Uncovering the nanoscopic phase behavior of ternary solutions in the presence of electrolytes: from pre-Ouzo to Ouzo region

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Main Authors: Li, Mingbo, Lai, Rushi, Tian, Yadi, Gao, Yawen, Wang, Benlong, Sun, Chao
Format: Preprint
Published: 2025
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_version_ 1866918060182470656
author Li, Mingbo
Lai, Rushi
Tian, Yadi
Gao, Yawen
Wang, Benlong
Sun, Chao
author_facet Li, Mingbo
Lai, Rushi
Tian, Yadi
Gao, Yawen
Wang, Benlong
Sun, Chao
contents In this work, we report a comprehensive study of how electrolyte addition governs the structure and stability of surfactant-free microemulsions in a trans-anethol/ethanol/water system. The universal structural response has been validated, spanning the full range of solution dispersed-phase structurings, from sub-10 nm W/O reverse-aggregates to O/W mesoscopic droplets (~100 nm) and classical Ouzo droplets (~1 μm). Experimental results reveal that there is a threshold for electrolyte levels above which oil-in-water nanodroplet coalescence and phase separation are triggered: screening of electrical double layers and "salting out" of hydrophobic components drives hydrotrope into fewer, larger droplets. The total oil volume sequestered in the dispersed phase remains essentially constant, indicating oil redistribution rather than dissolution. In contrast, water-in-oil nanodroplets in a predominantly organic medium display near-complete insensitivity to ionic strength, owing to low dielectric screening and tight interfacial packing that exclude substantial ion uptake. Finally, addition of high salt to Ouzo droplets accelerates their collapse: large droplets fuse and sediment, leaving only residual nanostructures and confirming electrolyte-driven phase demixing. This insight offers clear guidelines for designing additive-free emulsions with tailored lifetimes and nanostructure architectures across pharmaceutical, food, and materials applications.
format Preprint
id arxiv_https___arxiv_org_abs_2506_13377
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Uncovering the nanoscopic phase behavior of ternary solutions in the presence of electrolytes: from pre-Ouzo to Ouzo region
Li, Mingbo
Lai, Rushi
Tian, Yadi
Gao, Yawen
Wang, Benlong
Sun, Chao
Soft Condensed Matter
Chemical Physics
In this work, we report a comprehensive study of how electrolyte addition governs the structure and stability of surfactant-free microemulsions in a trans-anethol/ethanol/water system. The universal structural response has been validated, spanning the full range of solution dispersed-phase structurings, from sub-10 nm W/O reverse-aggregates to O/W mesoscopic droplets (~100 nm) and classical Ouzo droplets (~1 μm). Experimental results reveal that there is a threshold for electrolyte levels above which oil-in-water nanodroplet coalescence and phase separation are triggered: screening of electrical double layers and "salting out" of hydrophobic components drives hydrotrope into fewer, larger droplets. The total oil volume sequestered in the dispersed phase remains essentially constant, indicating oil redistribution rather than dissolution. In contrast, water-in-oil nanodroplets in a predominantly organic medium display near-complete insensitivity to ionic strength, owing to low dielectric screening and tight interfacial packing that exclude substantial ion uptake. Finally, addition of high salt to Ouzo droplets accelerates their collapse: large droplets fuse and sediment, leaving only residual nanostructures and confirming electrolyte-driven phase demixing. This insight offers clear guidelines for designing additive-free emulsions with tailored lifetimes and nanostructure architectures across pharmaceutical, food, and materials applications.
title Uncovering the nanoscopic phase behavior of ternary solutions in the presence of electrolytes: from pre-Ouzo to Ouzo region
topic Soft Condensed Matter
Chemical Physics
url https://arxiv.org/abs/2506.13377