Ultrasonic measurements of the anisotropic viscoelastic properties of a nematic elastomer

Abstract
The magnitude and angular dependence of the velocity and the damping for the propagation of a longitudinal ultrasonic wave in the nematic phase of a liquid-crystalline elastomer have been determined. The system exhibits a strong anisotropy of the elastic and viscous coefficients comparable to the behavior found in noncross-linked liquid-crystalline polymers. The data suggest a coupling of the density change to a reorientational motion of the mesogenic side chain which takes place on a 109107 s timescale.