Synthesis,Characterization, Surface and Biological Activity of Diquaternary Cationic Surfactants Containing Ester Linkage

Two series of diquaternary cationic surfactants designated as E9Nm and E11Nm having two different alkyl chains in their chemical structure were synthesized. The chemical structures of these surfactants were confirmed using elemental analysis, FTIR and ¹H‐NMR spectra. The surface activities of the different surfactants were determined using surface and interfacial tension at 25 °C. The surface parameters including: critical micelle concentration, effectiveness, efficiency, maximum surface excess and minimum surface area were determined. The surface activities of the cationic surfactants were correlated with their chemical structure. The surface activities of the surfactants increased with increasing the hydrophobic chain length. The adsorption and micellization tendencies of the surfactants in solution were determined using the free energies of adsorption and micellization. The synthesized surfactants were evaluated as biocides against bacteria and fungi. Biocidal activity data showed that a gradual increase in the hydrophobic chain length of the surfactant molecules gradually increases the efficiency of these surfactants as biocides.     

Alanine-based surfactants: Synthesis and some surface properties

A homologous series of anionic surfactants, namely, sodium-N-(alkyloxycarbonyl) alanine (where alkyl=octyl-, dodecyl-, hexadecyl-, and octadecyl-) were synthesized having the formula: R-OCO-CH₂NH-CH₂-CH₂-COONa. Surface properties of their solutions, including surface tension, critical micelle concentration, effectiveness, maximum surface excess, and minimum surface area, were investigated for different concentrations at 25°C. The effects of these surfactants on the solubilization of a polar and a nonpolar solute were studied. Standard free energies of micellization and adsorption were calculated for the prepared surfactants in aqueous solution.     

Hydrotrope-Induced Enhancement of Room Temperature Surface Activity for High Krafft Point Fluorinated Surfactants

Potassium perfluorooctane sulfonate (KPFOS) and sodium perfluorooctane sulfonate (NaPFOS) exhibit poor surface activities in aqueous solution at room temperature because of their high Krafft points. In this work, we attempted to increase the solubility of KPFOS and NaPFOS and consequently improve their surface activities at room temperature with sodium p‐methylbenzene sulfonate (BS) and urea, which are typical hydrotropes in industrial applications. The effects of BS and urea on the surface tension of the aqueous solutions of KPFOS and NaPFOS were investigated at 25 °C. When the hydrotropes were added, the effectiveness of KPFOS and NaPFOS in surface tension reduction was greatly enhanced and KPFOS showed higher efficiency in surface tension reduction than NaPFOS. On the other hand, BS had much stronger ability than urea to reduce the surface tension of KPFOS and NaPFOS in water. In particular, with the assistance of BS the minimum surface tension of KPFOS approached 19 mN/m at 25 °C. It was worth noting that in the presence of BS, the surface tension of an apparently “saturated” solution (i.e., with coexisting surfactant solid) continuously decreased with increasing surfactant concentration. This behavior was ascribed to enrichment of branched PFOS isomers in aqueous phase with the assistance of BS, as evidenced by high‐resolution ¹⁹F NMR. Hydrotropes were able to recover the inherent character of KPFOS and NaPFOS as highly surface‐active fluorinated surfactants by increasing the solubility of branched isomers. This is an easy way to enhance the effectiveness in surface tension reduction at room temperature for fluorinated surfactants with high Krafft points.     

Synthesis, Surface and Thermodynamic Properties of Substituted Polytriethanolamine Nonionic Surfactants

Three series of nonionic surfactants derived from polytriethanolamine containing 8, 10, and 12 units of triethanolamine were synthesized. Structural assignment of the different compounds was made on the basis of FTIR and ¹H‐NMR spectroscopic data. The surface parameters of these surfactants included critical micelle concentration (CMC), surface tension at the CMC (γ_CMC), surfactant concentration required to reduce the surface tension of the solvent by 20 mN m^?1 (pC₂₀), maximum surface excess (Γ_max), and the interfacial area occupied by the surfactant molecules (A_min) using surface tension measurements. The micellization and adsorption free energies were calculated at 25 °C.     

