The interaction between natural surface-active components in crude oil (asphaltenes and resins) at the emulsion interface is a central issue in regulating emulsion stability and demulsification. Herein, the influence of the structural features of surface-active components on the interactions between asphaltenes and resins was investigated based on several different crude oil surface-active component systems, aiming to identify the key structure governing their interaction. Asphaltenes and resins synergistically enhance the mechanical strength of interfacial film through it-it interactions and hydrogen bonding, thereby improving emulsion stability. The synergistic effect primarily stems from the chemical composition and spatial distribution of functional groups in the two components, wherein the abundant presence of hydroxyl and carboxyl groups serves as the key structure for strengthening their interaction. Furthermore, a small amount of highly hydrophilic sulfone-type sulfur accumulates at the oil-water interface due to their strong interfacial activity, further promoting the asphalteneresin interaction, thereby reinforcing the synergistic stabilization effect. Consequently, model oil emulsions stabilized by asphaltenes from Shengli crude oil enriched in hydroxyl, carboxyl, and sulfone-type sulfur groups exhibit stronger asphaltene-resin interaction and thus higher stability. In contrast, model oil emulsions stabilized by asphaltenes from Minghua crude oil containing less these functional groups show lower stability and are more prone to phase inversion. This interaction mechanism has been proven applicable to asphaltene and resin systems with different structural properties, and holds promise for universal applicability to more related research systems. This study can guide the controlled asphaltene-resin interaction, enabling precise regulation of crude oil emulsion stability and phase inversion. Future research still needs to verify the applicability of this mechanism in real crude oil systems and field conditions, and establish a universal influence mechanism.

Lubrication is often applied at interfaces where friction occurs upon relative motion. In boundary lubrication regimes, amphiphilic lubricant additives spontaneously adsorb onto the solid/liquid interfaces, tailoring surface properties and decisively dictating macroscopic lubrication performance. This process is essential for the proper functioning of machinery and for prolonging its service life. The molecular structure of amphiphilic compounds is a key determinant of their interfacial adsorption behavior, which directly influences lubrication quality.Recent advances in characterization techniques, particularly neutron reflection (NR) and small-angle neutron scattering (SANS), have enabled more precise analysis of the nanostructure self-assembled at interfaces from the amphiphilic molecules. These developments have provided new insights into the relationship between molecular structure, interfacial adsorption, and lubrication behavior, stimulating the growing interest in the design of lubrication systems that are novel, efficient, cost-effective, and environmentally friendly.This review summarizes recent experimental progress on the role of amphiphilic molecular structure in interfacial adsorption in both oil-based and water-based lubrication systems and its impact on lubrication. First, we discuss the interactions of amphiphilic molecules with particle surfaces in oil-based systems, including over-based detergent/dispersants, nanoparticles, and emulsion droplets. Next, we review the packing and structure-function relationship of these molecules at solid-liquid interfaces under friction and at gas-liquid interfaces in lubricant foams within oil-based systems. We also describe the behavior of amphiphilic molecules in water-based lubrication systems, including various surfactants and their experimentally revealed lubrication mechanisms. Finally, we outline current challenges and future directions for the development of amphiphilic lubrication additives.

To enhance the recovery efficiency of heavy oil, a nonionic Gemini surfactant (MOP-10) was successfully synthesized through a one-step reaction between maleic anhydride and octylphenol polyoxyethylene ether (OP-10). The surfactants before and after modification were systematically characterized and analyzed by means of surface tension measurement, interfacial tension test, contact angle measurement, diffusion-ordered proton nuclear magnetic resonance (1H NMR DOSY), and multiple light scattering (Turbiscan). The results demonstrated that MOP-10 exhibited a significantly lower critical micelle concentration (0.072 g/L) and superior interfacial activity, achieving an low interfacial tension of 8.04 × 10-2 mN/m, compared with OP-10. Meanwhile, MOP-10 shows a stronger wettability regulation capability at the solid-liquid interface, reducing the contact angle of the hydrophobic quartz surface to 14.81°. Furthermore, DOSY technology was employed to deeply investigate the molecular behavior of the surfactant prior to reaching the CMC, and the existence of preaggregates was confirmed. Microscopic oil displacement experiments demonstrate that MOP-10 can significantly enhance the heavy oil recovery rate to 73.69%, which is 14.23 percentage points higher than that of OP-10. The excellent performance of MOP-10 is mainly attributed to its Gemini structure, which endows the surfactant with stronger interfacial adsorption capacity, lower interfacial tension, and more efficient wettability reversal ability. This study reveals that MOP-10 has considerable application potential in heavy oil exploitation and provides a theoretical basis for the design and development of high-efficiency oil displacement agents.

