Volume 61, Issue 6

As the single largest class of specialty chemicals, surfactants are consumed in huge quantities in our daily life and in many industrial areas. In the past, the attention was focused entirely on technical performance. However, starting from the 1970s and 80s, surfactant related environmental concerns have become the main driving force to upgrade surfactant production technology to make more benign or “greener” products. For this reason, environmental issues, dermatological effects, and oral toxicity are the main priorities when surfactants are considered for a specific purpose. In this paper, we present five cases to demonstrate how the surfactant industry tackles these challenges to mitigate the environmental and health effects associated with surfactant consumption. We also discuss the important role played by surfactants in a current carbon capture and storage (CCS) strategy to reduce the CO 2 level in the atmosphere. Surfactant-based stable CO 2 foam flooding is a well-established enhanced oil recovery technique. It has been considered to be an economically realistic procedure to sequester large amounts of CO 2 in geological formations.

Critical micellar concentration (CMC) is a key physicochemical property of surfactants used to study their behaviour. This property is affected by factors such as temperature, pressure, pH, the type of organic solvent/water mixture, the chemical structure of the surfactants and the presence of electrolytes. Most of the existing studies in the literature have predicted the CMC under fixed conditions based on the chemical parameters of the surfactant. In this study, a machine learning approach using artificial neural network (ANN) models was used to estimate the CMC of some ionic surfactants. These models considered variables defining both the organic solvent-water mixture ( T , molecular weight, molar fraction and log P ) and the chemical structure of the surfactant (number of atoms of each element). A database consisting of a total of 258 CMC values for 10 ionic surfactants was collected from the literature. The ANN architecture consisting of an input layer with 12 neurons, an intermediate layer with 25 neurons and one neuron in the output layer is proposed. According to the results, the normalized ANN models provided the best statistical adjustments for the CMC prediction. These ANN models could be a promising method for CMC estimation.

The trimeric cetyl cationic surfactant (TGC) forms reversible photosensitive micelle systems with the photosensitive counterions trans -4-phenylazo benzoic acid ( trans -ACA). The Carreau-Yasuda model was used for the flow curves before and after UV irradiation. The effects of trans -ACA concentration, TGC concentration, and different durations of UV (365 nm) and visible light (465 nm) irradiation on the rheological properties of TGC/ trans -ACA were investigated. Prior to UV irradiation, the TGC/ trans -ACA system was composed of wormlike micelles, which showed pronounced shear thinning behavior, good thixotropy and viscoelasticity. Macroscopically, it appears as a difficult to flow solution. After UV irradiation, trans -ACA is isomerized to cis -ACA, and the worm-like micelles are transformed to spherical or short rod-like micelles, resulting in a significant decrease in thixotropy and viscoelasticity, and thus a decrease in viscosity and an increase in fluidity. At lower TGC concentrations, UV irradiation can induce a reversal of the rheological properties of the TGC/ trans -ACA system, which exhibits a complete solution state. Exposure to visible light restores the rheology of the system to that prior to UV irradiation. Under UV and visible light irradiation at different times, the system obeys to the rheo-kinetic equation. The UV–vis spectrum confirms that the changes in the rheological properties of the TGC/ trans -ACA system are due to the reversible photoisomerization of trans -ACA.

The structures and properties of different polyamide-11 (PA11) and organically modified Algerian clay nanobiocomposite systems are investigated in this work. The objective of this investigation is to evaluate the potential of modified Algerian clay as a nanofiller by studying of the properties of PA11/Mag-CTA nanobiocomposites with different levels of prepared fillers. Considering the different techniques used, the results show the full potential of the modified Algerian clay, with improvements in both thermal and mechanical properties after incorporation of the nanofiller (Mag-CTA). The intercalated and exfoliated morphology of the developed PA11 nanobiocomposites is demonstrated by the results of the different techniques used. The results indicate that the modified clay has a more significant impact on the thermal, mechanical, and rheological properties of the material than virgin polyamide-11 (PA11) at an equivalent rate of incorporation and low concentration. The optimal loading rate is estimated to be between 3 % and 5 % based on clay mass (Mag-CTA).

A triethanolamine-modified poloxamer temperature-sensitive hair care gel was formulated in order to reduce the adverse health effects associated with sodium thioglycolate (TGA(Na)), the active component in hair treatment agents, while maintaining excellent efficacy. It was found that TEA-3 gelled at 32 °C with a triethanolamine concentration of 3 %. This formulation exhibited a reversible phase transition, transitioning to a solid state upon contact with the scalp (>32 °C) and reverting to a liquid state when in contact with hair (<32 °C). The release behavior of TGA(Na) from the gel was assessed by both in vitro release studies and transdermal experiments. In addition, it was observed that the triethanolamine-modified poloxamer gel exhibited improved hair care efficiency compared to conventional hair care agents. These results suggest that the triethanolamine-modified poloxamer gel is a promising alternative to conventional hair care products, offering improved efficacy while minimizing potential adverse health effects.

