Scientific article
OA Policy
English

Measuring slow heteroaggregation rates in the presence of fast homoaggregation

Published inJournal of Colloid and Interface Science, vol. 566, p. 143-152
Publication date2020
Abstract

Homoaggregation and heteroaggregation involving amidine and sulfate latex particles in the presence of the anionic surfactant octyl sulfate (OS) is studied by light scattering. This surfactant causes a charge reversal of the amidine particles. This reversal induces a rapid homoaggregation near the charge reversal point. In the presence of the same surfactant, the sulfate particles remain negatively charged and stable. The heteroaggregation process is probed in mixed suspensions of amidine and sulfate latex particles with multi-angle time-resolved dynamic light scattering. This technique allows differentiating between the contributions of homoaggregation and heteroaggregation, and permits to measure the heteroaggregation rate. By optimally choosing the sizes of the particles, one can optimize the contrast and extract heteroaggregation stability ratio over a wide range. The heteroaggregation rate is fast at low OS concentrations, where the two particles are oppositely charged. This rate slows down at higher OS concentrations due to double layer repulsion between the negatively charged particles. However, the onset of this slow heteroaggregation occurs at lower OS concentrations than for homoaggregation. The reason for this shift is that the double layer repulsion between two OS-decorated amidine particles is weaker than between one sulfate particle and one OS-decorated amidine particle. These measurements compare favorably with calculations with the theory by Derjaguin, Landau, Verwey, and Overbeek (DLVO). These calculations suggest that constant potential boundary conditions are more appropriate than the ones of constant charge. In the system studied, the present light scattering technique permits to extract heteroaggregation

Keywords
  • Heterocoagulation
  • Latex particles
  • Colloidal stability
  • Electrophoresis
  • DLVO theory
Research groups
Citation (ISO format)
CAO, Tianchi, TREFALT, Gregor, BORKOVEC, Michal. Measuring slow heteroaggregation rates in the presence of fast homoaggregation. In: Journal of Colloid and Interface Science, 2020, vol. 566, p. 143–152. doi: 10.1016/j.jcis.2020.01.075
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Article (Accepted version)
accessLevelPublic
Identifiers
Journal ISSN0021-9797
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Creation03/04/2020 09:43:00
First validation03/04/2020 09:43:00
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