Selection of single scattering from multiple scattering systems by 3D cross-correlation. 2. Concentrated polymer solutions

The effect of multiple scattering from macromolecules was studied on the example of branched amylopectin molecules (waxy maize starch) in water by application of the 3D cross-correlation technique. When the results are compared with those from latex particles of the same hydrodynamic radius, a much weaker influence of multiple scattering on the angular dependence of the static light scattering intensities from amylopectin was observed. Monte Carlo simulations confirmed that this effect can be explained by the weaker decay of the particle scattering factor of the macromolecules compared with hard spheres. Furthermore, we observed no noticeable influence of multiple scattering on the time correlation function (TCF) in dynamic light scattering. We give an attempt of an explanation that is supported by Monte Carlo simulations. Accordingly, the influence decreases with increasing size of the particles or macromolecules. The TCFs of amylopectin were measured at 1% (w/w), 8.7% (w/w), and 20% (w/w). A strong reduction of the segmental mobility was observed as the concentration was increased, and finally hard-sphere behavior was obtained. The observations are in agreement with earlier experimental findings carried out with degraded amylopectins.