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Colloids and Interfaces
Special Issues
Emulsion Applications
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Emulsion Applications

A special issue of Colloids and Interfaces (ISSN 2504-5377).

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 25506

Special Issue Editor

Prof. Dr. Spencer Taylor

E-Mail Website
Guest Editor
Centre for Petroleum and Surface Chemistry, Department of Chemistry, University of Surrey, Guildford, Surrey GU2 7XH, UK
Interests: asphaltenes; coalescence and demulsification; crude oils and bitumens—composition and surface properties; emulsions and microemulsions; enhanced oil recovery; industrial colloidal and interfacial systems; surface and interfacial chemistry of petroleum fuels; surfactants; wettability
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Emulsions, whether as products or involved in processes, are all around us in the modern world. The scope of emulsions applications is a result of the skill and imagination of researchers in this field over many years. For decades, the adage that “oil and water do not mix” has been challenged, and with the ready availability of numerous natural and synthetic emulsifiers with molecular characteristics differing in oil/water compatibility, these unlikely bed-fellows are now able to work together in ways that the individual liquids cannot.

This Special Issue is therefore a celebration of emulsion research, embracing both fundamental and applied aspects, which enables the contemporary diversity of emulsions in science and technology to be highlighted.

Of particular interest are contributions in the following categories, relevant to emulsion formulation, characterization, and applications, namely:

  • Developments in complex emulsions (e.g., phase-change, and multiple and Janus emulsions)
  • Oil/water separation—demulsification by physical and chemical means
  • Pickering–Ramsden emulsions
  • Emulsion rheology
  • Emulsion-derived materials and morphology control
  • Highly concentrated emulsions—formulation, properties, and applications
  • Oil-in-oil and water-in-water emulsions
  • Influence of interfacial properties on emulsion characteristics
  • In-situ measurements of emulsion interfacial properties

Contributions are also welcome from the many industries that manufacture or handle emulsions and emulsion products as part of their day-to-day businesses, including food, paint and ink, agrochemical, pharmaceutical, petroleum, and cosmetic industries, to name but a few.

Prof. Dr. Spencer Taylor
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Colloids and Interfaces is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (5 papers)