Synthesis and solution properties of novel nonionic functional polyurethane surfactants

A series of novel nonionic functional polyurethane surfactants were synthesized by the polycondensation of 2,4‐toluene diisocyanate with poly(propylene oxide) (weight‐average molecular weight = 400, 1000, or 2000) and monoallyl‐end‐capped poly(ethylene oxide). The chemical structure of the polyurethane surfactants was determined by Fourier transform infrared and ¹H‐NMR, and the effects of the concentration, salt, rest time, and temperature on the surface tension were investigated. These polymeric surfactants exhibited excellent surface activity. Sample III, which was synthesized with monoallyl‐end‐capped poly(ethylene oxide) (number‐average molecular weight = 1000), poly(propylene oxide) (number‐average molecular weight = 2000), and tolylene diisocyanate, could reduce the surface tension to 37.6 mN/m at a concentration of 0.06 mol/L at 25°C. All polyurethane surfactants synthesized in this study had low critical micelle concentrations (ca. 10^?4 to 10^?5 mol/L) and could reduce the surface tension even at very low concentration levels. Moreover, the surface tension decreased with an increase in the temperature or the concentration of the polyurethane surfactants. The addition of salt resulted in a decrease in the surface tension, and it took some time for the polyurethane surfactants to reach a constant surface tension value. UV spectra were found to be very useful for determining the critical micelle concentration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2956–2962, 2006     

Synthesis, Surface, Thermodynamic Properties of Some Biodegradable Vanillin-Modified Polyoxyethylene Surfactants

Four water-soluble non-ionic ethoxylated surfactants based on vanillin were synthesized (VE₁₅, VE₂₀, VE₄₀, and VE₆₀). The chemical structures of these surfactants were confirmed using FT-IR and ¹H-NMR spectra. The molecular weights of the compounds were determined using viscosity measurements and gel permeation chromatography. Surface tension as a function of the concentration of the surfactant in aqueous solution was measured at 25, 40 and 55?°C. From these measurements, the critical micelle concentration (CMC), effectiveness (??_cmc), efficiency (pC₂₀), maximum surface (??_max) excess and minimum surface area (A _min), were calculated. The surface activity measurements showed their high tendency towards adsorption and micellization and their good surface tension reduction, and low interfacial tension. The emulsion stability measurements showed the applicability of these surfactants as emulsifying agents. The thermodynamic parameters of micellization (??G _mic, ??H _mic, ??S _mic) and adsorption (??G _ads, ??G _ads, ?S _ads) showed their tendency towards adsorption at the interfaces and also micellization in the bulk of their solutions. The biodegradability of the prepared surfactants was tested in river water using die-away method and showed their readily biodegradation in the open environment.     

Enzymatic preparation of polyethylene glycol esters of castor oil fatty acids and their surface-active properties

This study concerns the preparation and evaluation of nonionic surfactants prepared from polyethylene glycol (PEG) esters of castor oil fatty acid, a source of hydroxy fatty acid. A lipase-catalyzed esterification reaction has been employed to prepare PEG esters of hydroxy acid to overcome problems associated with chemical processes. Castor oil fatty acid (85% ricinoleic acid) was mixed with PEG of different molecular weight. Rhizomucor miehei lipase was added as catalyst (10% level) and the reaction was continued at 60°C under 2 mm Hg pressure for 360 min. Conversion of PEG to esters was in the range of 86–94%, depending on the molecular size of PEG. The products were isolated and examined for surface activity by surface tension measurement. Surface tension values measured at 25°C were about 36–37 dynes/cm.     