Dyes with aromatic structures are known for their persistence and high toxicity. Once these dyes enter aquatic environments, they pose significant threats to both the ecosystem and human health. In this study, N,N-dimethylethylenediamine(DMEN) was used as a template to synthesize the ZIF-8 material, characterized by a high specific surface area and high mesoporosity. The hierarchical ZIF-8 material is utilized to remove dyes from simulated wastewater. It can adsorb organic dye molecules and harmful metal ions from dye-laden wastewater. And the two processes do not exhibit significant interference with each other. The results indicate that the hierarchical ZIF-8 exhibits excellent adaptability to wastewater environments with high salinity and extreme pH levels. The equilibrium adsorption capacity of hierarchical ZIF-8 for methylene blue is twice that of microporous ZIF-8, and its photocatalytic efficiency is enhanced by 30% compared to microporous ZIF-8. Moreover, the photocatalytic performance significantly improves under alkaline conditions: at a pH of 12, the degradation rate of methylene blue reaches 96.9%. The study found that hierarchical ZIF-8 primarily follows the photocatalytic reaction mechanism during the catalytic degradation of methylene blue. Hierarchical ZIF-8 demonstrates significant potential for application in textile wastewater treatment.

Functional polymers that simultaneously thicken water and reduce oil viscosity are increasingly vital in oilfield development. In this study, a comb-like amphiphilic polymer was constructed by free-radical copolymerization of a synthesized Gemini surfactant monomer with acrylamide and sodium p-styrenesulfonate (SSS), and this unique structure enhanced oil displacement performance. First, the structure of AASD-O10 was characterized using 1H NMR, FTIR, and TGA. The rheological properties, interfacial tension, wettability, emulsification, and viscosity reduction capabilities of AASD-O10 were also investigated. For comparison, copolymers HPAM, AAS, and AADO10 were also synthesized. At a concentration of 2 mg/mL, the interfacial tension of AAS, AAD-O10, and AASDO10 was 14.47 mN/m, 2.28 mN/m, and 2.23 mN/m, respectively. At NaCl concentrations of 50,000 mg/L and above, AASD-O10 reached an ultralow level, approximately 10-3 mN/m. AAD-O10 and AASD-O10 achieved a viscosity reduction rate of over 99 %. The wettability of HPAM, AAS, AAD-O10, and AASD-O10 was 111.35 degrees, 74.75 degrees, 54.10 degrees, and 38.50 degrees, respectively. The sand-packed tube experiments revealed that the polymers HPAM and AASD-O10 improve heavy oil recovery by 11.18 % and 19.64 %, respectively. Finally, the interaction mechanism between AASD-O10 and heavy oil asphaltenes was explored using XRD, SEM, and molecular dynamics simulations. The long hydrophobic chains and benzene ring structures in AASD-O10 can insert into the asphaltene lamellae, disaggregating asphaltene aggregates, which enhances the emulsification effect and subsequently reduces the viscosity of heavy oil. The reagents required for synthesizing AASD-O10 are all watersoluble, making the synthesis simple and cost-effective, and endowing it with significant potential for application in heavy oil exploitation.

