  Small-angle neutron scattering (SANS) from cationic globular micellar
solutions composed of sodium dodecyl sulfate (SDS) and in water was studied
with contrast variation approach. Extensive computational studies have
demonstrated that the distribution of invasive water is clearly an important
feature for understanding the self-organization of SDS molecules and the
stability of assemblies. However, in existing scattering studies the degree of
hydration level was not examined explicitly. Here using the scheme of contrast
variation, we establish a methodology of SANS to determine the intra-micellar
radial dis-tributions of invasive water and SDS molecules from the evolving
spectral lineshapes caused by the varying isotopic ratio of water. A detailed
description hydration of SDS micelles is provided, which in an excellent
agreement with known results of many existing simulations studies. Extension of
our method can be used to provide an in-depth insight into the micellization
phenomenon which is commonly found in many soft matter systems.