Synthesis and Surface Active Properties of Gemini Cationic Surfactants and Interaction with Anionic Azo Dye (AR52)

A homologous series of new gemini cationic surfactants were synthesized and characterized using micro elemental analysis, FTIR, ¹H-NMR and mass spectra. The surface activities of these amphiphiles were determined based on the data of surface tension. Critical micelle concentration, effectiveness of the surface tension reduction, efficiency of adsorption, maximum surface excess, minimum surface area and critical packing parameter were evaluated. The effect of cationic micelles on solubilization of anionic azo dye, sulforhodamine B (Acid Red 52) in aqueous micellar solution of the synthesized gemini cationic surfactants was studied at pH 6.9 ± 0.5 and 25 °C. The results showed that the solubility of dye rose with increasing surfactant concentration as a consequence of some association between the dye and the micelles. It was also observed that the aggregation of surfactant and dye takes place at a surfactant concentration below the CMC of the individual surfactant. The partition coefficients between the bulk water and surfactant micelles as well as the Gibbs energies of distribution of dye between the bulk water and surfactant micelles were calculated using a pseudo-phase model. The effect of the hydrophobic chain length of Gemini cationic surfactants on the distribution parameters was also reported. The results show favorable solubilization of dye in cationic micelles.     

Novel Imidazolium-Based Gemini Surfactants: Synthesis, Surface Properties, Corrosion Inhibition and Biocidal Activity Against Sulfate-Reducing Bacteria

Three novel imidazolium-based gemini surfactants had been synthesized and characterized using different spectroscopic techniques. The surface properties of the synthesized surfactants were determined using surface tension measurements at 20 °C. The surface parameters including critical micelle concentration (CMC), π _CMC, Pc₂₀, Γ_max and A _min were determined. The synthesized compounds were evaluated as corrosion inhibitors for carbon steel in 0.5 M HCl solution using the weight loss and polarization techniques. The biological activity of these surfactants was evaluated against sulfate reducing bacteria using most probable number method. The results indicate that the synthesized compounds have good surface properties and are proper corrosion inhibitors for low carbon steel, with a high inhibition efficiency observed around their CMC. These compounds exhibit a significant biocidal activity against sulfate reducing bacteria.     

Synthesis,Characterization, Surface,and Thermodynamic Studies of Alkyl Tetrachloroferrates: Performance Evaluation of Their Nanostructures as Biocides

Decyl and dodecylamino tetrachloroferrates were synthesized and characterized using Fourier-transform infrared spectroscopy (FTIR), elemental analysis, X-ray diffraction (XRD), nuclear magnetic resonance (¹H-NMR), and atomic absorption spectroscopy (AAS). The surface properties of the cationic surfactants including critical micelle concentration, effectiveness, minimum surface area, and maximum surface excess were determined using surface tension measurements. The effectiveness of surface tension reduction (π_cmc) was found to increase as the hydrophobic chain length increases with values of 30 and 34 mN m⁻¹ for C₁₀ and C₁₂, respectively. Moreover, the effect of temperature on micellization was determined over the range of 35–55 °C. Thermodynamic parameters (ΔG°, ΔS°, and ΔH°) were calculated and the results indicate a spontaneous process for both micellization and adsorption. The nanoparticles (NC₁₀ and NC₁₂) of the prepared surfactants were obtained using the ball mill technique. The particle size and morphology of the nanoparticles were determined using transmission electron microscope measurements. The antibacterial study of the nanoparticle surfactants revealed their strong efficiency against fungi and different pathogenic bacteria compared with the original surfactants.     

Surface adsorption in the mixtures of sodium dodecylsulphate and oxyethylenated nonylphenol with different oxyethylenation degrees

The effectiveness of surface adsorption in an aqueous solution of mixtures of surfactants composed of an anionic surfactant, sodium dodecylsulphate, mixed with a nonionic one, polyoxyethylenated nonylphenol, was studied. Their behavior was compared separately. This surface adsorption was characterized by the values of the surface tension at 25°C of the total concentrations below, but near to the critical micelle concentration (CMC) in the mixtures mentioned. These were obtained as a function of different proportions of surfactants in the mixture and different chain lengths of nonionic polyoxyethylenated surfactant. The total surface excess concentrations of the surfactant mixtures and the average of molecular area per surfactant species at the aqueous solution/air interface were calculated. Finally, the values were analyzed vs the above parameters. Presented at the XDCth Meetings of CED/AID, Granada, Spain, March, 1988.     

