Hydrophilic Head Research Articles

Inhibitive effect of anionic/zwitterionic hybrid surfactants on the self-corrosion of anode for alkaline Al-air battery

Surfactants have been increasingly used as corrosion inhibitors in recent years. The zwitterionic surfactants can keep their amphoteric characteristics within a wide range of pH and temperature. In this research work，the self-corrosion of Al anode in alkaline electrolyte for Al-air battery is suppressed by adding a hybrid corrosion inhibitor consisting of dodecyl dimethyl betaine (DDBT) and sodium dodecylbenzene sulfonate (SDBS). The hybrid surfactant behaves as an anodic inhibitor. The results show that the optimum inhibition efficiency is 91.27 % for 1 × 10−3 M DDBT + 4 × 10−3 M SDBS. The combination of DDBT and SDBS decreases the corrosion rate of AA5052 alloy in sodium hydroxide electrolyte. The hydrophilic heads of DDBT and SDBS can adsorb on surface. The long alkyl chains in surfactant bring an increase in hydrophobicity. The hybrid surfactants have the electrostatic interaction and hydrophobic interaction, which improving the inhibition effect for the hydrogen evolution reaction. In general, the mixture of anionic and zwitterionic surfactants can provide the potential for better inhibition performance and significance for practical application.

Locus lands biosurfactant loan and collaboration

The specialty chemical firm Locus Fermentation Solutions has secured $117 million to expand its biosurfactant business . The money comes in the form of an unusual loan that uses Locus’s intellectual property (IP), including more than 1,300 patents, as collateral. Locus uses custom microbial fermentation to produce specialty surfactants. Most of the firm’s products are based on sophorolipids, biosurfactants with hydrophilic sophorose sugar heads and various hydrophobic fatty acid tails. CEO Andy Lefkowitz says the loan will help pay for a capacity expansion underway that will triple overall factory space to 14,000 m 3 at Locus’s headquarters site in Solon, Ohio, and other locations. Locus is organized as a holding company with operating companies focused on different markets. Lefkowitz says the firm’s fastest-growing market is oil drilling and mining, where its surfactants can increase yields and lower carbon intensity. One of the companies, Locus Performance Ingredients, recently signed a pact

Mechanism research of SDBS-functionalized polypyrrole to improve electrochemical performance of screen-printed graphene electrode

A novel method to enhance the response sensitivity of screen-printed graphene electrode (SPGE) by modifying functionalized polypyrrole (PPy) is proposed. Functionalized PPy was synthesized at low temperature by doping sodium dodecyl benzene sulfonate (SDBS) using a non-covalent modification technique, and then modified on the surface of SPGE. Due to the introduction of hydrophilic heads dodecyl benzene sulfonate (DBS−), SDBS-functionalized polypyrrole exhibited a larger specific surface area and high dispersion. The structure and morphology of SDBS-functionalized polypyrrole were characterized by X-ray diffraction and scanning electron microscopy. The electrochemical behavior of SDBS-functionalized polypyrrole-modified SPGE (SDBS/PPy-SPGE) was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of potassium ferricyanide (K3[Fe(CN)6]). Compared with bare SPGE, the anodic currents sensitivity of SDBS/PPy-SPGE was improved from 11.38 μA·mM−1 to 15.17 μA·mM−1, and the oxidation current was increased by 78.06% in measuring 1 mM K3[Fe(CN)6] (PF). The adsorption energy and electron transfer of pure PPy and SDBS/PPy to PF molecules were calculated based on density functional theory (DFT). The adsorption energy (from -0.41 eV to -1.11 eV) and electron transfer (from 0.4 e to 0.56 e) of SDBS/PPy to PF molecules were significantly enhanced. These can be attribute to the large specific surface area, high dispersibility and chemical stability of PPy upon being non-covalently functionalized by SDBS. The electrochemical sensitivity and stability of SPGE was greatly enhanced by the synergistic effect of graphene and SDBS/PPy. Thus, SDBS-functionalized polypyrrole is a promising material for improving the electrochemical properties of electrode.

Spectral Characteristics and Functional Responses of Phospholipid Bilayers in the Terahertz Band.

