Light-scattering study in nematicsmectic-Asmectic-C multicritical mixtures

Light scattering in the bend, splay, and bend-twist modes has been studied in two binary liquid-crystal systems exhibiting the nematicsmectic-Asmectic-C multicritical phase diagram. The results on the behavior of the longitudinal correlation length above the nematicsmectic-A transition are found to be in agreement with x-ray scattering data. The tilt susceptibility above the smectic-Asmectic-C transition is consistent with a simple mean-field description. The pretransitional behavior of the bend and splay elastic constants above the nematicsmectic-C transition in a pure material is found to follow the predictions of the Chen-Lubensky model. Near the multicritical point, the temperature dependence of the light-scattering intensity exhibits an anomalous minimum above the nematicsmectic-C transition in the bend and bend-twist modes but not in the splay mode. This behavior is not described by any existing model.