Bulk and interfacial physical properties of aqueous solutions of sodium lauryl sulphate and lauryl alcohol with air and benzene systems: Part II — mixed aqueous solutions of sodium lauryl sulphate and lauryl alcohol

The pH, density, bulk viscosity and electrical conductivity of aqueous solutions of mixtures of sodium lauryl sulphate and lauryl alcohol were measured for a range of concentrations at 25°C. The influence of interface age on the interfacial tension of mutually saturated benzene/aqueous solution surfaces is also reported. The effect of impurities on various physical properties was illustrated using an impure lauryl sulphate system. A detailed comparison of these data with those reported in the literature shows satisfactory agreement above the critical micelle concentration of the sodium lauryl sulphate in water. Current data in the premicellar concentration range reveal anomalous behavior. Data reported in the literature are summarized for the pH, density, bulk viscosity, electrical conductivity, surface tension, interfacial tension with benzene, surface excess concentration, surface shear viscosity, critical micelle concentration and molecular complex formation of the sodium lauryl sulphate/lauryl alcohol aqueous solutions. The interactions of the anionic-nonionic surfactants at fluid/fluid surfaces and their influence on the physical properties are examined. The use of such systems in the stabilization of dispersions is also discussed. Eighty-five references are cited.     

Mixed Micelles of Trisiloxane Based Silicone and Hydrocarbon Surfactants Systems in Aqueous Media: Dilute Aqueous Solution Phase Diagrams, Surface Tension Isotherms, Dilute Solution Viscosities, Critical Micelle Concentrations and Application of Regular Solution Theory

Mixtures of trisiloxane type nonionic silicone surfactant (SS) with sodium dodecylsulfate, tetradecyltrimethylammonium bromide or tert-octylphenol ethoxylated with 9.5 ethylene oxide groups were studied in water at 30 °C by dilute aqueous solution phase diagrams, surface tension and dilute solution viscosity methods. The cloud points for the silicone surfactant aqueous solutions increased upon addition of hydrocarbon surfactants indicating the formation of hydrophilic complexes in mixture solutions. The scrutiny of the surface tension isotherms plotted as a function of SS concentration revealed that competitive adsorption effects are the characteristic features in these mixtures depending upon the SS concentration. Otherwise the isotherms exhibited two break points and the difference of concentration between the two break points increased with the increase in SS concentration indicating the cooperative nature of interactions. The micellar mole fractions of individual surfactants were determined by Rublingh's regular solution theory; interaction parameters and activity coefficients were evaluated and interpreted in terms of synergistic type interactions in these mixtures. The surface active parameters in mixture solutions were estimated and their analysis shows that the molecular species in the mixture solutions have a preferential tendency for adsorption at the air/water interface than in association form in the bulk solution. The effect of hydrocarbon surfactants on the intrinsic viscosity of SS micelles was monitored and related to the enhanced hydration in mixed micelles.     

Surface tension,adsorption, and wetting behaviors of natural surfactants on a PTFE surface

The adsorption kinetics and wetting behaviors of three plant‐based natural surfactants (Reetha, Shikakai, and Acacia) on the polytetrafluoroethylene (PTFE) surface are reported in this study. Adsorption studies of these surfactants on PTFE surface show the equilibrium adsorption time is approximately 15 min, and Langmuir‐type isotherm fits well for all three surfactants. The contact angle measurements show that the value achieved by Reetha and Acacia solutions are close (～109°), but that is low in the case of Shikakai (98.13°). Although, comparing the adsorption densities of the surfactants at PTFE–water and air–water interfaces, it has been found that adsorption densities at the PTFE–water interface are low for all three surfactants than that of air–water interface. The alcohol–Shikakai mixed solutions show nonideal behavior of surface tension reduction through a strong interaction between alcohol and Shikakai molecules, which in turn, show lower surface tension and contact angle values than that of ideal. © 2014 American Institute of Chemical Engineers AIChE J, 61: 655–663, 2015     