Dye-containing wastewater (DCW) has become a serious environmental issue worldwide. In this work, thepoly(cyclotriphosphazene-co-2,4-diamino-6-phenyl-1,3,5-triazine) (PBMA) material was synthesized by precipitation polymerization method to probe the adsorptive removal of methylene blue (MB) from DCW. The adsorption conditions were optimized as pH = 7, initial MB concentration = 100 mg L-1, and adsorption time = 800 min. Based on the acid-base interaction, the MB molecules in the DCW was adsorbed over the surface of PBMA. The surface morphology, surface elemental composition and surface functional group changes of PBMA were monitored by scanning electron microscopy images, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy, respectively. The thermodynamic analysis showed that the removal of MB prefers a single-layer adsorption over PBMA surface according to the good fitness of the adsorption results by using Langmuir isotherm (R2 = 0.9906). The kinetic analysis revealed that the adsorptive removal of MB follows the pseudo-second-order kinetics, with intra-particle diffusion and external diffusion as the dominant factors. The PBMA maintained a high adsorption capacity even after undergoing five consecutive adsorption-desorption experiments (Over 90%). The development of polyphosphazene material provides potential application in the field of dye removal from DCW.

Improving the thickening and emulsification performances of cellulose nanocrystals (CNCs) is crucial for their effective application in enhanced oil recovery (EOR). In this study, three kinds of amphiphilic Cn-CNCs (n = 8, 12 and 16, n represents the number of carbon atoms in the alkyl chain) were successfully prepared by alkylationmodified CNCs. Compared to CNCs, Cn-CNCs exhibited a stronger performance of thickening the viscosity of aqueous phase, especially C12-CNCs. When the concentration was 1 wt% and at a fixed shear rate (10 rad/s), the viscosity of CNC dispersions was 13.1 mPa center dot s, while the viscosity of C12-CNC dispersions was 33.7 mPa center dot s. The enhanced thickening was attributed to hydrophobic association in addition to hydrogen bonding. In addition, C12-CNCs also exhibited superior emulsification performance due to the lower interfacial tension (IFT) and the thicker oil-water interfacial film. Furthermore, the oil displacement performance of C12-CNC dispersions was better than that of CNC dispersions, which was attributed to the improvement of sweep efficiency and oilwashing efficiency. This study provided the guidance for the effective application of CNCs in EOR.

Cellulose nanocrystals (CNCs) have attracted more and more attention in EOR. CNCs are abundant and renewable, with nanoscale dimensions, excellent rheological properties, and easy-to-modify surface properties. However, the colloid stability of CNCs under high salinity conditions is poor, which limits their application in enhanced oil recovery (EOR). In order to improve the stability of CNCs in the salt environment, the effect of the mixed system of sodium dodecyl benzenesulfonate (SDBS) and polyoxyethylene sorbitan monooleate (Tween 80) on the dispersion stability of CNCs in the presence of different valence salt ions was investigated systematically. The dispersion stability of CNCs was investigated by using the ζ-potential and dynamic light scattering (DLS) techniques. The mixed surfactants improved the dispersion stability of CNCs within the studied salt ion concentration range (Na+ ≤ 300 mM, Ca2+ ≤ 10 mM, Mg2+ ≤ 10 mM). The stabilization mechanism of CNCs was explained by the electrostatic effect and spatial stabilization effect. In the presence of salt ions, the adsorption behavior of mixed surfactants on the surface of CNCs in the presence and absence of crude oil was revealed through molecular dynamics (MD) simulations. Microscopic displacement experiments indicated that due to the small particle size of CNCs in salt environments, the pores were not blocked, resulting in a significant improvement in the oil displacement performance.

