NEUTRON SCATTERING STUDIES OF NEAR SURFACE EFFECTS ON STRUCTURES IN SURFACTANT SYSTEMS. W. A. Hamilton, P. D. Butler, J. B. Hayter, Oak Ridge National Laboratory*, Oak Ridge, TN 37831, USA, L. J. Magid, Z. Han, Department of Chemistry, University of Tennessee - Knoxville, Knoxville, TN 37996-1600, USA

The presence of a solid surface can be expected to modify nearby surfactant structures in solution both statically, due to the constraints imposed by its presence and interactions with any adsorbed layer, and dynamically, by Poiseuille shear in flow past it. Using neutron reflectometry, near-surface small angle neutron scattering (SANS) from reflection geometry cells, and bulk SANS from both static and Couette sheared samples, we have attempted to track the evolution of surface structures into bulk structures over distance from the solid-liquid interface. The most dramatic results of these investigations has been the observation of a system highly extended threadlike micelles under Poiseuille shear flow near a quartz surface ordering into a hexagonal phase. This phase so strongly oriented with respect to the flow direction and the shear gradient that its "crystallites" have mosaic widths of only a few degrees, but Couette shear SANS measurements show that this very highly oriented region may not extend more than a few tens of micron from the surface into the bulk shear field. We also present results of this approach applied to near surface ordering in spherical micellar and multilamellar surfactant systems.

^*managed by Lockheed Martin Energy Research Corporation for the U. S. Department of Energy under contract DE-AC05-960R22464