Felodipine, a calcium channel blocker used to treat hypertension, is a BCS Class II drug characterized by low solubility, high permeability and significant hepatic metabolism, which limits its bioavailability to 15 %. This study focuses on improving the bioavailability of Felodipine by developing oral fast-dissolving films (OFDFs) incorporating lipid nanoparticles. Felodipine loaded lipid nanoparticles were prepared using glyceryl monooleate (GMO) as lipid and Poloxamer 407 as the surfactant, and then incorporated into OFDFs using the solvent casting technique. A Box-Behnken design with Design Expert Stat-Ease ® 360 was used to evaluate the impact of GMO, Poloxamer 407 concentration, and sonication time on particle size and entrapment efficiency. The resulting nanoparticle dispersions had particle sizes ranging from 74.92 nm to 112.1 nm and entrapment efficiencies between 80.43 % and 95.23 %. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) confirmed successful drug encapsulation. The OFDF showed optimal mechanical properties, disintegration within (41.33 ± 3.51) s, and an in-vitro drug release of (89.82 ± 2.75) % in 6 min. Scanning electron microscopy (SEM) revealed a smooth, uniform, porous surface and the films remained stable for three months. The study concludes that Felodipine loaded lipid nanoparticles in fast-dissolving OFDFs improve permeability, dissolution, and onset of action, making them a promising approach for antihypertensive therapy.

Palm fatty acid distillates can be used to produce fatty alcohol sulphates. The sodium hexadecyl sulphate (SHS) of the C 16 fatty acid thus formed has a high Krafft point which limits its use in applications. Here we propose the use of C 16 sulphate mixed with the amphoteric lauramidopropyl betaine (LAPB). The solubility of SHS in LAPB was determined and mixtures of the two were prepared to the extent of their solubility. The interfacial properties of the surfactant mixtures were investigated. The CMC of the surfactant mixtures was determined using dye solubilisation. The performance properties of the mixtures, such as foaming and viscosity, were analysed. It was concluded that the addition of even small amounts of SHS to LAPB causes a significant change in its CMC, although the performance properties of LAPB in terms of foaming and viscosity are maintained.

This paper describes an attempt to increase the sterilising efficacy of sodium hypochlorite (SH) by prolonging its shelf life in gel mode through the presence of wormlike micelles. No effect was observed on the presence of SH on the ratio of highest viscosity peak of 20:80 of 3 % (w/w) sodium dodecylsulfate (SDS) and cetyltrimethylammonium bromide (CTAB). On the other side, the presence of SH has a relatively negative effect on transformation process from spherical (three-dimensional, 3D) micelles to wormlike (one-dimensional, 1D) micelles. The gel state of the aqueous SH solution is maintained even at a ratio of 20:80 SDS:CTAB 3 % (w/w). Measurements of the biological activity of the gel using Staphylococcus aureus bacteria show that the sterilizing efficiency of SH is enhanced by the presence of 1D micelles. In contrast, the stability of SH using the kinetic method shows a sudden decrease in its stability due to the presence of 1D micelles, and the same is the case when both SDS and CTAB micelles are present. It was concluded that the increase in the biological activity of SH due to presence of micelles in gel or liquid mode resulted from their chemical interference, which acts as an antibacterial formulation.

In view of the simultaneous demand for surfactants and corrosion inhibitors in oilfield production, new surfactants with both low interfacial tension and corrosion inhibition function were successfully prepared in this work by amidation and carboxymethylation using fatty acids and amines as raw materials. The interfacial tension of the surfactant was investigated using a rotational interfacial tensiometer, and the critical micelle concentration was determined. The corrosion inhibition properties of the dual-functional agents were measured by weight loss experiments, electrochemical tests, and scanning electron microscopy (SEM). The results showed that the prepared surfactants exhibited interfacial tension as low as 10 −2  mN m −1 . The dual-functional surfactants possessed both low interfacial tension and promising corrosion inhibition effects. Electrochemical tests and SEM analysis showed that an adsorption layer preventing corrosion was formed on the surface of A3 steel. The adsorption of the dual-functional surfactants followed the Langmuir isotherm. The experimental data were also supported by quantum calculations.

In this study, a novel high salinity resistant, high temperature tolerant sulfonate Gemini surfactant (CK-3) for enhanced oil recovery was synthesized and is described. The critical micelle concentration (CMC) of CK-3 is 7.3 × 10 −5  mol L −1 with a surface tension at CMC, γ CMC , of 30.88 mN m −1 , and a pC 20 value of 4.80. Moreover, increasing temperature led to delayed micellization, indicating the superior surface activity inherent in Gemini surfactants. When CK-3 was evaluated as an imbibing agent, an interfacial tension of 8.3 × 10 −2  mN m −1 was observed between a 0.3 wt% CK-3 solution and crude oil, facilitated by hydrophobic group interactions which allow crude oil detachment. Finally, CK-3 molecules exhibited stable adsorption on rock walls, influencing wetting reversal. Zeta potential measurements exceeding 30 mV indicated stability. In aged capillary tubes, a 0.3 wt% CK-3 solution exhibited a rise height of 2.9 cm. Imbibition experiments on natural core samples showed a water imbibition efficiency of 8.73 %, compared to a significantly improved efficiency of 50.78 % with a 0.3 wt% CK-3 solution. This study also demonstrated the imbibition process and mechanisms of the CK-3, providing novel insights for the efficient development of unconventional oil reservoirs and the enhancement of crude oil recovery rates.

Since 1,2-distearoyl- sn -glycero-3-phosphocholine (DSPC), the component to keep structure of mRNA-lipid nanoparticle (LNP), is known to cause adverse effects, the replacement of DSPC with the combination of 1,2-distearoyl- sn -glycero-3-phosphoethanolamine (DSPE) and 1-stearoyl-2-hydroxy- sn -glycero-3-phospho ethanolamine (SHPE) was investigated. Specifically, when DSPC of mRNA-LNP was replaced by an 11:1 ratio of DSPE:SHPE, it was found that the size and permeability of mRNA-LNP were the same as those of mRNA-LNP containing DSPC in terms of stability. This result appears to be due to lipid geometry – the ratio of lipid volume to head group area and lipid length.