Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125, USA.
Phys Rev E. 2017 Sep;96(3-1):032701. doi: 10.1103/PhysRevE.96.032701. Epub 2017 Sep 18.
Chiral smectic-A liquid crystal elastomers are rubbery materials composed of a lamellar arrangement of liquid crystalline mesogens. It has been shown experimentally that these materials shear when subjected to an electric field due to the electrically induced tilt of the director. Experiments have also shown that shearing a chiral smectic-A elastomer gives rise to a polarization. Roughly, the shear force tilts the directors which, in turn, induce electric dipoles. This paper builds on previous works and models the electromechanical response of smectic-A elastomers using free energy contributions that are associated with the lamellar structure, the relative tilt between the director and the layer normal, and the coupling between the director and the electric field. To illustrate the merit of the proposed model, two cases are considered-a deformation induced polarization and an electrically induced deformation. The predictions according to these two models qualitatively agree with experimental findings. Finally, a cylinder composed of helical smectic layers is also considered. It is shown that the electromechanical response varies as a function of the helix angle.
手性向列相液晶弹性体是由层状排列的液晶介晶组成的橡胶状材料。实验表明，由于介电各向异性的电诱导倾斜，这些材料在受到电场作用时会发生剪切。实验还表明，剪切手性向列相弹性体会产生极化。大致来说，剪切力会倾斜指向器，而指向器又会感应电偶极子。本文在前人的工作基础上，利用与层状结构、指向矢与层法线之间的相对倾斜以及指向矢与电场之间的耦合相关的自由能贡献，对向列相弹性体的机电响应进行建模。为了说明所提出模型的优点，考虑了两种情况——变形诱导极化和电致变形。这两个模型的预测定性上与实验结果一致。最后，还考虑了由螺旋状向列层组成的圆柱体。结果表明，机电响应随螺旋角的变化而变化。