Understanding the vibrational information encoded within the terahertz (THz) spectrum of biomolecules is critical for guiding the exploration of its functional responses to specific THz radiation wavelengths. This study investigated several important phospholipid components of biological membranes-distearoyl phosphatidylethanolamine (DSPE), dipalmitoyl phosphatidylcholine (DPPC), sphingosine phosphorylcholine (SPH), and lecithin bilayer-using THz time-domain spectroscopy. We observed similar spectral patterns for DPPC, SPH, and the lecithin bilayer, all of which contain the choline group as the hydrophilic head. Notably, the spectrum of DSPE, which has an ethanolamine head group, was different. Interestingly, density functional theory calculations confirmed that the absorption peak common to DSPE and DPPC at approximately 3.0 THz originated from a collective vibration of their similar hydrophobic tails. Accordingly, the cell membrane fluidity of RAW264.7 macrophages with irradiation at 3.1 THz was significantly enhanced, leading to improved phagocytosis. Our results highlight the importance of the spectral characteristics of the phospholipid bilayers when studying their functional responses in the THz band and suggest that irradiation at 3.1 THz is a potential non-invasive strategy to increase the fluidity of phospholipid bilayers for biomedical applications such as immune activation or drug administration.

Structural complexity and physical mechanism of self-assembled lipid as nanocarriers: A review

Lipids such as glyceryl monooleate, phosphatidylcholine, and monoglyceride (CITREM) possess an amphipathic property that allows them to self-assemble into a complex internal structure when interacting with an aqueous solution. Since amphiphilic molecules possess hydrophilic heads and lipophilic tails, hydrophobic effects cause the spontaneous activity of the molecular rearrangement. The self-organization of the molecules often results in the phases of lipid polymorphism, for example microemulsion, inverse bicontinuous cubic (Q2), discontinuous hexagonal (H2), and micellar cubic (I2) Fd3m. Interestingly, these lamellar and non-lamellar phases have been applied in the development of nanocarriers for drug delivery due to their ability to provide a sustained drug release system, better drug bioavailability, and improved overall treatment. However, the attention that they are receiving from their application is not comparable to our understanding of the mechanisms involved in their synthesis. Elucidation of the spontaneous process helps in predicting and tuning the internal structure of an amphiphilic molecule to suit its application. Therefore, this review discusses the formation of lipid polymorphism from the thermodynamic point of view, critical packing parameter, and modified stalk theory.

A novel class of phenylpyrazolone-sulphonamides rigid synthetic anticancer molecules selectively inhibit the isoform IX of carbonic anhydrases guided by molecular docking and orbital analyses

All the previously reported phenylpyrazoles as carbonic anhydrase inhibitors (CAIs) were found to have small sizes and high levels of flexibility, and hence showed low selectivity profiles toward a particular isoform of CA. Herein, we report the development of a more rigid ring system bearing a sulfonamide hydrophilic head and a lipophilic tail to develop novel molecules that are suggested to have a better selectivity toward a special CA isoform. Accordingly, three novel sets of pyrano[2,3-c]pyrazoles attached with sulfonamide head and aryl hydrophobic tail were synthesized to enhance the selectivity toward a specific isoform of human carbonic anhydrases (hCAs). The impact of both attachments on the potency and selectivity has been extensively discussed in terms of in vitro cytotoxicity evaluation under hypoxic conditions, structure–activity relationship and carbonic anhydrase enzyme assay. All of the new candidates displayed good cytotoxic activities against breast and colorectal carcinomas. Results of the carbonic anhydrase enzyme assay demonstrated the preferential of compounds 22, 24 and 27 to inhibit the isoform IX of hCAs selectively. Wound-healing assay has also been performed and revealed the potential of 27 to decrease the wound closure percentage in MCF-7 cells. Molecular docking and molecular orbital analysis have finally been conducted. Results indicate the potential binding interactions of 24 and 27 with several crucial amino acids of the hCA IX. Communicated by Ramaswamy H. Sarma

High frequency ultrasound for destruction of per- and poly- fluoroalkyl substances

