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Measuring slow heteroaggregation rates in the presence of fast homoaggregation

Publié dansJournal of Colloid and Interface Science, vol. 566, p. 143-152
Date de publication2020
Résumé

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

Mots-clés
  • Heterocoagulation
  • Latex particles
  • Colloidal stability
  • Electrophoresis
  • DLVO theory
Groupe de recherche
Citation (format ISO)
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
Fichiers principaux (1)
Article (Accepted version)
accessLevelPublic
Identifiants
ISSN du journal0021-9797
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Informations techniques

Création03/04/2020 09:43:00
Première validation03/04/2020 09:43:00
Heure de mise à jour15/03/2023 21:27:51
Changement de statut15/03/2023 21:27:50
Dernière indexation17/01/2024 09:33:23
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