Mechanical response of smectic C elastomers

Cambridge University

The elastic response of a smectic C elastomer to the three deformations of imposed $\l{xx}$, $\l{xz}$ and $\l{zz}$ is modelled using a non-linear theory of a nematic elastomer with embedded smectic layers, and a rigid tilt of the director with respect to the smectic layer normal. The main focus is the elastic response after any soft mode of the sample. It is found that the elastomer contracts in the $\vec{x}$ direction under $\l{xz}$ shear. On stretching parallel to the layer normal it is found that there is a soft mode that acts to rotate the director towards the $\vec{z}$ direction. The deformation of the system after this soft mode can be reduced to shear perpendicular to the layers and an elongation parallel to the layers. Experimentally testable 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. The model is then qualitatively compared to existing experimental literature on the mechanical alignment of polydomains.

Full Document