Emulsion catalysis, a subset of ’on-water’ catalysis, is influenced by surfactants that act as emulsion stabilizers. The hydrophobicity of these surfactants, closely tied to the molecular structure of their chains and their headgroup ionization, plays a crucial role in controlling emulsion reactions and subsequent processes of surfactant recovery and product purification. However, the influence of the specific chain structure of surfactants and its cooperation with the headgroup in different solution environments on the emulsion reaction and demulsification processes remains uncertain. In this study, the stability of emulsions stabilized by amino acid surfactants featuring various hydrophobic chains, specifically side chains, was studied across a range of pH conditions. Amino acid surfactants with long chain are pivotal in enhancing the stability of emulsions. The combined effect of hydrogen bonding and electrostatic interactions between the amino acid headgroups boosts the stability when the pH of the solution aligns closely with the pKa2 of the surfactants. Under these conditions, a relatively stable oil–water interface significantly increases the yield of the Knoevenagel reaction to 94 %. As the pH of the system increases, the surfactants become more hydrophilic, enabling the phase separation of the emulsion, which facilitates the collection of the product and the recycling of the surfactants. This study provides important insights on regulating the structure and function of the oil–water interface based on surfactants and proposes a potentially effective approach for environmental-friendly and convenient chemical synthesis.

The application of cellulose nanocrystals (CNCs) in enhanced oil recovery (EOR) is a developing hotspot. To improve the stability of CNCs in salt environments, the effects of sodium dodecylbenzene sulfonate (SDBS) and polyoxyethylene sorbitan monooleate (Tween 80) on the stability of CNCs in the presence of sodium (Na+), calcium (Ca2+) and magnesium (Mg2+) were investigated. The range of salt ions and the stability mechanism for improving the CNCs stability in the presence of SDBS and Tween 80 were pointed out. SDBS improved the stability of CNCs in the presence of 30-100 mM Na+, 1-2 mM Ca2+ and 2 mM Mg2+, respectively. Tween 80 improved the stability of CNCs in the presence of Na+ <= 300 mM, Ca2+ <= 10 mM and Mg2+ <= 10 mM, respectively. The mechanism was explained by the bridging effect of salt ions, electrostatic effect and spatial stability effect. The combined systems of surfactants (SDBS and Tween 80) with CNCs exhibited strong emulsifying properties, low interfacial tension (0.023 mN/m and 1.85 mN/m), and the ability to alter the wettability of oil wet rocks. This made the combined systems have better oil displacement performance.

Sphingosine, an amphiphilic molecule, plays a pivotal role as the core structure of sphingolipids, essential constituents of cell membranes. Its unique capability to enhance the permeability of lipid membranes profoundly influences crucial life processes. The molecular structure of sphingosine dictates its mode of entry into lipid bilayers and governs its interactions with lipids, thereby determining membrane permeability. However, the incomplete elucidation of the relationship between the molecular structure of sphingosine and the permeability of lipid membranes persists due to challenges associated with synthesizing sphingosine molecules. A series of sphingosine-derived molecules, featuring diverse hydrophobic chain lengths and distinct headgroup structure, were meticulously designed and successfully synthesized. These molecules were employed to investigate the permeability of large unilamellar vesicles, functioning as model lipid bilayers. With a decrease in the hydrophobic chain length of sphingosine from C15 to C11, the transient leakage ratio of vesicle contents escalated from ∼ 13 % to ∼ 28 %. Although the presence of double bond did not exert a pronounced influence on transient leakage, it significantly affected the continuous leakage ratio. Conversely, modifying the chirality of the C-3 hydroxyl group gives the opposite result. Notably, methylation at the C-3 hydroxyl significantly elevates transient leakage while suppressing the continuous leakage ratio. Additionally, sphingosines that significantly affect vesicle permeability tend to have a more pronounced impact on cell viability. Throughout this leakage process, the charge state of sphingosine-derived molecule aggregates in the solution emerged as a pivotal factor influencing vesicle permeability. Fluorescence lifetime experiments further revealed discernible variations in the effect of sphingosine molecular structure on the mobility of hydrophobic regions within lipid bilayers. These observed distinctions emphasize the impact of molecular structure on intermolecular interactions, extending to the microscopic architecture of membranes, and underscore the significance of subtle alterations in molecular structure and their associated aggregation behaviors in governing membrane permeability.

