Latex particle size distribution by dynamic light scattering: Computer evaluation of two alternative calculation paths

Two calculation paths for estimating the particle size distribution (PSD) o f a polymer latex from single-angle dynamic light scattering (DLS) measurem ents are evaluated on the basis of a numerical example. In the more common "double-step method," two calculation steps are applied, with the intermedi ate estimation of the particle light intensity distribution (PLID). In the "single-step method," the calculation is performed in one operation. From t he specification of several PSDs, a mathematical model is used to produce t he synthetic measurements. An iterative procedure was applied for determini ng the diameter range and the number of PSD points. The inversion operation s were carried out using a regularization technique. For narrow distributio ns with diameters in the range 100-1000 nm, the PSD and the PLID are simila r in shape, and both calculation paths produce similar results. For broad P SDs in the range 100-1000 nm, and for arbitrary PSDs in the range 10-100 nm (i.e., in the Rayleigh region), the single-step method proved preferable. (C) 2000 Academic Press.