Per- and poly-fluorinated substances (PFAS) are man-made chemicals, used for more than 50 years in plastics, waterproofing, non-stick pans, surfactants and aqueous firefighting foams. Due to their widespread use, and extreme persistence PFAS are now everywhere in the environment. However, PFAS are toxic, bioaccumulate in animals and plants and can lead to numerous ill-health effects. Many PFAS are now banned or heavily regulated and hence legacy and environmental PFAS require destruction. PFAS contain a hydrophobic fluorinated carbon chain and hydrophilic head group(s) giving them desirable chemical properties which also makes them extremely recalcitrant to typical degradation methods. This work will give an overview of how sonolytic degradation of PFAS is expected to be useful toward total remediation of environmental contaminations. We focus on high frequency ultrasound (1001,000 kHz) and examine parameters such as frequency, liquid height, power density, and reactor configuration. The approach will be discussed in reference to remediation samples of fire fighting foam and landfill leachate concentrate. Considerations of how high frequency ultrasound may be employed in an industrial setting will be discussed.

Guanidinium-Rich Lipopeptide-Based Nanoparticle Enables Efficient Gene Editing in Skeletal Muscles

Genome editing mediated by the CRISPR-Cas system holds great promise for the treatment of genetic diseases. However, safe and efficient in vivo delivery of CRISPR genome editing machinery remains a challenge. Here, we report a lipopeptide-based nanoparticle (LNP) that can efficiently deliver the CRISPR Cas9/sgRNA ribonucleoprotein (RNP) and enable efficient genome editing both in vitro and in vivo. An artificial lipopeptide, GD-LP, was constructed by linking a hydrophilic guanidinium-rich head to an oleic acid-based hydrophobic tail via a disulfide bond. LNP formed by the self-assembly of GD-LP can easily form a complex with RNP with a loading content of up to 20 wt %. The resulting RNP-LNP nanocomplex led to 72.6% gene editing efficiency in GFP-HEK cells with negligible cytotoxicity. The LNP also showed significantly higher transfection efficiencies than Lipofectamine 2000 for the delivery of mRNA in NIH 3T3 and RAW 264.7 and the delivery of plasmid DNA in B78 cells. In vivo studies showed that intramuscular injection of the RNP-LNP nanocomplex in Ai14 mice induced efficient gene editing in muscular tissues. Moreover, the delivery of Cas9 RNP and donor DNA by LNP (i.e., RNP/ssODN-LNP nanocomplex) restored dystrophin expression, reduced skeletal muscle fibrosis, and significantly improved muscle strength in a Duchenne muscular dystrophy (DMD) mouse model.

A Novel Surfactant with Short Hydrophobic Head and Long Hydrophilic Tail Generates Vesicles with Unique Structural Feature.

Surfactant molecules typically have a long hydrophobic tail and a short hydrophilic head group. It remains unexplored if surfactants can have a short hydrophobic head group and a long hydrophilic tail. Designing such surfactants is a challenge as a lengthy hydrophilic tail would completely solubilize the molecules. In this context, herein, the Fmoc-functionalized Gly-Pro-Hyp (GPO) tripeptide repeat-based molecule (Fm-GPO) with fluorenyl moiety as a short hydrophobic head and peptide as a long hydrophilic tail is demonstrated as a reverse surfactant at physiological pH, for the first time. π-π stacking of the fluorenyl moieties and intermolecular hydrogen bonding between the peptide chains with extended polyproline-II structure promoted the self-assembly into spherical vesicles with a unique feature of a large hydrophilic area in the interior and exterior of the bilayer. The current Fm-GPO system offers a new class of surfactants with unique features that can aid in the design of drug-loaded vehicles, which can be target-specific as the peptide chain can be manipulated with different functional ultra-short peptide sequences.

