QNS INVESTIGATION OF D-EBBA CORE REORIENTATIONS IN ORIENTED NEMATIC AND ISOTROPIC PHASES

The QNS high resolution measurements of the elastic incoherent structu re factor obtained for the oriented sample of the molecule p-ethoxyben zylidene-p-n-butylphenyl with deuterated tails (d-EBBA) in the nematic and isotropic phases (M. P. Fontana and G. Gallone, 1995, Physica Scr ipta T, 57, 168) have been interpreted successfully, on the basis of t he uniaxial, angular confined, biased reorientational model of the rig id molecular core along its para axis. It was found that the angular s pan of a corresponding circular segments in the nematic phase roughly scales with the nematic order parameter; however, in the isotropic pha se the d-EBBA molecular core uniaxial reorientation is found to be str ongly constrained. The physical origin of the potential barriers, cons training the uniaxial reorientation of the d-EBBA molecular core, is d iscussed.