A self-consistent interpretation of nuclear magnetic resonance and quasi-elastic neutron scattering data from the smectic A and nematic phases of ethyl 4-(4′ acetoxybenzylidine) aminocinnamate

Abstract

Nuclear magnetic resonance measurements of translational diffusion in the smectic A, nematic and isotropic phases of ethyl 4-(4′ acetoxybenzylidine) aminocinnamate (EABAC) are presented. These and high resolution, incoherent quasi-elastic neutron scattering results are interpreted in terms of anisotropic translational diffusion with a weak (11 kJ mole-1) periodic potential barrier to diffusion perpendicular to the smectic layers. A detailed analysis of the localized diffusive molecular motions in the smectic A and nematic mesophases has confirmed previous indications that there is an appreciable amplitude of motion (∼ 1 Å) parallel to the long molecular axes. This probably results from a coupling with the uniaxial rotational diffusion which the molecules undergo in both mesophases.