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Research

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13 pages, 2324 KiB  
Article
Thermal Analysis Tools for Physico-Chemical Characterization and Optimization of Perfluorocarbon Based Emulsions and Bubbles Formulated for Ultrasound Imaging
by Yohann Corvis, Frédéric Rosa, Minh-Tien Tran, Gilles Renault, Nathalie Mignet, Sylvie Crauste-Manciet and Philippe Espeau
Colloids Interfaces 2022, 6(2), 21; https://0-doi-org.brum.beds.ac.uk/10.3390/colloids6020021 - 01 Apr 2022
Cited by 1 | Viewed by 3141
Abstract
Self-emulsifying microbubbles, especially designed to increase the contrast of ultrasound images by the inclusion of perfluorocarbon molecules, have been studied by thermal analysis techniques. The microbubbles were made of a blend of gas (20%), surfactants (50%) and water (30%). The surfactants were mixtures [...] Read more.
Self-emulsifying microbubbles, especially designed to increase the contrast of ultrasound images by the inclusion of perfluorocarbon molecules, have been studied by thermal analysis techniques. The microbubbles were made of a blend of gas (20%), surfactants (50%) and water (30%). The surfactants were mixtures of polysorbate-85, Span-80, poloxamer 188, glycerol and fluorinated surfactant (Zonyl®). Microbubbles have been characterized by means of diffusion light scattering and optical imaging. The effect of Zonyl® on encapsulation rate, as well as gas vaporization temperature and gas release temperature, has been assessed by means of Differential Scanning Calorimetry (DSC) and Thermogravimetric Analyses (TGA). Microscopy and laser granulometry techniques have been also carried out for each formulation in order to determine the number of microbubbles and their size, respectively. Moreover, stability of the emulsions has been evaluated by DSC and confronted with the results obtained from the ultrasound experiments. Average microbubble concentrations of 7.2 × 107 and 8.9 × 107 per mL were obtained for perfluorohexane and perfluoropentane based emulsions, respectively. The present study demonstrates that the amount of encapsulated perfluorocarbon increases and the gas evaporation temperature decreases with the concentration of Zonyl®. Furthermore, the best ultrasound contrast images have been obtained in vitro with the samples containing the lowest Zonyl® concentration. An explication regarding the role of Zonyl® in the emulsion/microbubbles preparations is proposed here in order to optimize self-emulsifying microbubble formulation for pharmaceutical development. Full article
(This article belongs to the Special Issue Emulsion Applications)
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21 pages, 7620 KiB  
Article
An Innovative Miniature Pulsating Emulsification Device: Flow Characterization and Measurement of Emulsion Stability
by Angeliki P. Chondrou, Sotiris P. Evgenidis, Margaritis Kostoglou and Thodoris D. Karapantsios
Colloids Interfaces 2020, 4(1), 7; https://0-doi-org.brum.beds.ac.uk/10.3390/colloids4010007 - 31 Jan 2020
Cited by 3 | Viewed by 2982
Abstract
The aim of this study is the development of an emulsification device for two immiscible liquids with a total volume of approximately 3 mL. The heart of the device is a piston, with an aluminum plate fixed at its tip, which moves periodically [...] Read more.
The aim of this study is the development of an emulsification device for two immiscible liquids with a total volume of approximately 3 mL. The heart of the device is a piston, with an aluminum plate fixed at its tip, which moves periodically up and down inside a rectangular cell. The plate geometry (uniform or non-uniform height) affects significantly both the emulsions stability and the size of the droplets of the prepared emulsions. Five parameters are examined during testing (surfactant type, surfactant concentration, proportion of immiscible liquids, piston stroke frequency, duration of emulsification) and all of them appear to have an important role in the resulting droplet size distribution. A macroscopic theoretical model is developed for the determination of the main hydrodynamic parameters of the innovative device. It is shown that the non-uniform height plate achieves higher shear rates when compared to the uniform height plate because of the smaller gap between the plate and the cell walls. However, the benefits of the higher shear rate are overturned by the larger effective breakage time encountered in the uniform height plate resulting from the larger surface area of its sides. The results of the emulsification experiments are analyzed using the parameter values derived by the developed model. Full article
(This article belongs to the Special Issue Emulsion Applications)
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Graphical abstract

