒定应力下应变的增加。介晶旋转和固有聚合物粘弹性的结合导致非线性粘弹性软弹性行为。本文的目的是研究主链 LCE 中粘弹性机制和软弹性之间的耦合。我们提出了一种流变模型，其中变形期间的介晶旋转由可逆滑块表示，而粘弹性松弛机制被建模为一系列与介晶旋转耦合或解耦的麦克斯韦元件。将该模型与实验数据进行拟合表明，聚合物链粘弹性与介晶旋转之间的耦合是部分的，长时弛豫机制是耦合的，短时弛豫机制与介晶旋转是解耦的。此外，我们表明，介晶旋转的粘度对于正确预测软弹性期间的弹性模量不是必需的，但需要正确预测该现象的发生。