Particle Size Distribution of Multimodal Polymer Dispersions by Multiangle Dynamic Light Scattering. Solution of the Inverse Problem on the Basis of a Genetic Algorithm

Abstract

Abstract A method for estimating the particle size distribution (PSD) of dilute latexes from multiangle dynamic light scattering (MDLS) measurements is presented. The estimation procedure includes two main steps: 1) the calculation of the angle‐dependent average diameters of the PSD from MDLS measurements, and 2) the estimation of the PSD through an optimization strategy based on a genetic algorithm (GA). First, the capability of the method was tested on the basis of three simulated examples that involved different PSD shapes, widths, and diameter ranges. Then, the method was employed for estimating the PSD of three samples: a polystyrene latex standard of narrow PSD and known nominal diameter; a mixture of two polystyrene standards of narrow PSDs; and an industrial latex of unknown composition. For comparison, all examples were also solved by numerical inversion of the MDLS autocorrelation measurements through a linear constrained Tikhonov regularization technique. The proposed method appears as an effective and robust tool for characterizing unimodal and multimodal PSDs, without requiring any a priori assumption on the mode shapes or on the PSD diameter range.