Light, X-Ray, and Neutron Scattering

Scattering methods are among the most powerful and widely used in the study of complex fluids. Light, x-rays, and neutrons can be scattered (Lindner and Zemb 1991). For light scattering, length scales of 2000 A to 100 p,m are probed, while both x-rays and neutrons can reach smaller length scales, from 10 to 1000 A for x rays and from 10 to 200 A for neutrons. 

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In addition to light, x-ray and neutron scattering can be used to obtain size distribution information [79,80]. The latter two techniques can provide information on smaller dispersed species sizes, down to about 0.5 nm. 

While rheological measurements are wonderfully quantitative, they are usually poor qualitative probes of fluid structure. This is because in rheological experiments, the structural changes responsible for the measured relaxation behavior remain hidden. Thus, rheometry is often most useful when supplemented by other experimental methods that characterize fluid structure and flow-induced structural changes. Some of the most useful methods are microscopy, light, x-ray, and neutron scattering, and polarimetry. 

Scattering techniques, such as light, x-ray, and neutron scattering, are extensively used to investigate various structural features of polymeric systems, including crystalline order and crystallinity, conformation, local structure, domain sizes, etc. 

Scattering Techniques. The thickness of adsorbed layers can be determined using light. X-ray, and neutron scattering techniques (3). Quasi-elastic light scattering measurements on dispersion of particles measure the diffusion coefficients of particles in the dispersion. The size of these particles is related to the diffusion coefficient by the Stokes-Einstein equation. This measurement is performed on the dispersion with and without the adsorbed polymer. The difference in the radii in the two measurements is the thickness of the adsorbed layer. In these measurements it should be ensured that the particles in the dispersion are monodisperse and that there is no flocculation. In X-ray and neutron... 

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