TRANSVERSE DEUTERON SPIN RELAXATION IN THERMOTROPIC LIQUID-CRYSTAL POLYMERS - DETERMINATION OF VISCOELASTIC PROPERTIES

Transverse deuteron spin relaxation times, T2E(CP), from quadrupole echo pulse trains have been measured as a function of pulse spacing, tau, for a thermotropic liquid crystal polymer and dimer in the nematic phase. The relaxation times exhibit a dispersion law, T2E(CP) approximately tau-1/2, consistent with director fluctuations providing the dominant transverse relaxation process. The observed anisotropy in T2E(CP) measured as a function of orientation, theta(N), for the polymer approximately follows the (sin2-theta(N)cos2-theta(N)-1 dependence characteristic of this type of low-amplitude motion. Analysis of the experiments is achieved employing a simple hydrodynamic model for director fluctuations, yielding values for the effective viscosity and average elastic constant of the liquid crystal polymer and dimer.