Amino acid surfactants play a crucial role in many personal care products and pharmaceuticals. Their significance arises from their unique characteristics, including diverse molecular structures, low skin irritation, and excellent biodegradability. The structure of amino acid surfactants, particularly the structure of their hydrophobic chains, plays a pivotal role in determining their interfacial properties. It is proposed that the steric hindrance effect stemming from the presence of branched hydrophobic chains can exhibit a profound influence on both the interfacial adsorption behavior and the overall performance of amino acid surfactants. We synthesized a range of novel amino acid surfactants featuring varying lengths of branched chains, derived from natural terpenoid alcohols. Several characterization techniques, including surface tension measurements, dynamic light scattering, foam volume assessments, demulsification time evaluations, and contact angle measurements were used to reveal the substantial influence of branched chains and the chain length on the surfactant performance. The investigation shows how the presence of branched chains influences their interfacial properties, their propensity to form larger aggregates above the critical micelle concentration and the impact of pH on the surfactants performance. Within the examined pH range, surfactants featuring natural branched farnesol chains exhibit critical micelle concentration ranging from approximately 0.8 to 3.8 mM. Those values are significantly lower when compared to surfactants possessing similar length of linear chains. Simultaneously, the conversion of linear hydrophobic chains into branched chains enhances the foam stability promoted by the surfactants by approximately 10 %. These findings emphasize the collective impact of hydrophobic interactions and steric hindrance of the hydrophobic chains on surfactant surface packing. The distinctive interfacial behavior exhibited by branched surfactants shows great potential in establishing a theoretical foundation for formulation research in the development of highly efficient detergents and premium cosmetics.

Surfactants facilitate the formation of crude oil emulsions in the petroleum reservoir and reduce oil-water interfacial tension, playing a crucial role in tertiary oil recovery. The host-guest interactions between β-cyclodextrin (β-CD) and surfactant molecules can regulate the solubility and hydrophobic interactions of surfactants, further regulating the interfacial and solution aggregation behaviors of the system. A ternary system composed of β-CD, nonionic surfactant Span 80, and anionic amino acid surfactant was designed to act as emulsion stabilizers and promote emulsion formation. Due to the pH responsiveness of the amino acid surfactant and host-guest interactions between the hydrophobic tail of the surfactant and β-CD, the emulsions exhibit dual responsiveness. The pH and β-CD host-guest interaction dual responsiveness determines the emulsion properties. By adjusting the proportion of β-CD in the ternary system and solution pH, the stability, droplet morphology, and rheological properties of the emulsions are all significantly affected. Interactions among emulsion stabilizers as well as their interfacial behaviors were analyzed using 1H NMR spectroscopy and interfacial tension analysis. This type of emulsion was also tested in core flooding experiments, clearly showing that the response of the emulsions to host-guest interactions can enhance crude oil recovery. Incorporating a higher concentration of β-CD into the system can boost additional secondary oil recovery by approximately 32%, while its pH responsiveness facilitates the demulsification of the system after the flooding. These research findings not only highlight the unique properties of the multi-responsive emulsion but also deepen our understanding of the interactions between surfactants. The ternary stabilizer system developed in this study demonstrates broad potential applications in flooding and oil-water separation.

Cellulose nanocrystals (CNCs) have been widely concerned in enhanced oil recovery (EOR) due to their abundant resources, small size and easy modification. In crude oil extraction, Fe (III) is increasingly produced. However, CNCs are very sensitive to Fe (III) and easy to aggregate, which brings obstacles to the application of CNCs. In order to improve the tolerance of CNCs to Fe (III), the surface of CNCs was modified with Aminopropyltrimethoxysilane (APTMS), N-[3-Trimethoxysilyl)propyl]ethylenediamine (TMPED) and N-[3-(trimeth-oxysilyl)propyl]diethylenetriamine (TMPDET), respectively. The products were named CNC-APTMS, CNC-TMPED and CNC-TMPDET. The N content in CNC-APTMS, CNC-TMPED and CNC-TMPDET are 1.36 wt%, 2.03 wt% and 2.17 wt%, respectively. The adsorption amount of Fe (III) by CNCs, CNC-APTMS, CNC-TMPED and CNC-TMPDETDT are ∼155 mg/g, ∼ 13 mg/g, ∼ 29 mg/g and ∼ 18 mg/g, respectively. This indicates that compared to CNCs, the modified CNCs improve significantly the tolerance to Fe (III). Moreover, compared to CNCs, in the presence of Fe (III), there is less remaining oil in the glass model after modified CNCs dispersion flooding. The improvement of tolerance to Fe (III) and the excellent oil displacement performance of the modified CNCs in the presence of Fe (III) make them the potential green oil displacement agents.

