Mechanical response of smectic-C elastomers.

The elastic response of a smectic-C elastomer to three deformations, namely imposed lambda(xx), lambda(xz), and lambda(zz), has been modeled using a nonlinear theory of a nematic elastomer with embedded smectic layers, and with the director tilt (in the x direction) at a fixed angle with respect to the smectic layer normal (z direction). The main focus is the elastic response after any soft mode of the sample. It is found that the elastomer contracts in the x direction under lambda(xz) shear. On stretching parallel to the layer normal it is found that there is a soft mode that acts to rotate the director toward the z direction. The deformation of the system after this soft mode can be reduced to shear and elongation in the plane of the layers. We make predictions of the mechanical response of the elastomer, in particular the length of the soft plateau and the asymptotic modulus for the elastomer when stretched parallel to the layer normal. Finally, since monodomain Sm-C elastomers are made by the deformation-induced alignment of polydomains, we describe these important systems. Qualitative behavior of the model is then compared to existing experimental literature on the mechanical alignment of polydomains.