Sustained and Targeted Delivery of Self-Assembled Doxorubicin Nonapeptides Using pH-Responsive Hydrogels for Osteosarcoma Chemotherapy

While chemotherapeutic agents have particularly potent effects in many types of cancer, their clinical applications are still far from satisfactory due to off-target drug exposure, chemotherapy resistance, and adverse effects, especially in osteosarcoma. Therefore, it is clinically promising to construct a novel tumor-targeted drug delivery system to control drug release and alleviate side effects. In this study, a pH-responsive nonapeptide hydrogel was designed and fabricated for the tumor-targeted drug delivery of doxorubicin (DOX). Using a solid-phase synthesis method, a nonapeptide named P1 peptide that is structurally akin to surfactant-like peptides (SLPs) due to its hydrophobic tail and hydrophilic head was synthesized. The physicochemical properties of the P1 hydrogel were characterized via encapsulation capacity, transmission electron microscopy (TEM), circular dichroism (CD), zeta potential, rheological analysis, and drug release studies. We also used in vitro and in vivo experiments to investigate the cytocompatibility and tumor inhibitory efficacy of the drug-loaded peptide hydrogel. The P1 peptide could self-assemble into biodegradable hydrogels under neutral conditions, and the prepared drug-loaded hydrogels exhibited good injectability and biocompatibility. The in vitro drug release studies showed that DOX-P1 hydrogels had high sensitivity to acidic conditions (pH 5.8 versus 7.4, up to 3.6-fold). Furthermore, the in vivo experiments demonstrated that the DOX-P1 hydrogel could not only amplify the therapeutic effect but also increase DOX accumulation at the tumor site. Our study proposes a promising approach to designing a pH-responsive hydrogel with controlled doxorubicin-release action based on self-assembled nonapeptides for targeted chemotherapy.

Synergistic effects of Gemini cationic surfactants with multiple quaternary ammonium groups and anionic surfactants with long EO chains in the mixed systems

In this study, two different anionic surfactants containing long polyoxyethylene chains involving sodium fatty alcohol ether carboxylates (AE9C) as well as isomeric sodium fatty alcohol ether sulfates (iso-AE9S) are mixed with a new Gemini cationic surfactant bearing four quaternary ammonium groups (TC-GS). Then, the surface properties and aggregation behavior of the two mixed systems were investigated. The effect of the long polyoxyethylene chains on the conformation and hydration of the hydrophilic head group of AE9C and iso-AE9S weakened their negative charge density, thus hindering their excessive electrostatic adsorption with TC-GS and improving the stability of the mixed systems. The positive synergistic effects of TC-GS/AE9C and TC-GS/iso-AE9S exhibited significantly lower critical micelle concentration, faster diffusion rates, and superior wetting capability compared to single surfactants. The micellization process of both mixed systems is spontaneously enthalpy-driven, and the diffusion-adsorption process is consistent with the mixed diffusion-kinetic mechanism. Finally, both mixed systems are capable of forming complex and interesting aggregate morphologies, with TC-GS/AE9C can form multilayer spherical vesicles and TC-GS/iso-AE9S can form multicompartment concentric spherical vesicles.

An Inorganic-Organic Hybrid Framework Composed of Polyoxotungstate and Long-Chained Bolaamphiphile.

Surfactants are functional molecules utilized in various situations. The self-assembling property of surfactants enables several molecular arrangements that can be employed to build up nanometer-sized architectures. This is beneficial in the construction of functional inorganic-organic hybrids holding the merits of both inorganic and organic components. Among several surfactants, bolaamphiphile surfactants with two hydrophilic heads are effective, as they have multiple connecting or coordinating sites in one molecule. Here, a functional polyoxotungstate inorganic anion was successfully hybridized with a bolaamphiphile to form single crystals with anisotropic one-dimensional alignment of polyoxotungstate. Keggin-type metatungstate ([H2W12O40]6-, H2W12) was employed as an inorganic anion, and 1,12-dodecamethylenediammonium (C12N2) derived from 1,12-dodecanediamine was combined as an organic counterpart. A simple and general ion-exchange reaction provided a hybrid crystal consisting of H2W12 and C12N2 (C12N2-H2W12). Single crystal X-ray structure analyses revealed a characteristic honeycomb structure in the C12N2-H2W12 hybrid crystal, which is possibly effective for the emergence of conductivity due to the dissociative protons of C12N2.

Andrographolide-Soya-L-α-Phosphatidyl Choline Complex Augmented Solubility and Drug Delivery in Leishmania donovani, a Causative Agent for Cutaneous and Visceral Leishmaniasis.

