Rheological behaviour of attractive emulsions differing in droplet-droplet interaction strength

Philipp L. Fuhrmann, Swantje Breunig, Guido Sala, Leonard Sagis, Markus Stieger, Elke Scholten*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Hypothesis: We hypothesise that interaction strength between oil droplets determine the rheological properties of oil-in-water (O/W) emulsions by simultaneous formation and break-up of bonds between droplets. Using small (SAOS) and large (LAOS) amplitude oscillatory shear measurements, we aim to distinguish different classes of emulsions based on the specific microstructural evolution of the emulsions. Experiments: Concentrated O/W emulsions differing in droplet-droplet interaction strength were obtained. Different interaction strength was obtained using different types of interactions; (a) electrostatic attraction, (b) salt bridging, or (c) crosslinking. Findings: In line with our hypothesis, different rheological events in emulsions depend on the droplet-droplet interaction strength. Strong interactions lead to monotonous yielding, and droplets undergo jamming or densification to provide strain hardening and gel-like behaviour. Emulsions with weak interactions exhibit two-step yielding (SAOS) and continuous yielding in LAOS; indicating a soft-glassy material. In emulsions above maximum packing, and with weak interactions the rheology is controlled by cluster/cage breaking, and transient formation of new clusters. For medium-strength interactions, two-step yielding was reduced, and apparent stain-hardening occurred. The probability of two distinct time scales of yielding is hindered by stronger interactions and jamming. Overall, in concentrated emulsions, yielding is determined by network rupture and reformation, cluster rearrangement and -breaking, which in turn is influenced by interaction type and strength. We present a more differentiated categorisation of emulsions based on interaction strength.

Original languageEnglish
Pages (from-to)389-400
Number of pages12
JournalJournal of Colloid and Interface Science
Volume607
DOIs
Publication statusPublished - Feb 2022

Keywords

  • Clustering
  • Droplet-droplet interaction
  • Emulsion
  • LAOS
  • Polyphenol
  • Rheology
  • Yielding

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