Improved estimation of the particle size distribution from combined light scattering measurements

Abstract

Light scattering (LS) techniques, such as single-angle dynamic light scattering (DLS), elastic light scattering (ELS), and turbidimetry (T), are frequently used to estimate the particle size distribution (PSD) of a polymeric colloid. Irrespective of the utilized technique, the acquired measurements have low information content on the PSD, and an ill-conditioned numerical inverse problem must be solved. As a consequence, only a low resolution estimate of the PSD can be obtained. However, the PSD resolution can be improved by combining 2 or more sets of independent measurements in a single inverse problem, provided that the latex exhibits an adequate stability to keep invariant its PSD along all the measurements. The improvement of the PSD resolution is due not only to the larger information content on the PSD but also to a better conditioning of the combined inverse problem. Several combined LS techniques are analyzed: multiangle DLS (MDLS), MDLS+ELS, T+ELS, and MDLS+T.