Molecular Packing in Thermotropic Smectic Phases by Neutron and X-Ray Diffraction

X-ray and neutron diffraction measurements of the intensity of the 00/ Bragg reflections from the smectic layers in hydrogenous and partly deuterated isobutyl 4-(4′-phenyl-benzylideneamino)cinnamate are reported. A model calculation has been used to deduce from these intensities, the configuration and orientational order of the molecules. The orientations of the long molecular axes are well ordered with P2 > 0.9 in S E, S B and S A phases and there is no appreciable interdigitation of the molecules of adjacent layers. These results are compared with those obtained from incoherent quasielastic neutron scattering experiments.