Interaction between surface active components in crude oils and nonionic surfactants plays an important role in phase inversion behavior of crude oil emulsion, while the interaction mechanism is not yet fully explored. Herein, the effects of nonionic surfactants on the synergistic interaction between asphaltene and resin, emulsion stability, and emulsion phase inversion were investigated. It is shown that the addition of Span 80 and Tween 80 promotes the reduction of phase inversion point of water in oil emulsion stabilized by asphaltene and resin, as well as increases the yield strain value of the emulsion. The addition of Tween 80 to the asphaltene and resin mixture reduces the inversion point from 70 % to 30 %. The decrease of phase inversion point is attributed to the difficulty in the formation of multiple emulsions after adding nonionic surfactants. The addition of nonionic surfactants can affect the hydrogen bonding between asphaltene and resin, thereby improving the emulsion stability. Span 80 coexists with asphaltene and resin at oil-water interface, reducing the Turbiscan Stability Index (TSI) of emulsion by 15 and improving the strength of the oil-water interface membrane. In comparison, Tween 80 with stronger hydrophilic ability dissolves asphaltene and resin into bulk phase, which leads to the oil-water interface occupied by a large amount of Tween 80. Its numerous EO groups result in the strong hydrogen bonding on the oil-water interface membrane, effectively increasing the strength of the oil-water interface membrane and reducing the TSI by 19. This work contributes to a better understanding of the phase inversion of crude oil emulsion and improves crude oil recovery.

Sphingosine plays crucial roles in various cellular functions. Deuterated molecules are widely used as the important tools to explore the structure, property, and function of biochemical materials. We here report a gram-scale synthesis of sphingosines with different deuterated chains. The synthesis started from different protiated fatty acids, which underwent hydrothermal platinum-catalyzed hydrogen/deuterium (H/D) exchange to produce the deuterated chains with different length. The Horner-Wadsworth-Emmons (HWE) coupling of a chiral amino acid derivative with the deuterated chains generated the unsaturated ketone precursors. The following stereoselective reduction via cyclic Felkin-Anh transition led to the desired anti-amino alcohol geometry. This efficient protocol enabled the gram-scale synthesis of the chain-deuterated sphingosines. The subsequent synthesis of the chain-deuterated derivatives, i. e. ceramide, sphinganine and sphingosine-1-phosphate, is also described. Their deuterium content was simultaneously characterized by H-1 NMR and high-resolution mass spectrum (HRMS).

Hypothesis: The milder interaction with biosystems makes the zwitterionic surfactants an important class of surfactants, and they are widely used in biological applications and in personal care formulations. An important aspect of those applications is their strong synergistic interaction with anionic surfactants. It is anticipated that the strong interaction will significantly affect the adsorption and self-assembly properties. Experiments: Surface tension, ST, neutron reflectivity, NR, and small angle neutron scattering, SANS, have been used here to explore the synergistic mixing in micelles and at the air-water interface for the zwitterionic surfactant, dodecyldimethylammonium propanesulfonate, C12SB, and the anionic surfactants, alkyl ester sulfonate, AES, in the absence and presence of electrolyte, 0.1 M NaCl. Findings: At the air-water interface the asymmetry of composition in the strong synergistic interaction and the changes with added electrolyte and anionic surfactant structure reflect the relative contributions of the electrostatic and steric interactions to the excess free energy of mixing. In the mixed micelles the synergy is less pronounced and indicates less severe packing constraints. The micelle structure is predominantly globular to elongated, and shows a pronounced micellar growth with composition which depends strongly upon the nature of the anionic surfactant and the addition of electrolyte. (C) 2022 Elsevier Inc. All rights reserved.