Dynamic surface tension of aqueous surfactant solutions. 6. Compounds containing two hydrophilic head groups and two or three hydrophobic groups and their mixtures with other surfactants

Dynamic surface tensions (γ_t)—measured by the maximum bubble pressure method—of some surfactants containing two hydrophilic (sulfonate) groups and two or three hydrophobic groups in the molecule (“gemini surfactants”), and of their mixtures with a nonionic surfactant or an amine oxide, have been measured at 25°C in 0.1 M NaCl. Linearity of the plots of surface pressure vs. square root of the surface age indicated that the systems studied were all diffusion-controlled. For the individual surfactant systems, the apparent diffusion coefficient decreases with an increase in the number of alkyl chains and the bulkiness of the surfactant molecules. For the mixtures, when interaction between the two surfactants is weak, γ_t at short times (t<1s) is close to that of the component with the lower surface tension; at longer times, it is closer to that of the component with the lower equilibrium surface tension. When interaction is strong, γ_t at short times is greater than that of either component. The molar ratio at which maximum effect on γ_t is observed depends upon the strength of the interactions between the two surfactants.     

Enhanced oil recovery from high‐salinity reservoirs by cationic gemini surfactants

In order to enhance oil recovery from high‐salinity reservoirs, a series of cationic gemini surfactants with different hydrophobic tails were synthesized. The surfactants were characterized by elemental analysis, infrared spectroscopy, mass spectrometry, and ¹H‐NMR. According to the requirements of surfactants used in enhanced oil recovery technology, physicochemical properties including surface tension, critical micelle concentration (CMC), contact angle, oil/water interfacial tension, and compatibility with formation water were fully studied. All cationic gemini surfactants have significant impact on the wettability of the oil‐wet surface, and the contact angle decreased remarkably from 98° to 33° after adding the gemini surfactant BA‐14. Under the condition of solution salinity of 65,430 mg/L, the cationic gemini surfactant BA‐14 reduces the interfacial tension to 10^?3 mN/m. Other related tests, including salt tolerance, adsorption, and flooding experiments, have been done. The concentration of 0.1% BA‐14 remains transparent with 120 g/L salinity at 50 °C. The adsorption capacity of BA‐14 is 6.3–11.5 mg/g. The gemini surfactant BA‐14 can improve the oil displacement efficiency by 11.09%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46086.     

Retracted: Synthesis,Characterization, and Surface Activities of Polymeric Cationic Thiol Surfactants in Aqueous Medium

A series of cationic polyurethane surfactants [PQ_8-18] were synthesized by the reaction of alkyl bromoacetate (namely: octyl-, decyl-, dodecyl-, tetradecyl-, hexadecyl-, and octadecyl bromoacetate) as quaternizing agents and modified polyurethane contains tertiary amine species. Modified polyurethane was prepared by the reaction of toluene diisocyanate (TDI) and triethanol amine monomercaptoacetate. The chemical structures of the prepared surfactants were confirmed using elemental analysis, Fourier transform infrared spectroscopy (FTIR), and Proton nuclear magnetic resonance (¹H NMR) spectroscopy. The molecular weight measurements of the prepared polymers showed that the segments of each polymer contain average 10 units of the urethane-triethanol amine mercaptoacetate. The surface activities of the prepared surfactants including: surface tension (γ), effectiveness ( π_cmc), concentration at micelle formation (CMC), efficiency (Pc₂₀), maximum concentration at the interface (Γ_max), and the average area occupied by each surfactant molecule at the interface at equilibrium ( A _min) of surfactants solutions were established at 25°C. The surface tension and the critical micelle concentration values of the prepared surfactants were gradually decreased by the gradual increase of their alkyl chain length. The prepared cationic surfactants showed efficient activity as inhibitors for dissolution of carbon steel in an acidic medium and also as a biocide against the growth of bacteria, fungi, and yeast.     