14 pages, 5126 KiB  
Article
Effects of Bentonite Nanoclay and Cetyltrimethyl Ammonium Bromide Modified Bentonite Nanoclay on Phase Inversion of Water-in-Oil Emulsions
by Sileola B. Ogunlaja and Rajinder Pal
Colloids Interfaces 2020, 4(1), 2; https://0-doi-org.brum.beds.ac.uk/10.3390/colloids4010002 - 03 Jan 2020
Cited by 8 | Viewed by 5132
Abstract
The effects of unmodified and modified bentonite nanoclays (with various degrees of surfactant modification) on the catastrophic phase inversion from water-in-oil (W/O) emulsion to oil-in-water (O/W) emulsion were determined experimentally. The bentonite nanoclay (NC-Bt) was suspended in the aqueous phase, and the critical [...] Read more.
The effects of unmodified and modified bentonite nanoclays (with various degrees of surfactant modification) on the catastrophic phase inversion from water-in-oil (W/O) emulsion to oil-in-water (O/W) emulsion were determined experimentally. The bentonite nanoclay (NC-Bt) was suspended in the aqueous phase, and the critical volume fraction of water where phase inversion from W/O to O/W emulsion took place was determined through conductivity measurements. Cetyltrimethyl ammonium bromide (CTAB) was used as a surfactant to modify the nanoclay. The adsorption of CTAB onto nanoclay had a strong influence on the contact angle and the critical volume fraction of water where phase inversion took place. The modification of the nanoclay brought about by the adsorption of CTAB increased the three-phase contact angle (measured through the aqueous phase), thereby making it more hydrophobic, and prolonged the phase inversion point. CTAB alone and CTAB-modified nanoclay delayed the phase inversion process in a similar manner, showing a strong dependence on the CTAB concentration. Full article
(This article belongs to the Special Issue Emulsion Applications)
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13 pages, 2178 KiB  
Article
Oil-In-Water Microemulsions for Thymol Solubilization
by Laura Fernández-Peña, Sonia Gutiérrez-Muro, Eduardo Guzmán, Alejandro Lucia, Francisco Ortega and Ramón G. Rubio
Colloids Interfaces 2019, 3(4), 64; https://0-doi-org.brum.beds.ac.uk/10.3390/colloids3040064 - 02 Dec 2019
Cited by 23 | Viewed by 4010
Abstract
Essential oil compounds (EOCs) are molecules with well-known antimicrobial and antipest activity. However, such molecules possess limited solubility in water, making their handling difficult. This work aimed to enhance the distribution of a solid essential oil compound, thymol, using oil-in-water (o/w) microemulsions for [...] Read more.
Essential oil compounds (EOCs) are molecules with well-known antimicrobial and antipest activity. However, such molecules possess limited solubility in water, making their handling difficult. This work aimed to enhance the distribution of a solid essential oil compound, thymol, using oil-in-water (o/w) microemulsions for its solubilization. The use of mixtures formed by an alkyl polyglucoside (APG) and soybean lecithin (SL) allowed for stabilization of the o/w microemulsions in a broad range of compositions, with the total concentration of the mixture of the two surfactants (APG+SL) and the APG:SL ratio both being essential for controlling the nature of the obtained dispersions. The microemulsions obtained using oleic acid as the oil phase and with compositions far from those corresponding to the onset of the emulsion region showed a good efficiency for thymol solubilization. This is an advantage from a stability point of view, as well as for ease of thymol preparation. The present work opens new alternatives for designing eco-sustainable formulations for EOC solubilization, with the possibility of preparing the formulations at the place of use, thereby saving transport costs and reducing the emission of pollutants. Full article
(This article belongs to the Special Issue Emulsion Applications)
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Review

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18 pages, 4290 KiB  
Review
Evaluating the Stability of Double Emulsions—A Review of the Measurement Techniques for the Systematic Investigation of Instability Mechanisms
by Nico Leister and Heike P. Karbstein
Colloids Interfaces 2020, 4(1), 8; https://0-doi-org.brum.beds.ac.uk/10.3390/colloids4010008 - 31 Jan 2020
Cited by 67 | Viewed by 8704
Abstract
Double emulsions are very promising for various applications in pharmaceutics, cosmetics, and food. Despite lots of published research, only a few products have successfully been marketed due to immense stability problems. This review describes approaches on how to characterize the stability of double [...] Read more.
Double emulsions are very promising for various applications in pharmaceutics, cosmetics, and food. Despite lots of published research, only a few products have successfully been marketed due to immense stability problems. This review describes approaches on how to characterize the stability of double emulsions. The measurement methods are used to investigate the influence of the ingredients or the process on the stability, as well as of the environmental conditions during storage. The described techniques are applied either to double emulsions themselves or to model systems. The presented analysis methods are based on microscopy, rheology, light scattering, marker detection, and differential scanning calorimetry. Many methods for the characterization of double emulsions focus only on the release of the inner water phase or of a marker encapsulated therein. Analysis methods for a specific application rarely give information on the actual mechanism, leading to double emulsion breakage. In contrast, model systems such as simple emulsions, microfluidic emulsions, or single-drop experiments allow for a systematic investigation of diffusion and coalescence between the individual phases. They also give information on the order of magnitude in which they contribute to the failure of the overall system. This review gives an overview of various methods for the characterization of double emulsion stability, describing the underlying assumptions and the information gained. With this review, we intend to assist in the development of stable double emulsion-based products. Full article
(This article belongs to the Special Issue Emulsion Applications)
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