DIRECTOR REORIENTATION IN NEMATIC-LIQUID-SINGLE-CRYSTAL ELASTOMERS BYEXTERNAL MECHANICAL-STRESS

As has been shown recently by Kundler and Finkelmann, a sample of nema tic-liquid-single-crystal elastomers subject to a mechanical stress pe rpendicular to the initial director orientation shows a reorientation of the director reminiscent of that observed in low-molecular-weight n ematic Liquid crystals in a magnetic held. Here we present a simple mo del, which captures all the essential features. We calculate the thres hold stress and show that the director reorientation occurs over the e ntire sample. A weakly nonlinear analysis gives a forward bifurcation in agreement with the experimental results. We also discuss the origin of the domain walls in the director observed experimentally and give an expression for the thickness of these walls.