The utility of andrographolide (AN) in visceral leishmaniasis (VL) and cutaneous leishmaniasis (CL) is limited owing to poor solubility, hindered permeation, and unstable structure under physiological conditions. The present study mainly focuses on synthesizing of andrographolide-Soya-L-α-phosphatidyl choline (ANSPC) complex in ethanol and its characterization using various spectral and analytical techniques. Results from FT-IR, 1H NMR, ROSEY, and in silico docking techniques suggest ANSPC complex formation due to inter-molecular interaction between the hydrophilic head of SPC and hydroxyl group of AN present at 24th position. ANSPC complex demonstrated the solubility of 113.93 ± 6.66μg/mL significantly (P < 0.05) greater than 6.39 ± 0.47μg/mL of AN. The particle size of ANSPC complex was found to be 182.2 ± 2.69nm. The IC50 value of AN suspension (PBS, pH ~ 7.4) at 24, 48, and 72h against Leishmania donovani (L. donovani) was noticed to be 32.76 ± 4.53, 20.87 ± 2.37, and 17.71 ± 3.06μM/mL, respectively. Moreover, augmented aqueous solubility of ANSPC complex led to significant (P < 0.05) reduction in IC50 value, i.e., 25.02 ± 4.35, 11.31 ± 0.60, and 8.33 ± 2.71μM/mL at 24, 48, and 72h, respectively. The IC50 values for miltefosine were noted to be 9.84 ± 2.65, 12.13 ± 7.26, and 6.56 ± 0.61μM/mL at similar time periods. Moreover, ANSPC complex demonstrated augmented cellular uptake at 24h as compared to 6h in L. donovani. We suppose that submicron size and phospholipid-mediated complexation might have endorsed the permeation of ANSPC complex across the plasma membrane of L. donovani parasite by transport mechanisms such as P-type ATPase. ANSPC complex warrants further in-depth in vivo studies under a set of stringent parameters for translating the product into a clinically viable form.

General adsorption isotherm for polyoxyethylene alkyl ethers CnEOm adsorbed at the water/air surface

An empirical adsorption isotherm model is presented based on fundamental thermodynamic equations of adsorption for the homologous series of the nonionic surfactants polyoxyethylene alkyl ethers (CnEOm) at the aqueous solution surface to determine the surface tension and surface pressure isotherms, surface equation of state, and molar characteristics for the adsorbed surfactant molecules. The new model describes the surface properties of CnEOm much better than the original Langmuir adsorption model used as thermodynamic basis. The analysis of the results shows that the increase of the alkyl chain length n (hydrophobic part) leads to an increase in the adsorption activity, while the increase of hydrophilic head group given by the number of EO units m, leads to a better solubility in water, and hence, to a smaller adsorbed amount. The results also show that the ethylene oxide group mainly influences the molar surface area.

Influence of the type and concentration of hydrocolloids on Ostwald ripening of emulsions stabilized with small molecular and non-ionic surfactants

The effects of hydrocolloid gum, gum arabic, carrageenan, and xanthan on the Ostwald ripening of emulsions fabricated using Brij or Tween surfactants were examined. Emulsions prepared using pure n-decane exhibited low stability to Ostwald ripening, and modifying the oil composition by mixing corn oil improved the stability to Ostwald ripening. When gums were added to emulsions prepared using pure n-decane, the stability to Ostwald ripening decreased further, except for xanthan in emulsions stabilized using Tween surfactant. This could be because gums may affect interactions between water molecules and the hydrophilic head of the surfactant, increasing the water solubility of n-decane. However, gum addition (or viscosity increment) increased the stability of emulsions prepared using the modified oil composition (90% n-decane and 10% corn oil). In conclusion, emulsions unstable to Ostwald ripening may be negatively affected by gum addition, whereas emulsions relatively stable to Ostwald ripening may be positively affected.

Influence of the Nature of the Lipid Building Blocks on the Second-Order Nonlinear Optical Responses of an Embedded Di-8-ANEPPS Probe.

