Small and wide angle X-ray scattering ( SAXS/WAXS )

Small and wide-angle X-ray scattering is a useful and complementary method for determining the size, size distribution and structure of a wide range of disordered (non-crystalline or semi-crystalline) materials. Examples include polymers, liquid crystals, oils, suspensions and biological samples like fibres or protein molecules in solution. The chemical and physical behaviour of these materials is influenced by the structural properties on a typical length scale of 0.1-200 nm. Small-angle X-ray scattering (SAXS) covers the range 2-200 nm and occurs at low scattering angles (1-10°) whilst wide-angle X-ray scattering (WAXS) routinely covers the angular range 7-60°. The technique is used beneficially when applied simultaneously with methods that influence and/or change the samples' structural characteristics (e.g. during temperature changes, under shear forces or upon the application of electric/magnetic field stimuli). The high flux of synchrotron X-rays allows us to follow these changes in a time-resolved manner.

The high intensity of X-rays produced from synchrotron radiation sources enables dynamic X-ray scattering experiments to be performed on materials contained within sample environments that mimic processing conditions and mechanical function. For example in polymers it can provide information on crystallite size, unit cell size, thickness of the interface between microphases, or between the crystalline and amorphous regions. For proteins in solution it provides information regarding size in terms of the radius of gyration, insights into the distance distribution function of the sample (its maximum size envelope), shape and an a priori shape reconstruction or a low resolution, model-independent molecular envelope structure.

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