INFLUENCE OF THE CHEMICAL NATURE OF VARIOUS GEOMETRIES ON THE RHEOLOGICAL BEHAVIOR OF A LAMELLAR LYOTROPIC PHASE

The influence of the chemical nature of the substrate was studied in order to determine its impact on the rheological behavior of lyotropic lamellar phases. Small-angle x-ray diffraction analysis established that the plastic behavior of the samples could be explained by the large disorganization of the lamellar layers in the vicinity of surfaces as stainless steel, gold, tin, copper, and bismuth. On the other hand, layer alignment was almost perfect on quartz, and the lamellar samples displayed a dominant viscous behavior induced by the flow of the lamellar layers in the vicinity of the surfaces. On zinc sulfide, an in between behavior was observed and the lamellar sample showed two yield stress: one is necessary to induce local alignment of layers in the vicinity of the surfaces, and the other must align the layers of the lamellar sandwich in the flow direction. Assumptions as to the origin of the complex and varied organization have been studied by considering the surface free energy and the surface top...