The extensive collection of lipids found in cell membranes is justified by the fact that each lipid contributes to their overall structure, dynamics, and properties and so to the biological processes taking place within them. It also showcases that, in order to deepen our understanding of membranes, we need to have a tool to differentiate lipid bilayers of varying composition. In this work, we investigate a suite of single-component saturated glycerophospholipids varying only in their headgroup structure by analyzing the second harmonic generation (SHG) nonlinear optical (NLO) response of a probe, di-8-ANEPPS, embedded into the membranes. The seven hydrophilic heads chosen (phosphatidylcholine (PC), phosphatidylethanolamine (PE), diaglycerol (GL), phosphatidylserine (PS), phosphatidylglycerol (PG), phosphatidylinositol (PI), and phosphatidyc acid (PA)) represent all the major headgroups that are part of mammalian plasma membranes and provide an assortment of neutral, zwiterrionic, and charged species. First, molecular dynamics simulations revealed that the lipidic arrangement is strongly sensitive to the nature of the hydrophilic head and less to the variety in the hydrophobic region. Membranes exhibiting drastically opposite structural properties can be pointed out: 1,2-dihexadecanoyl-rac-glycerol (DPGL) is the thickest and most ordered and aligned system, whereas 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycerol) (DPPG) is thinnest and least ordered and aligned system. The structural analyses are then confronted with the molecular NLO responses, β, computed at the time-dependent density functional theory (TDDFT) level. As the orientation of the chromophore is impacted by the various degrees of order within the lipid bilayers, the diagonal component of the β tensor parallel to the bilayer normal, βZZZ, is as well. In the end, this computational approach provides insights into the link between lipid building blocks and the NLO responses of the embedded dye.

The surface energy and surface charge of microbubbles generated by frother surfactants

Microbubbles (MBs) in froth flotation have the important function of facilitating the collision and attachment between air bubbles and hydrophobic materials and subsequently recovering the hydrophobic materials. However, whether MBs can be generated in a flotation cell by adding frother surfactants is unknown. This study was designed to determine whether the two widely used frothers, methyl isobutylcarbinol (MIBC), representing alcohol frothers, and Dowfroth 250 (DF250), representing polyglycol ether frothers, could help generate MBs in a mechanical flotation cell. The underpinning air/water interfacial properties were also studied in the presence of the two frothers. The real time bubble size measurement demonstrated that MBs could be generated in the mechanical flotation cell in the presence of MIBC or DF250, and DF250 produced more and smaller MBs than MIBC. Air/water interfacial tension and microbubble zeta potential measurements indicated that the generation of MBs by MIBC and DF250 was primarily controlled by their ability in reducing surface tension. While DF250 formed premicellar aggregates at air/water interfaces and reduced surface tension significantly, MIBC only formed monolayers at air/water interfaces and reduced surface tension slightly. However, the slower adsorption of DF250 at air/water interfaces inhibited the generation of MBs to some extent. Compared with surface tension, surface charge played a secondary role in generating MBs. The adsorption of MIBC reduced the magnitude of surface charge of MBs, thus inhibiting the generation of MBs, while the adsorption of DF250 increased the magnitude of surface charge of MBs, enhancing the generation of MBs. The different behaviours of MIBC and DF250 in modifying interfacial properties and forming MBs were attributed to their unique structures. DF250 possesses a larger hydrophilic head and a longer hydrophobic chain than MIBC, and thus has a stronger ability to assist with the generation of MBs.

IMPROVING THE PERFORMANCE OF ZNO NANOPARTICLES FOR EOR IN HIGH-TEMPERATURE AND HIGH SALINITY CARBONATE RESERVOIRS

The main challenge of the application of nanofluids for enhanced oil recovery (EOR) in carbonate reservoirs is to maintain colloidal stability under reservoir conditions with high salinity and high temperature. In this study, we address this issue by increasing the stability and hydrophilicity of ZnO nanoparticles by adding TTIP. Adding TTIP on the surface of ZnO nanoparticles results in an increase in the hydrophilic heads in the final product. Then, these nanoparticles are used to coat carbonate rock surfaces to change their wettability. The coated rock plates are obtained by aging them in nanofluids. The modified ZnO-based coatings show to be more effective for wettability alteration purposes compared to the conventional ZnO coating. The un-coated rock plate is strongly oil-wet, where the water and n-heptane droplets contact angles on this surface are 168&amp;deg; and 0&amp;deg;, respectively. After aging the rock samples in nanofluids, superhydrophilic coatings form on the superhydrophobic surfaces. The rock surface before and after treatment, as well as the synthesized nanoparticles, are characterized by scanning electron microscope (SEM), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) analyses. Results of this study indicate the possibility of using the materials for wettability alteration of oil-wet carbonate rock in the EOR process. The results of core flooding tests demonstrate that the oil recovery enhances significantly through the nanofluid flooding.

