Volume 62, Issue 2

The modern surfactant industry demands more efficient and environmentally friendly products as environmental regulations become more stringent. Amino acid Gemini surfactants (AAGSs), as the emerging green surfactants of amino acid surfactants, together with the Geminis, which consist of two or more amphiphilic moieties chemically linked by a spacer group, are the most reliable of these efficient green chemicals. With the diversity of structure and topological configuration of the spacer group, AAGSs have stronger aggregation ability and multifarious molecular configuration and aggregation morphology. They are used in various fields such as pharmaceuticals, biomedicine, daily chemicals, oil recovery and environmental treatment. This review contains detailed discussions on the synthesis of AAGSs from natural and non-natural sources using reactions such as Hofmann alkylation and Schotten-Baumann condensation. The physicochemical properties such as low CMC, good emulsification, different micelle forms, high biodegradability, antibacterial ability and biocompatibility are presented. Future research directions of AAGSs are also suggested, including their optimized synthesis, clarification of structure-performance relationships, and exploration of new applications in a wider range of fields.

A group of cationic Gemini surfactants with ester spacers, C 12 -E 2 -C 12 , C 16 -E 2 -C 16 , C 18 -E 2 -C 18 , were synthesized and confirmed by IR, 1 H NMR and MS. The surface parameters of the synthesized Gemini surfactants including: the critical micelle concentration ( CMC ), the surface tension value at CMC ( γ CMC ), efficiency (p C 20 ), maximum surface excess ( Γ max ) and minimum surface area ( A min ), were obtained from surface tension measurements. These Gemini surfactants showed higher surface activity than the traditional monomeric surfactants. The thermodynamic parameters of the micellization process from conductivity measurements showed that the micellization was a spontaneous and exothermic process, and the micellization process became less favorable with decreasing alkyl chain length and increasing temperature. The micro polarity was evaluated from steady-state fluorescence spectra. It was found that the micelle aggregation number of C n -E 2 -C n aqueous solution gradually increased with the increase of alkyl chain.

The branching of the hydrophobic tail has a significant impact on the performance of branched-chain surfactants, while the influence of hydrophilic headgroups on the surface properties of branched-chain anionic surfactants is rarely reported. In this work, three branched-chain anionic surfactants with the same carbon number and hydrophobic tail architecture but different hydrophilic groups, C 8 sodium branched-chain alkylsulfonate (C 8 SBCAS), C 8 sodium branched-chain alkylphosphonate (C 8 SBCAP), C 8 sodium Guerbet alcohol sulfate (C 8 SGAS) with sulfonate, phosphonate and sulfate groups, respectively, were synthesized. Their surfactant properties, including equilibrium surface tension, dynamic surface tension, wetting ability and foaming property, were thoroughly investigated. The order of the critical micelle concentration ( CMC ) is C 8 SGAS < C 8 SBCAP < C 8 SBCAS, and the equilibrium surface tension ( γ CMC ) follows the order C 8 SBCAP < C 8 SBCAS < C 8 SGAS. These results indicated that increasing the polarity of the hydrophilic headgroups and weakening the charge effect could reduce the hydrophobicity of surfactants, thereby improving their wetting ability and foaming properties. This study provides new insights into the influence of hydrophilic headgroups on the properties of branched-chain anionic surfactants to meet the specific needs of different sectors.

This study investigates the effects of 10 % v/v dimethyl sulfoxide (DMSO), acetonitrile (ACN), and 1-propanol (1-PrOH) on the micellar and surface behavior of three ionic surfactants: sodiumdodecyl sulfate (SDS), dodecyltrimethylammonium bromide (DTAB), and cetylpyridinium chloride (CPC). The addition of co-solvents increased the critical micelle concentration (CMC), with 1-PrOH causing the largest increase due to its strong disruption of the hydrogen bonding network of water. Surface tension measurements revealed a decreased surface excess concentration ( Γ max ) indicating reduced surface adsorption. The minimum area per molecule ( A min ) increased with organic solvents, particularly in 1-PrOH-water mixtures, reflecting less efficient packing of the surfactant molecules at the surface. The packing parameter ( P ) decreased in mixed solvents, especially with 1-PrOH, suggesting a shift from spherical to elongated micellar structures. Aggregation numbers ( N agg ) were lower in mixed solvent systems, indicating smaller and less stable micelles. The free energy of adsorption ( ∆ G a d s o ${\increment}{G}_{ads}^{o}$ ) became less negative, indicating reduced spontaneity for micelle formation and adsorption, with the strongest impact seen in 1-PrOH. The overall trend of solvent effects was 1-PrOH > ACN > DMSO, highlighting the role of solvent polarity and amphiphilicity in altering surfactant behavior. These results provide valuable insights for the optimization of surfactant-based formulations.

A series of polycarbinol-siloxane surfactants with variations of two to six hydroxyl groups in the head structure and tri- and tetrasiloxane tail structures is synthesized, characterized and tested for foaming ability and fire suppression. The synthesis is practical, involving two steps, and produces products in high yield with good purity. The trisiloxane surfactants with 5 or 6 hydroxyl groups have sufficient water solubility, critical micelle concentrations, and display foaming ability levels to be effective in fire suppression testing. The tetrasiloxane surfactant with six hydroxyl groups was less soluble by a factor of 10 and did not exhibit sufficient foaming for effective fire suppression.

