Through a mean field theory, an elastic free energy describing the nonuniform elastic textures observed in nematic elastomers, is proposed. To construct it, an order parameter that describes the nematic-isotropic phase transition through the change of the elastic properties of the strain tensor at the transition point is introduced. The resulting elastic free energy can be written in a form that resembles the Frank free energy of the usual nematic liquid crystals, becoming equivalent to it when the size of the elastic nematic domains is a fixed constant along the whole sample. Using this approach, a model for nonhomogeneous deformations found by Godinho et al. [Macromolecules 33, 7675 (2000)] in elastomeric thin films of urethane/urea is proposed.

• Received 13 October 2003

DOI:https://doi.org/10.1103/PhysRevE.69.061704