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Open AccessArticle

Bifunctional HLD–NAC for Clove Oil Microemulsions

by Jia-Xin Tan and Edgar Acosta

Liquids 2025, 5(3), 23; https://doi.org/10.3390/liquids5030023 - 8 Sep 2025

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Clove oil is an essential oil used in food and pharmaceutical applications, with a market value of 300+ million dollars per year. Microemulsions have been used as effective clove oil delivery vehicles and could also be used to develop new extraction processes from clove buds. Eugenol, the main component of clove oil, is a polar oil that behaves as a surfactant and as an oil. This bifunctional behavior makes formulating clove oil microemulsions a challenging task. Here, we used a version of the Hydrophilic–Lipophilic Difference (HLD) + Net-Average Curvature (NAC) model that incorporates the bifunctional polar oil model to predict and fit the phase behavior of lecithin (surfactant) + polyglycerol-10 caprylate (hydrophilic linker) microemulsions using mixtures of heptane and clove oil as the oil phase. Using HLD-NAC parameters from the literature, the predicted HLD-NAC curves reproduced the expected phase transitions and the trends in Eugenol segregation toward the surfactant layer. Using these literature parameters as an initial guess to fit the experimental phase volumes produced accurate calculated phase volumes, and predicted interfacial tensions. This work demonstrates the application of heuristics and databases of HLD-NAC parameters in predicting the complex phase behavior of surfactant–oil–water (SOW) systems. Full article

(This article belongs to the Collection Feature Papers in Solutions and Liquid Mixtures Research)

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26 pages, 5561 KB

Open AccessArticle

Yeast Viability in HLD–NAC-Designed Fully Dilutable Lecithin-Linker Microemulsions

by Juan Doratt Mendoza, Jingwen Ding, Michelle Acosta Alvarez and Edgar Acosta

Molecules 2025, 30(4), 921; https://doi.org/10.3390/molecules30040921 - 17 Feb 2025

Cited by 1 | Viewed by 1702

Abstract

Using microemulsions (µEs) as preservation media for cells was pursued in the 1990s; however, the difficulty in formulating biocompatible µEs and keeping unacclimatized cells alive for more than three days hindered developments in this area. This work explores the use of fully dilutable self-microemulsifying delivery systems (SMEDS) formulated with lecithin (Le) and polyglycerol-10-caprylate (PG10C) at a ratio of 2/5. This surfactant blend was mixed with ethyl oleate (EOL) at a ratio of 60 surfactant/40 EOL to produce a D60 dilution line. This D60 SMEDS was diluted with 0.9% w/v NaCl solution to produce lecithin-linker µEs (LLMs). The properties of the resulting LLMs were predicted using the hydrophilic–lipophilic-difference (HLD) and net-average curvature (NAC) model, indicating that LLMs with aqueous content from 5% to 60% are bicontinuous, confirmed via viscosity and conductivity. The largest yeast activity and viability obtained with LLMs were achieved with 30% aqueous content, resulting from the balance between having enough water for the effective transport of metabolites, enough SMEDS to contribute nutrients and lipids, and a low enough water to limit the partition of PG10C that, when present in the aqueous phase, inhibited yeast activity. For SMEDS, its low water activity ensured that the yeast remained dormant, keeping them alive for at least 10 weeks. Full article

(This article belongs to the Special Issue Amphiphilic Molecules, Interfaces and Colloids: 2nd Edition)

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19 pages, 6107 KB

Open AccessReview

Microemulsions Based on Diverse Surfactant Molecular Structure: Comparative Analysis and Mechanistic Study

by Jiepeng Qu, Yinhua Wan, Maozhang Tian and Weifeng Lv

Processes 2023, 11(12), 3409; https://doi.org/10.3390/pr11123409 - 12 Dec 2023

Cited by 14 | Viewed by 5414

Abstract

Microemulsion flooding technology, known for significantly reducing interfacial tension, improving rock wettability, and providing strong driving forces at the microscopic level, has been widely applied in enhancing oil recovery in oil fields. This article summarizes the relevant literature and introduces the classification, formation mechanisms, research models, and factors affecting the performance of microemulsions. Particularly, it conducts a comparative analysis of microemulsion systems formed by surfactant molecules of different structures, aiming to provide new perspectives for the study of surfactant molecular structures and to further optimize the performance of microemulsion systems. The study finds that modifying surfactant molecules by adding benzene rings, increasing the length of hydrophobic tails, and enlarging hydrophilic heads can significantly increase the volume of the middle phase, exceeding 30%. These findings provide important guidance for optimizing microemulsion systems. Full article

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40 pages, 4891 KB

Open AccessFeature PaperReview

Microemulsion Microstructure(s): A Tutorial Review

by Giuseppe Tartaro, Helena Mateos, Davide Schirone, Ruggero Angelico and Gerardo Palazzo

Nanomaterials 2020, 10(9), 1657; https://doi.org/10.3390/nano10091657 - 24 Aug 2020

Cited by 193 | Viewed by 18013

Abstract

Microemulsions are thermodynamically stable, transparent, isotropic single-phase mixtures of two immiscible liquids stabilized by surfactants (and possibly other compounds). The assortment of very different microstructures behind such a univocal macroscopic definition is presented together with the experimental approaches to their determination. This tutorial review includes a necessary overview of the microemulsion phase behavior including the effect of temperature and salinity and of the features of living polymerlike micelles and living networks. Once these key learning points have been acquired, the different theoretical models proposed to rationalize the microemulsion microstructures are reviewed. The focus is on the use of these models as a rationale for the formulation of microemulsions with suitable features. Finally, current achievements and challenges of the use of microemulsions are reviewed. Full article

(This article belongs to the Special Issue Micro/Nano Emulsions: Smart Colloids for Multiple Applications)

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