Ye Fangfu, Lubensky T C
Liquid Crystal Institute, Kent State University, Kent, Ohio 44242-0001, USA.
J Phys Chem B. 2009 Mar 26;113(12):3853-72. doi: 10.1021/jp8082002.
Nematic elastomers with locked-in anisotropy direction exhibit semisoft elastic response characterized by a plateau in the stress-strain curve in which stress does not change with strain. We calculate the global phase diagram for a minimal model, which is equivalent to one describing a nematic in crossed electric and magnetic fields, and show that semisoft behavior is associated with a broken symmetry biaxial phase and that it persists well into the supercritical regime. We also consider generalizations beyond the minimal model, particularly the neo-classical model introduced by Warner, Bladon, and Terentjev, and find similar results. Our work underscores the fact that semisoft response is fundamentally a nonlinear phenomenon and that experiments on samples at zero external stress provide no information about it.
具有锁定各向异性方向的向列型弹性体表现出半软弹性响应，其特征在于应力-应变曲线中的一个平台区，在该区域应力不随应变变化。我们计算了一个最小模型的全局相图，该模型等同于描述在交叉电场和磁场中的向列型的模型，并表明半软行为与一个破缺对称性的双轴相相关，并且它在超临界区域中也能很好地持续存在。我们还考虑了超出最小模型的推广，特别是由华纳、布拉登和特伦捷夫引入的新古典模型，并得到了类似的结果。我们的工作强调了这样一个事实，即半软响应从根本上说是一种非线性现象，并且在零外部应力下对样品进行的实验无法提供有关它的任何信息。
