A nonlinear theory accounting for stress-induced orientational transitions in nematic gels

Stress-induced orientational transitions have been observed during the mechanical extension of nematic gels or elastomers with the director of liquid crystalline polymers initially aligned perpendicular to the axis of extension. In contrast to a large body of proposed models for nematic elastomers, few studies exist to interpret such phenomena in nematic gels. Based on free energy minimization, this paper constructs a nonlinear continuum theory to simulate the stress-induced orientational transition in a stretched sheet of nematic gel. The theory shows that the director of liquid crystalline polymers rotates abruptly from its initial alignment to the direction parallel to the axis of extension when the magnitude of the applied stress reaches a critical value.