Semidilute solutions from SAXS

Figure 3.9 presents experimental results obtained from small angle X-ray scattering (SAXS) experiments on semidilute solutions of polystyrene in toluene, choosing three different concentrations. They agree with Eq. (3.62) and enable a determination of the concentration dependence of to be made. 

SANS measurements of polymers in dilute solution (i.e. below the overlap concentration, at which molecules start to interpenetrate) offer basically the same information as that from LS light and X-ray-scattering techniques, which permit the elucidation of chain dimensions via the electron-density contrast between a macromolecule and solvent. A greater signal-to-noise ratio may be obtained with the neutron technique since it is less sensitive to dust particles [44] and also because of the larger contrast possible with a deuterated polymer (or solvent). However, the main impact of SANS has been in the area of semidilute and concentrated systems. The technique has provided a wealth of new information previously unobtainable by LS or SAXS, for which intermolecular interference effects had restricted... 

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