Emerging carbon capture, utilization, and storage (CCUS) technologies have driven the development of advanced nanocomposite materials. In this study, a novel polyhedral oligomeric silsesquioxane (POSS)-based nanomaterial, referred to as FAP, was synthesized using acrylamide, sodium α-olefin sulfonate, and tea saponin as monomers. The structure of the material was confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and silicon nuclear magnetic resonance spectroscopy ( 29 Si NMR), revealing a well-defined cage-like cubic architecture. TEM images clearly displayed the cage-like structure of the POSS material in FAP, while energy dispersive spectroscopy (EDS) confirmed the presence of silicon (Si) element. Thermogravimetric analysis (TGA) showed that the incorporation of POSS materials improved the thermal resistance of FAP. The nanomaterials significantly improved the foaming performance and foam stability. The foam generated by FAP reached a height of 480 mL, with a half-life of 10 h under conditions of 120 °C and a salinity of 100,000 mg L −1 , showing excellent properties. Furthermore, the foam was regenerable in the presence of 20 % kerosene and maintained good foaming performance. Microscopic mechanism analysis indicated that the POSS nanomaterials compressed the electrical double layer of the polymer, reduced the particle size, increased the liquid film thickness, and markedly improved the foam stability. Under the influence of activators, the gel viscosity of FAP exceeded 100 mPa s, which significantly improved the underground sealing efficiency of CO 2 . The novel nanocomposite material exhibited integrated capabilities for CO 2 foaming, foam stabilization, and storage. The optimal concentration of the FAP foaming agent was 0.75 %, resulting in a 32.75 % increase in recovery efficiency, a resistance factor of 18.9, and a CO 2 storage rate of 12.59 %. The development of this nanocomposite material provides technological support for effectively mitigation of CO 2 channeling during CO 2 flooding and promotes the wider application of CO 2 flooding technology.

The objective of the present study is to evaluate the binding properties of active pharmaceutical ingredients with mixture of surfactants with the aim of reducing the amount of the surfactants as well as the excipient for the pharmaceutical formulations and drug delivery applications. Therefore, a study of the interactions between the ionic surfactant sodium cholate (SC) and a cationic Gemini surfactant (12-2-12) in the presence of the drug propanolol hydrochloride (PH) in aqueous solution was carried out using conductance measurements. The effect of temperature and composition of the mixture was evaluated using critical micelle concentration (CMC) and other related parameters. For the mixture of SC + 12-2-12 in aqueous PH solution, the CMC of the mixed systems (CMC exp ) decreases with increasing temperature. However, at a fixed temperature, CMC exp tends to decrease with increasing mole fraction ( α 1 ), reaching a minimum at α 1 ≈ 0.7 and increasing thereafter. The ideal value of the CMC (CMC id ) is always higher than the experimental CMC exp , revealing synergistic interactions among the amphiphilic molecules studied. The free energy of micellization (Δ G o m ) is negative, while the enthalpy and entropy of micellization (Δ H o m and Δ S o m ) suggest the existence of hydrophobic interactions as the main driving force for micellization.

Eberconazole nitrate (EBN), a broad-spectrum imidazole antifungal agent, is widely used for the topical treatment of fungal mycoses. However, as a BCS class II drug, EBN faces problems such as poor skin permeability and low cutaneous bioavailability. To overcome these problems, a novel surfactant-based nanovesicular delivery system was developed. The aim of this study was to develop and evaluate a nanovesicular spanlastic gel loaded with EBN for sustained topical delivery and improved bioavailability. The EBN spanlastic vesicles were formulated using a modified ethanol injection method. Using a 2³ factorial design and Stat-Ease 360 ® software, eight formulations were evaluated to optimize particle size and entrapment efficiency. The vesicles exhibited nano size (93.5 nm – 368.6 nm) and high entrapment efficiency (94.14 % – 97.30 %). The optimized formulation had the smallest size and the highest entrapment efficiency. TEM analysis confirmed non-agglomerated circular vesicles. In vitro studies showed an enhanced drug release of 87.2 % within 8 h. The optimized spanlastic formulation was incorporated into a 1 wt% Carbopol 934 gel and tested for parameters such as viscosity, spreadability, drug content, skin irritation and in vitro release. Ex vivo permeation studies showed better drug release (97.3 %), higher flux (0.137 mg cm −2  h −1 ) and a higher permeability coefficient (0.0137) compared to conventional formulations. The results suggest that the nano spanlastic gel is a promising antifungal delivery system for EBN.

The increasing demand for environmentally friendly surfactants has led to the development of innovative, simplified and solvent-free synthesis methods. This study reports the preparation of 3-dimethylaminopropyl cocoyl betaine, a surfactant, using coconut oil refinery waste as the main raw material. A high yield of 90.46 % was obtained by a three-step esterification process using 3-dimethylaminopropanol and coconut oil deodoriser distillate. Structural analysis of the final product was carried out using NMR and Fourier transformation infrared spectroscopy, together with evaluation of the surfactant properties. The analysis of the surfactant properties of 3-dimethylaminopropyl cocoyl betaine indicated its potential suitability for use in personal care and cosmetic formulations. This study highlights the importance of reusing coconut oil refinery waste to produce environmentally friendly surfactants, supporting the chemical industry’s use of renewable and sustainable resources.