Polydispersen

Polydispersen is a concept used in discussions of polydisperse systems to describe the state or property of having a broad and structurally varied distribution of components. The term is typically posed as a multidimensional extension of polydispersity, accounting not only for particle size distributions but also for correlated distributions of other properties such as shape, refractive index, surface charge, or chemical composition within a sample.

In theory, polydispersen encompasses the full distribution of a sample's components, often summarized by moments of the distribution beyond the mean and variance, including skewness, kurtosis, and inter-property correlations. It is meant to provide a more complete picture of dispersion than the conventional polydispersity index (PDI), which usually relies on a single metric like Mw/Mn for polymers or a single size parameter for particles.

Measurement and calculation rely on combining data from multiple characterization techniques, such as dynamic light scattering for size, electron microscopy for morphology, SAXS or SANS for shape distributions, and chromatography or field-flow fractionation for compositional spreads. Statistical approaches involve multivariate density estimation, deconvolution, or distribution fitting in multidimensional space.

Applications are discussed in theoretical and applied contexts, including polymer science, colloidal chemistry, and pharmaceuticals, where understanding the full dispersion helps assess stability, rheology, and performance. Limitations include the lack of standard definition, data requirements, and sensitivity to chosen models.