The catastrophic phase inversion process of model emulsions (water/Span 80-Tween 80/heptane) from oil-in-water to water-in-oil emulsion was investigated. During this process, the phase inversion of the emulsion was monitored through Fourier transform infrared spectroscopy (FT-IR). In emulsions without NaCl, oil-in-water gel emulsions are formed prior to phase inversion. As the HLB value increases, the oil volume fraction required for phase inversion becomes higher. Polydisperse distribution of the gel emulsion is observed from microscope optical images. The Turbiscan Lab stability analyzer indicates that O/W gel emulsions before the phase inversion has good stability at 50 °C. Rheological measurements reveal that emulsions exhibit non-Newtonian behavior. The viscosity of the gel emulsions increases significantly prior to phase inversion. As the oil volume fraction increases, the storage modulus and loss modulus of the gel emulsion increase to a maximum, at which catastrophic phase inversion occurs. In emulsions with NaCl, there is no oil-in-water gel emulsion formed before phase inversion. The physicochemical properties of the emulsion play a crucial role in whether gel emulsions are produced during catastrophic phase inversion. These gel emulsions have the potential to diversify the applications in crude oil extraction, drug delivery systems, packaging materials, and other fields.

The stability of an emulsion has an important effect on enhancing oil recovery. However, the effect of ions with different valences on the stability of the emulsion emulsified by an ionic surfactant is not fully understood. In this study, the effects of Fe(III) species on the stability, microscopic morphology of droplets, interfacial properties, and rheological properties of water-model oil emulsions emulsified by sodium dodecyl benzenesulfonate (SDBS) were explored. The effect of Fe(III) species on the stability of a W/O crude oil emulsion was also explored. The stability experiment results show that the addition of the Fe(III) species impairs the stability of the model oil-in-water (O/W) emulsion, in which the O/W model oil emulsion is inverted to a water-in-model oil (W/O) emulsion at ∼99 ppm. With the increase of Fe(III) species concentration, stable W/O model oil and W/O crude oil emulsions are obtained. The rheological results indicated that the existence of the Fe(III) species has a remarkable effect on the viscosity and viscoelastic behaviors of the water-model oil emulsion. The calculation results based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory are in accord with the stability experiment results. Furthermore, the addition of EO groups makes the phase inversion point appear at a higher Fe(III) species concentration, forming a more stable W/O model oil emulsion and a more unstable O/W model oil emulsion. The experimental results are helpful to comprehensively understand the effect of Fe(III) species on the stability of an emulsion emulsified by an anionic sulfonate surfactant, which can help to enhance the oil recovery.

Although surfactants have been widely used in skin care and other related applications, our knowledge about how surfactants interact with stratum corneum (SC) lipids remains limited. This work reports how surfactants interact with a lipid SC model by neutron diffraction and molecular dynamics (MD) simulations, focusing on examining the impact of surfactant molecular architecture. The surfactant-SC mixed membrane was constructed by an equimolar mixture of ceramide/cholesterol/fatty acids and surfactant at 1% molar ratio of total lipids. The arrangements of water and surfactant molecules in the membrane were obtained through neutron scattering length density (NSLD) profiles via contrast variation method, meanwhile, MD simulation clearly demonstrated the mechanism of hydration change in the surfactant-model SC mixed membrane. No drastic difference was detected in the repeating distance of the short periodicity phase (SPP) upon adding surfactants, however, it significantly enhanced the membrane hydration and reduced the amount of phase separated crystalline cholesterol, showing a strong dependence on surfactant chain length, branching and double bond. This work clearly demonstrates how surfactant architecture affects its interaction with the SC membrane, providing useful guidance for either choosing an existing surfactant or designing a new one for surfactant-based transdermal application.