Structure of the hexagonal phase of the sodium dodecyl sulfate and water system

The hexagonal cell parameter a of the system sodium dodecyl sulfate and water in the H_α phase as a function of volume concentration c_ν presents the functional behavior expected for rigid and finite objects: a{∝}c_ν^-1/3. The micellar particle length is, however, unknown since its derivation depends intrinsically on the particle radius R considered. A constant radius is found for the whole H_α domain, and the electron density maps obtained from the x-ray diffracted intensities are analyzed and allow determination of micellar radius (effective radius Reff=18.4±{}0.1 {}, paraffin radius Rₚₐᵣ=16.7±{}0.1 {}, and total radius Rₜₒₜ=20.5±{}1.0 {}). From these values the resulting micellar size is between 170 and 640 {}, with a value of 260 {} for Rₜₒₜ=20.5 {}. {} 1996 The American Physical Society.