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Surfactants at the Soft Interfacial Layer
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Surfactants at the Soft Interfacial Layer

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Physical Chemistry".

Deadline for manuscript submissions: 31 January 2025 | Viewed by 3939

Special Issue Editor

Dr. Chi Phan

E-Mail Website
Guest Editor
WA School of Mines: Minerals, Energy and Chemical Engineering, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
Interests: chemical engineering; interface science; surfactant; emulsion, foaming, surface charge

Special Issue Information

Dear Colleagues,

Surfactants are a special class of reagents that are found in multiple-phase systems. Although the macro-influence of these molecules is well-reported in many processes, such as flotation, liquid/liquid solvent extraction, emulsification, de-emulsification and foaming, the fundamental properties at the interface remain unclear. The classical concept of surface excess reveals little information about the interfacial layer. Recent progress in the field has indirectly provided new research directions and insights. Advances in organic synthesis enable precise molecular structure control and thus provide a structure–properties relationship. On the other hand, molecular simulations provide detailed insights into the interactions/arrangement/bonding dynamics of the surfactant-laden interfacial layer. Advanced experimental techniques enable accurate measurements for surfactant-controlled processes, such as dynamic adsorption, drainage of the foaming, diffusiophoresis and spontaneous emulsification. This Special Issue highlights selected applications and discusses key opportunities that can help optimize surfactants’ application. We aim to focus on the selection of reviews and original research reporting on the interfacial phenomena. Additionally, research showing advanced technologies related to formulations of surfactants, solvents and ions is also a focus of this Special Issue. We also welcome authors who can contribute original research on surfactants' mechanisms of action at the interface.

Dr. Chi Phan
Guest Editor

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Keywords

  • surfactant
  • water surface
  • evaporation
  • emulsion
  • foaming

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Published Papers (4 papers)

