Utilising spatial frequency filtering to extract nanoscale layer structure information from isotropic small-angle X-ray scattering data

 A separation method by spatial frequency filtering of the diffuse background of small-angle X-ray scattering (SAXS) is transferred to the case of isotropically scattering samples of polymer materials. Analysis of the residual discrete SAXS is demonstrated. Evaluations of model scattering curves from lamellar two-phase systems show that this technique, in general, results in a good separation. If samples with pure particle scattering or such with rough domain surfaces are investigated, the separation of a suitable background is possible, but is prone to some uncertainty which is estimated. In the case of particle scattering from lamellae the problem is solved by fitting a model function considering polydispersity to the Lorentz-corrected scattering intensity. After background correction the residual information on the distorted nanostructure is collected in an interface distribution function, from which topological parameters can be recovered with high accuracy. These parameters comprise average layer thicknesses and parameters of particle polydispersity. Parameter recovery is achieved by nonlinear regression with model functions describing stacking statistics. Automated versions of the technique are suited to process and analyse series of polymers collected in time-resolved synchrotron radiation experiments. Received: 24 July 2001 Accepted: 12 September 2001