Slow Stress Relaxation in Randomly Disordered Nematic Elastomers and Gels

Randomly disordered liquid crystalline elastomers align under stress. We study the dynamics of stress relaxation before, during, and after the polydomain-monodomain transition. The results for different materials show a universal logarithmic behavior, especially pronounced in the region of the transition. The data are approximated very well by an equation $\ensuremath{\sigma}(t)\ensuremath{-}{\ensuremath{\sigma}}_{\mathrm{eq}}\ensuremath{\sim}1/(1+\ensuremath{\alpha}\mathrm{ln}t)$. We propose a theoretical model based on the cooperative mechanical resistance for the reorientation of each domain, attempting to follow the soft-deformation pathway.