Synthesis and Surface Properties of Novel Gemini Imidazolium Surfactants

Five new Gemini imidazolium surfactants were synthesized from imidazole and 1-bromoalkane (C₈, C₁₀, C₁₂, C₁₄, C₁₆) to get 1-alkylimidazole, which was further reacted with 1,3-dichloropropan-2-ol to form the surfactant molecule, 1,1′-(propane-1,3-diyl-2-ol) bis(3-alkyl-1H-imidazol-3-ium) chloride. The structures of the five new surfactants and intermediates were characterized by ¹H-NMR, ¹³C-NMR and IR spectra. Thermal properties of the five new surfactants were studied with thermogravimetric analysis and differential scanning calorimetry, the five new surfactants showed a transition from a crystalline phase to a thermotropic liquid–crystalline phase at around ca. 100 °C, which transformed to an isotropic liquid phase at around ca. 165 °C. The five new surfactants critical micelle concentrations (CMC) in the aqueous solutions were determined by surface tension and electrical conductivity methods. The surface tension measurements provided a series of parameters, including critical micelle concentration (CMC), surface tension at the CMC (γ _CMC), adsorption efficiency  (pC ₂₀), and effectiveness of surface tension reduction (π_CMC). In addition, with application of the Gibbs adsorption isotherm, maximum surface excess concentration (Γ_max) and minimum surface area/molecule (A_min) at the air–water interface were obtained. The parameters β (degree of counterion binding to micelles), ΔG _ads ^θ (Gibbs free energy of adsorption), and ΔG _mic ^θ (Gibbs free energy change of micellization) were also derived. The results indicated that the five new Gemini surfactants exhibited very low CMC and a good efficiency in lowering the surface tension of water. The foamability and foam stability of the five new surfactants were also examined at different CMC.     

Influence of Temperature on the Surface Tension of Triton Surfactant Solutions

The surface tension of different Triton surfactants (X-100, X-405, and X-705) with or without adding sodium chloride was measured in the temperature range between 20 and 40°C using the maximum bubble pressure method. Rising temperature reduced the surface tension of Triton surfactants via disrupting the H-bonds between the ethylene oxide (EO) group and water. Increasing the number of the EO groups created the steeper thermal gradient of the surface tension. The data indicated that EO-water bonds are easier to be broken by rising temperature than the water–water H-bonds, with an entropy change of −0.535 J deg⁻¹ per mole of EO. The presence of NaCl decreased the surface tension for all systems. However, NaCl produced a synergistic effect with surfactants on the surface tension.     

Synthesis and Properties of Alkoxyethyl β‐d‐Xylopyranoside

In order to improve the water solubility of sugar‐based surfactants, alkyl β‐d‐ xylopyranosides, novel sugar‐based surfactants, 1,2‐trans alkoxyethyl β‐d‐ xylopyranosides, with alkyl chain length n = 6–12 were stereoselectively prepared by the trichloroacetimidate method. Their properties including hydrophilic–lipophilic balance (HLB) number, water solubility, surface tension, emulsification, foamability, thermotropic liquid crystal, and hygroscopicity were investigated. The results indicated that their HLB number decreased with increase of alkyl chain, the water solubility improved since the hydrophilic oxyethene (─OCH₂CH₂─) fragment was introduced. The dissolution process was entropy driven at 25–45 °C for alkyl chain length n = 6–10. Octyloxyethyl β‐d‐ xylopyranoside had the best foaming ability. Nonyloxyethyl β‐d‐ xylopyranoside had the best foam stability and the emulsifying ability was better in toluene/water system than in rapeseed oil/water system. The surface tension of in aqueous solution dropped to 27.8 mN m^?1 at the critical micelle concentration, and it also showed the most distinct thermotropic liquid phases with cross pattern texture upon heating and the fan schlieren texture on cooling. Hexyloxyethyl β‐d‐ xylopyranoside possessed the strongest hygroscopicity. Based on the effective improvement of water solubility, the prepared alkoxyethyl β‐d‐ xylopyranosides showed excellent surface activity and are expected to develop their practical application as a class of novel sugar‐based surfactants.