Abstract
An aligned sample in the lamellar phase of the sodium dodecylsulphate–decanol–water system is investigated by orientation-dependent NMR spin-relaxation experiments and x-ray diffraction. A pronounced relaxation anisotropy is observed, implying a nonclassical microstructure where a large fraction of the hydrocarbon-water interface is highly curved. Noting that the bilayer topology is either oil-continuous, bicontinuous, or water-continuous, we consider three classes of microstructures with curvature defects: a bilayer perforated by aqueous pores, a bilayer with aqueous slits and ribbonlike aggregates, and a bilayer fragmented into discrete discoidal micelles. The seven model-independent NMR observables impose severe constraints on the allowed microstructures: the discoid geometry can be rejected, while the pore and ribbon geometries are consistent with the data, but only for certain values of the relative defect dimensions. A simple analysis of the energetics of defect formation, using the deduced defect dimensions, favors the ribbon geometry.
- Received 7 December 1992
DOI:https://doi.org/10.1103/PhysRevE.47.3374
©1993 American Physical Society