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Research

12 pages, 1666 KiB  
Article
Distinct Solubilization Mechanisms of Medroxyprogesterone in Gemini Surfactant Micelles: A Comparative Study with Progesterone
by Hiromichi Nakahara, Kazutaka Koga and Keisuke Matsuoka
Molecules 2024, 29(20), 4945; https://doi.org/10.3390/molecules29204945 - 19 Oct 2024
Viewed by 645
Abstract
The solubilization behavior of medroxyprogesterone (MP) within gemini surfactant micelles (14-6-14,2Br−) was investigated and compared with that of progesterone to uncover distinct solubilization mechanisms. We employed 1H-NMR and 2D ROESY spectroscopy to elucidate the spatial positioning of MP within the [...] Read more.
The solubilization behavior of medroxyprogesterone (MP) within gemini surfactant micelles (14-6-14,2Br−) was investigated and compared with that of progesterone to uncover distinct solubilization mechanisms. We employed 1H-NMR and 2D ROESY spectroscopy to elucidate the spatial positioning of MP within the micelle, revealing that MP integrates more deeply into the micellar core. This behavior is linked to the unique structural features of MP, particularly its 17β-acetyl group, which promotes enhanced interactions with the hydrophobic regions of the micelle, while the 6α-methyl group interacts with the hydrophilic regions of the micelle. The 2D ROESY correlations specifically highlighted interactions between the hydrophobic chains of the surfactant and two protons of MP, H22 and H19. Complementary machine learning and electron density analyses supported these spectroscopic findings, underscoring the pivotal role of the molecular characteristics of MP in its solubilization behavior. These insights into the solubilization dynamics of MP not only advance our understanding of hydrophobic compound incorporation in gemini surfactant micelles but also indicate the potential of 14-6-14,2Br− micelles for diverse drug delivery applications. Full article
(This article belongs to the Special Issue Surfactants at the Soft Interfacial Layer)
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19 pages, 10942 KiB  
Article
Adsorption and Aggregation Behaviors of Oleyl Alcohol-Based Extended Surfactant and Its Mixtures
by Ping Li, Peiyu Ren, Shuoyu Wang, Jiangshan Wang, Zidan Sun, Jiayi Sun and Weibo Gu
Molecules 2024, 29(11), 2570; https://doi.org/10.3390/molecules29112570 - 30 May 2024
Cited by 1 | Viewed by 681
Abstract
An oleyl alcohol-based extended surfactant, sodium oleyl polyethylene oxide-polypropylene oxide sulfate (OE3P3S), was synthesized and identified using FT-IR and 1H NMR. The adsorption and aggregation behaviors of OE3P3S and its mixture with cationic surfactant [...] Read more.
An oleyl alcohol-based extended surfactant, sodium oleyl polyethylene oxide-polypropylene oxide sulfate (OE3P3S), was synthesized and identified using FT-IR and 1H NMR. The adsorption and aggregation behaviors of OE3P3S and its mixture with cationic surfactant alkyltrimethylammoniumbromide (ATAB) were investigated under different molar ratios. The static surface tension analysis indicated that the critical micellization concentration (cmc) and the critical surface tension (γcmc) of OE3P3S were 0.72 mmol/L, and 36.16 mN/m, respectively. The cmc and γcmc values of the binary system were much lower than that of the individual component. And the cmc values of OE3P3S/ATAB = 6:4 mixtures decreased with an increase in the chain length of the cationic surfactant in the binary system. It was found from the dynamic surface tension that there was a slower diffusion rate in the binary system compared to the pure surfactant, and the adsorption processes for OE3P3S/ATAB = 6:4 were mixed diffusion-kinetic adsorption mechanisms. With a combination of DLS data and TEM measurements, formations of vesicles in OE3P3S/ATAB = 6:4 solutions appeared to occur at a concentration of 0.05 mmol/L. By studying the formation of liquid crystal structures in an emulsion prepared with OE3P3S as the surfactant, it was found that the oil-in-water emulsion is birefringent with a Maltese cross texture, and the rheological properties revealed its predominant viscoelastic behavior and shear thinning properties. Full article
(This article belongs to the Special Issue Surfactants at the Soft Interfacial Layer)
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14 pages, 4801 KiB  
Article
The Response Surface Methodology for Assessment of HLB Values of Mixtures of Non-Ionic Surfactants Using Parameters from Their π-A Isotherms
by Remigiusz Zapolski and Witold Musiał
Molecules 2024, 29(10), 2351; https://doi.org/10.3390/molecules29102351 - 16 May 2024
Viewed by 1036
Abstract
The aim of the work was to determine important parameters of the course of π-A isotherms, which can determine the HLB (hydrophilic-lipophilic balance) value of surfactant mixtures with selected structural features, such as a straight or branched hydrocarbon chain and a double bond, [...] Read more.
The aim of the work was to determine important parameters of the course of π-A isotherms, which can determine the HLB (hydrophilic-lipophilic balance) value of surfactant mixtures with selected structural features, such as a straight or branched hydrocarbon chain and a double bond, using RSM (response surface methodology) computational methods. Mixtures of surfactants derived from fatty acids and sorbitan with specific HLB values were evaluated by Langmuir trough. The resulting elasticity modules (ELM) and molecules surfaces (SAM) were evaluated via response surface methodology and respective equations were calculated. The π-A isotherm determined in a Langmuir trough and the ELM and SAM parameters determined on the basis of this isotherm may be useful for determining the HLB of a fixed surfactant mixture. The RSM method used, in which ELM and SAM were assumed as two independent variables, can be a useful technique for tracking the influence of individual molecular characteristics on the hydrophilic-lipophilic properties of mixtures of surfactant compounds. Changes in HLB as a dependent variable can be described as a function of ELM and SAM. Full article
(This article belongs to the Special Issue Surfactants at the Soft Interfacial Layer)
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13 pages, 7229 KiB  
Article
Coagulation of Hydrophobic Ionic Associates of Cetyltrimethylammonium Bromide and Carrageenan
by Alexander Shyichuk, Dorota Ziółkowska and Joanna Szulc
Molecules 2023, 28(22), 7584; https://doi.org/10.3390/molecules28227584 - 14 Nov 2023
Cited by 2 | Viewed by 1082
Abstract
In aqueous solutions, cetyltrimethylammonium cations bind to carrageenan polyanions, and the resulting ionic associates form macroscopic aggregates due to hydrophobic interaction. At certain ratios of cetyltrimethylammonium to carrageenan, the resulting colloidal particles auto-flocculate. According to visual observations, the ratio ranges from 1 to [...] Read more.
In aqueous solutions, cetyltrimethylammonium cations bind to carrageenan polyanions, and the resulting ionic associates form macroscopic aggregates due to hydrophobic interaction. At certain ratios of cetyltrimethylammonium to carrageenan, the resulting colloidal particles auto-flocculate. According to visual observations, the ratio ranges from 1 to 3 mmol/g; otherwise the suspensions are stable. By measuring the sedimentation rate and particle size distribution, the most extensive flocculation was found to be from 1.7 to 2.3 mmol/g. The ratio corresponding to the fastest auto-flocculation was precisely determined by titrating the reagents with small increments and recording the turbidity. The turbidimetric titration plots contain distinct break points corresponding to the most extensive flocculation. These break points occur at the same ratio of carrageenan to cetyltrimethylammonium over a wide range of reagent concentrations. The precise values of the critical ratio were found to be 1.78 and 1.53 mmol/g, respectively, during the titration of cetyltrimethylammonium with carrageenan and vice versa. The number of anionic sulfate groups in carrageenan was measured by ICP OES and found to be 1.35 mmol/g. This value is consistent with the critical ratio of the auto-flocculation. Full article
(This article belongs to the Special Issue Surfactants at the Soft Interfacial Layer)
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