Fried Eliot, Sellers Shaun
Department of Mechanical and Aerospace Engineering, Washington University in St. Louis, 1 Brookings Drive, Box 1185, St. Louis, Missouri 63130-4899, USA.
J Chem Phys. 2005 Jul 22;123(4):044901. doi: 10.1063/1.1979479.
Nematic elastomers exhibit large, spontaneous shape changes at the transition from the high-temperature isotropic phase to the low-temperature nematic phase. These finite deformations are studied here in the context of a nonlinear, properly invariant, variational theory that couples the orientational order and elastic deformation. The theory is based on the minimization of a free-energy functional that consists of two contributions: a nematic one due to the interaction of the mesogenic units and an elastic one arising from the stretching of the cross-linked polymer chains. Suitable choices for these two contributions allow for large, reversible, spontaneous shape changes in which the elastic deformation can affect the isotropic-nematic transition temperature. The change in transition temperature as well as the magnitude of the resulting spontaneous deformation is illustrated for various parameter values. The theory includes soft elasticity as a special case but is not restricted to it.
向列型弹性体在从高温各向同性相转变为低温向列相时会呈现出大幅度的自发形状变化。本文在一个耦合取向有序和弹性变形的非线性、恰当不变的变分理论框架下研究这些有限变形。该理论基于一个自由能泛函的最小化，这个自由能泛函由两部分组成：一部分是由于介晶单元相互作用产生的向列项，另一部分是由交联聚合物链的拉伸引起的弹性项。对这两部分做出合适的选择可以实现大幅度、可逆的自发形状变化，其中弹性变形会影响各向同性 - 向列相转变温度。针对各种参数值展示了转变温度的变化以及由此产生的自发变形的幅度。该理论将软弹性作为一种特殊情况包含在内，但并不局限于此。
