Global Analysis of Dynamic Light Scattering Autocorrelation Functions

Dynamic light scattering has become a standard technique of investigating colloidal suspensions and polymer solutions. The experimental field autocorrelation function ĝ 1 (t) can often be well modelled by a Laplace transform relating ĝ 1 (t) to a distribution of decay times A(τ). In simple systems A(τ) can usually be directly related to a distribution of molecular weights, particle sizes, diffusion coefficients or other physically relevant quantities, With constrained regularization methods, the parameter‐free estimation of A(τ) has become straightforward. In complex systems, the resulting A(τ) may contain several components the identification of which is not always obvious. The problem often originates in a superposition of diffusive and angle‐independent components that have different variations of their respective decay times with the scattering vector. A method is presented based on a simultaneous fit of several autocorrelation functions measured at several different scattering angles, which, using simple and reasonable assumptions, yields a robust analysis of the spectra of decay times. The application of the method is illustrated on simulated autocorrelation functions and also on real experimental data obtained on a variety of different polymer systems.