X-ray Scattering Studies of Aligned, Stacked Surfactant Membranes

X-ray scattering studies were performed to understand the structure and correlations in the lamellar phases of thick, freely suspended films of (i) the hydrated phospholipid dimyristoylphosphotidylcholine (DMPC) and (ii) the ternary system consisting of the surfactant sodium dodecyl sulfate (SDS), consurfactant (pentanol), and water. The films were drawn in a temperature- and humidity-controlled environment, where the layers were oriented to within 0.1°. In the DMPC system, this made it possible to directly observe the orientation of the P$_{\beta ^{\prime}}$ modulation and to identify phase L$_{\beta ^{\prime}}$ as three distinct phases distinguished by the direction of chain tilt with respect to the lattice. In the L$_{\alpha}$ phase of the ternary system, power law behavior of the (0,0,L) structure factor arising from the algebraic decay of layer correlations was observed in single crystals.