Salt-induced stability and modified interfacial energetics in self-faceting emulsion droplets

Pilkhaz M. Nanikashvili, Alexander V. Butenko, Moshe Deutsch, Daeyeon Lee, Eli Sloutskin

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Hypothesis: The counterintuitive temperature-controlled self-faceting of water-suspended, surfactant-stabilized, liquid oil droplets provides new opportunities in engineering of smart liquids, the properties of which are controllable by external stimuli. However, many emulsions exhibiting self-faceting phenomena have limited stability due to surfactant precipitation. The emulsions’ stability may be enhanced, and their inter-droplet electrostatic repulsion tuned, through controlled charge screening driven by varying-concentration added salts. Moreover, in many technologically-relevant situations, salts may already exist in the emulsion's aqueous phase. Yet, salts’ impact on self-faceting effects has never been explored. We hypothesize that the self-faceting transitions’ temperatures, and stability against surfactant precipitation, of ionic-surfactants-stabilized emulsions are significantly modified by salt introduction. Experiments: We explore the temperature-dependent impact of NaCl and CsCl salt concentration on the emulsions’ phase diagrams, employing optical microscopy of emulsion droplet shapes and interfacial tension measurements, both sensitive to interfacial phase transitions. Findings: A salt concentration dependent increase in the self-faceting transition temperatures is found, and its mechanism elucidated. Our findings allow for a significant enhancement of the emulsions’ stability, and provide the physical understanding necessary for future progress in research and applications of self-faceting phenomena in salt-containing emulsions.

Original languageEnglish
Pages (from-to)131-138
Number of pages8
JournalJournal of Colloid and Interface Science
Volume621
DOIs
StatePublished - Sep 2022

Bibliographical note

Publisher Copyright:
© 2022 Elsevier Inc.

Funding

This research was supported by Grant No. 2110611 from the United States National Science Foundation (NSF) and the United States-Israel Binational Science Foundation (BSF). We acknowledge the Kahn foundation for funding of some of the equipment. We thank J. Ricardo for discussions and technical assistance.

FundersFunder number
National Science Foundation
United States-Israel Binational Science Foundation

    Keywords

    • Emulsion stability
    • Interfacial freezing
    • Polyhedral droplets
    • Salt solution
    • Self-faceting

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