``Soft elasticity'' — deformation without resistance in liquid crystal elastomers

Polymeric nematic liquid crystals crosslinked into elastomers (solid liquid crystals) are shown to display novel and complex elasticity. The internal (nematic) direction can experience a barrier to its rotation which couples to standard elasticity. We predict a new phenomena unique to anisotropic rubber a “soft elastic response”; uniaxial strain is developed without resistance below a critical deformation λ^{star} due to the relaxation of related shear strains and reorientation of the nematic director. We discuss possible experiments to verify this prediction and interpret the existing experimental observation in terms of the concept of “soft elasticity”.