ROTATIONAL DIFFUSION OF ASYMMETRIC MOLECULES IN LIQUID-CRYSTALS - A GLOBAL ANALYSIS OF DEUTERON RELAXATION DATA

A new global analysis of the relaxation data in the nematic and smecti c A phases of 4-n-pentyloxybenzylidene-4'-heptylaniline [Phys. Rev. E 49, 538 (1994)] supports a model which includes director fluctuations and rotational diffusion of an asymmetric rigid rotor in a biaxial pot ential of mean torque. The molecular biaxiality of the molecule is fou nd, based on the relaxation data, to give a small positive biaxial ord er parameter S-yy-S-xx. In addition, the activation energy for the tum bling motion of the molecule is found to be larger than that for the s pinning motion. The usefulness of globally analyzing the deuteron rela xation data at different temperatures and frequencies is demonstrated. (C) 1996 American Institute of Physics.