Local order and lattice dynamics in the ordered phases of T.B.B.A. (Terephthal-Bis-Butyl-Aniline)

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Abstract
This paper reviews the main results on the structure and the dynamics of the ordered smectic phases of T.B.B.A. The study of lattice dynamics by means of neutron coherent inelastic scattering bears out the X-ray measurements : the smectic Bc and Ec phases show a conventional three-dimensional order, however the molecules may perform motions with large amplitude, this makes the observation of collective modes rather difficult. Moreover we have restarted with neutron techniques the work done with X-rays on the local herring-bone order in the smectic Bc phase of T.B.B.A. Because of the energy analysis, the neutron measurements give better measure of the sizes of different types of domains. It seems that the molecule tilt angle induces only a little anisotropy in a given domain, and thus it is the coupling between smectic layers which favours the growth of a preferential domain near the transition SmBc → SmEc. Moreover a lifetime of the domains has been measured, and appears to be slightly greater than the relaxation time for individual rotational motions of the molecules