Whippable emulsions co-stabilized by protein particles and emulsifiers: The effect of emulsifier type

Advancing an in-depth understanding of the stabilization mechanism of the whippable emulsions co-stabilized by protein colloidal particles and emulsifiers is necessary for the construction and modulation of emulsions suitable for a wider range of foods. In this study, four typical nonionic (GMS: glycerol monostearate, GML: glycerol monolaurate, Tween 60) or ionic (SSL: sodium stearoyl lactylate) small molecular weight emulsifiers (LMWEs) with partially different molecular structures were selected to fabricate low-saturated oil-in-water emulsions and emulsion foams together with zein colloidal particles (ZCPs), respectively. Particle size distribution, overrun, and creaming index were used to evaluate the stability and foaming ability of the whipping or whipped emulsions. In addition, percentage of adsorbed protein, zeta potential, and FT-IR were employed to investigate the effect of LMWEs on the stability of ZCPs at the oil-water or air-water interfaces, and the interaction between these two substances at the interfacial or molecular level. The results show that before aeration, all LMWEs can effectively assist ZCPs to stabilize emulsions and promote interfacial adsorption of ZCPs; however, only the emulsions containing nonionic emulsifiers can be further developed to the foams with higher overrun. Tween diminished the stability of whipped emulsions and the amount of ZCPs assembled at the interface. The interfacial stability of ZCPs is closely related to the length of the hydrophobic chain of LMWEs, as well as the size and polarity of hydrophilic heads, whereby possible mechanisms for the influence of different types of LMWEs on both interfaces in emulsions and foams are proposed.

Interfacial properties of cationic and anionic Gemini surfactant mixtures

AbstractThe possibility and the prospect of cationic/anionic (“catanionic”) surfactant mixtures based on sulfonate Gemini surfactant (SGS) and bisquaternary ammonium salt (BQAS) in the field of enhanced oil recovery was investigated. The critical micelle concentration (CMC) of SGS/BQAS surfactant mixtures was 5.0 × 10−6 mol/L, 1–2 orders of magnitude lower than neat BQAS or SGS. A solution of either neat SGS or BQAS, could not reach an ultra‐low interfacial tension (IFT); but 1:1 mol/mol mixtures of SGS/BQAS reduced the IFT to 1.0 × 10−3 mN/m at 100 mg/L. For the studied surfactant concentrations, all mixtures exhibited the lowest IFT when the molar fraction of SGS among the surfactant equaled 0.5, indicating optimal conditions for interfacial activity. The IFT between the 1:1 mol/mol SGS/BQAS mixtures and crude oil decreased and then increased with the NaCl and CaCl2 concentrations. When the total surfactant concentration was above 50 mg/L, the IFT of SGS/BQAS mixtures was below 0.01 mN/m at the studied NaCl concentrations. Adding inorganic salt reduced the charges of hydrophilic head groups, thereby making the interfacial arrangement more compact. At the NaCl concentration was above 40,000 mg/L, surfactant molecules moved from the liquid–liquid interface to the oil phase, thus resulting in low interfacial activity. In addition, inorganic salts decreased the attractive interactions of the SGS/BQAS micelles that form in water, decreasing the apparent hydrodynamic radius (DH, app) of surfactant aggregates. When the total concentration of surfactants was above 50 mg/L, the IFT between the SGS/BQAS mixtures and crude oil decreased first and then increased with time. At different surfactant concentrations, the IFT of the SGS/BQAS mixtures attained the lowest values at different times. A high surfactant concentration helped surfactant molecules diffuse from the water phase to the interfacial layer, rapidly reducing the IFT. In conclusion, the cationic‐anionic Gemini surfactant mixtures exhibit superior interfacial activity, which may promote the application of Gemini surfactant.