Further insights into the universality of colloidal aggregation

P Sandkuhler, M Lattuada, H Wu, J Sefcik, M Morbidelli

Research output: Contribution to journalArticle

77 Citations (Scopus)

Abstract

Dynamic light scattering (DLS) performed at various scattering wave vectors provides detailed information about the aggregation kinetics and the cluster mass distribution (CMD) in colloidal dispersions. Detailed modeling of the aggregation kinetics with population balance equations requires a quantitative connection between the CMD and measurable quantities such as the angle dependent hydrodynamic radii obtained by DLS. For this purpose we evaluate and compare various models for the structure factor of fractal aggregates. Additionally, we introduce a simple scattering model that accounts for the contribution of internal cluster dynamics of fractal clusters to the first cumulant of the dynamic structure factor. We show that this contribution allows to quantitatively describe previously measured experimental data [Lin M, Lindsay H, Weitz D, Ball R, Klein R, Meakin P. Universality in colloid aggregation. Nature 1989;339:360.] on the scattering wave vector dependence of the hydrodynamic radius in diffusion limited cluster-cluster aggregation (DLCA), which was shown to exhibit some kind of universality behavior (master curve). Using the same scattering model, we analyze a similar set of experimental data but in reaction limited cluster-cluster aggregation (RLCA). We find that in this case the crossover from RLCA to DLCA and gravitational settling both have a significant influence on the CMD and consequently on the scattering wave vector dependent DLS data. Only when accounting for both these effects they temporarily compensate each other and a satisfactory representation of the aggregation master curve is possible for the RLCA data at longer times. Indeed, we find that either crossover from RLCA to DLCA or gravitational settling, when present individually, causes the loss of a master curve for aggregation.

Original languageEnglish
Pages (from-to)65-83
Number of pages19
JournalAdvances in Colloid and Interface Science
Volume113
Issue number2-3
DOIs
Publication statusPublished - 30 May 2005

Keywords

  • multiangle dynamic light scattering
  • aggregation
  • population balance equations
  • master curves

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