Small-angle scattering features of lyotropic smectics A

2014 Small-angle neutron scattering experiments on dilute lyotropic smectics A have been performed on oriented samples. The structure factor of a two-component smectic A is derived theoretically, taking explicitly into account the anisotropic coupling between concentration and layer displacement fluctuations. The anisotropic small-angle signal and other characteristic features of the spectra, and their evolutions with dilution, are predicted. The differences between electrostatically and sterically stabilized dilute lamellar phases are emphasized. Experiments are consistently described by the theory. J. Phys. France 51 (1990) 2333-2346 15 OCTOBRE 1990, 1