Pure N-Alkylaminopropionic Acid and N-Alkylaminodipropionic Acid Sodium Salts: Synthesis, Characterization, and Physicochemical Properties

Fourteen pure β-aminopropionic acid amphoteric surfactants were synthesized from methyl acrylate using primary amines. The synthesis was done in two steps. First, Michael addition of a primary amine to methyl acrylate gave two separable addition products. Second, because the resulting esters gave, by the classical saponification procedure, undesired retro-Michael products, they were treated with sodium trimethylsilanolate to give the corresponding pure anhydrous acid salt under mild non-aqueous reaction conditions. Two types of amphoteric surfactants were obtained: the monocarboxylate and the dicarboxylate series. The pure surfactants were characterized by IR, ¹H NMR, and ¹³C NMR spectroscopy. The surfactant critical micelle concentrations were evaluated. From these the Gibbs free energy of micellizations [∆G(–CH₂–)_mic] were calculated. These are related to the methylene units that contribute an average of −1.0 (±0.3) kJ mol⁻¹ for both the monocarboxylate and the dicarboxylate series.

Surfactant-Mediated Catalytic Determination of Fe(II) in Herbal and Pharmaceutical Products

In the present work, the catalyzed oxidation of neutral red (NR) by bromate was used to work out a kinetic-based analytical method as an alternative technique for the determination of Fe(II) in real and synthetic samples. A use of a surfactant, N-dodecylpyridinium chloride enhanced the sensitivity of the reaction by becoming involved in the reaction mechanism and providing a more suitable reaction environment. The iron-catalyzed oxidation of NR with potassium bromate was studied kinetically by using a fixed time method. The reaction was followed by measuring the decrease in absorbance at 535 nm. The use of a surfactant in the analytical run showed a five times increase in the sensitivity of the method. It served as a ready reservoir of NR by increasing its solubilization. The salt effect, pH, and reagent concentration were also investigated to achieve a more selective and sensitive analytical procedure. Under optimized conditions (4.2 × 10⁻⁵ mol L⁻¹ NR, 1.4 × 10⁻³ mol L⁻¹ KBrO₃, 1.5 × 10⁻² mol L⁻¹ cationic surfactant, 0.5 mol L⁻¹ LiCl and pH 2.60 at 30 °C), iron(II) was determined in the range 0.1–0.5 μg mL⁻¹ with a detection limit of 0.019 μg mL⁻¹ and a relative standard deviation (n = 6) 1.02% for 0.2 μg mL⁻¹ Fe(II). The influence of foreign ions on the accuracy of the results was investigated. The developed method is extremely sensitive, selective and simple. The method was applied successfully to the determination of iron in the herbal pharmaceutical and synthetic samples. The results showed good agreement with those obtained by atomic absorption spectrophotometry.

Synthesis, Characterization and Biological Activity of Sugar-Based Gemini Cationic Amphiphiles

Two series of gemini cationic surfactants were synthesized based on glucose and fructose molecules. Their chemical structures were confirmed using micro-elemental analysis, mass spectral fragmentation and FTIR spectroscopic analysis. The surface activities of these gemini amphiphiles were measured, including surface tension (γ), critical micelle concentration (CMC), effectiveness (π _cmc), efficiency (pC₂₀), maximum surface excess (Γ_max) and minimum surface area (A _min) at 25 °C. Adsorption and micellization free energies of these amphiphiles in their solutions showed a good tendency towards adsorption at the interfaces. The biological activity of the synthesized gemini amphiphiles showed good inhibition at concentrations of 1, 2.5 and 5 mg/mL. The synthesized amphiphiles showed antimicrobial activity on gram-positive and gram-negative bacteria and antifungal activity equal to or comparable to commercially available controls. The discussion rationalized the antimicrobial activities of these amphiphiles with the surface activity and the adsorption parameters. In addition, the effect of sugar nuclei was discussed based on the chemical structure of the bacterial and fungal cell membranes.

Adsorption of Anionic–Cationic Surfactant Mixtures on Metal oxide Surfaces

This research evaluates the adsorption of anionic and cationic surfactant mixtures on charged metal oxide surfaces (i.e., alumina and silica). For an anionic-rich surfactant mixture below the CMC, the adsorption of anionic surfactant was found to substantially increase with the addition of low mole fractions of cationic surfactant. Two anionic surfactants (sodium dodecyl sulfate and sodium dihexyl sulfosuccinate) and two cationic surfactants (dodecyl pyridinium chloride and benzethonium chloride) were studied to evaluate the effect of surfactant tail branching. While cationic surfactants were observed to co-adsorb with anionic surfactants onto positively charged surfaces, the plateau level of anionic surfactant adsorption (i.e., at or above the CMC) did not change significantly for anionic–cationic surfactant mixtures. At the same time, the adsorption of anionic surfactants onto alumina was dramatically reduced when present in cationic-rich micelles and the adsorption of cationic surfactants on silica was substantially reduced in the presence of anionic-rich micelles. This demonstrates that mixed micelle formation can effectively reduce the activity of the highly adsorbing surfactant and thus inhibit the adsorption of the surfactant, especially when the highly adsorbing surfactant is present at a low mole fraction in the mixed surfactant system. Thus surfactant adsorption can be either enhanced or inhibited using mixed anionic–cationic surfactant systems by varying the concentration and composition.

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The Interfacial Tension Between Cationic Gemini Surfactant Solution and Crude Oil

The effects of the hydrocarbon chains and spacer groups of gemini surfactants, salt, temperature, and polymer on the interfacial tension of crude oil–water mixtures were investigated in this paper. The length of the alkyl chain is a major factor affecting the properties of a gemini surfactant, and the spacer group is also an important factor influencing the surfactant properties. The addition of salt results in a great decrease in the CMC and favors the reduction of interfacial tension, which shows that a gemini surfactant has a good synergism with salt. Variation in temperature will affect the dynamic and equilibrium interfacial tension, and increasing the temperature can shorten the time to reach the equilibrium and decrease the equilibrium interfacial tension in the range of experimental temperatures. With the addition of polyacrylamide (PAM), it takes longer to reach equilibrium, but this has little effect on the value of equilibrium interfacial tension.

Micellization of Cetyl Triphenyl Phosphonium Bromide Surfactant in Binary Aqueous Solvents

The effect of the different binary aqueous organic solvents viz. 1,4-dioxane, acetonitrile, dimethylsulfoxide, ethylene glycol, and methanol, on the micelle formation and thermodynamics of a cationic surfactant cetyl triphenyl phosphonium bromide has been studied conductometrically at 298–318 K. From the conductivity data critical micelle concentration, degree of counter ion dissociation (α) and thermodynamic parameters of micellization have been determined. It is observed that micellization tendency of the surfactant decreases in the presence of binary aqueous solvents. The entropies of micellization are all positive, and they compensate the enthalpies of the process.

A 1D- and 2D-NMR Study of an Anionic Surfactant/Neutral Polymer Complex

NMR chemical shifts and linewidth measurements were examined for mixtures of sodium 10-phenyldecanoate (Na ω-PhDec) in deuterated aqueous solutions in the presence of varying compositions of poly(ethylene oxide) (PEO) polymers of 2000 and 4000 molecular weight. In addition, variable temperature NMR spectra and NMR spin lattice relaxation times (T ₁) were obtained for the PEO-4000/Na ω-PhDec system as a function of varying polymer concentrations. As expected, the polymer/surfactant systems exhibit the behaviour typical of that of an anionic surfactant/neutral polymer system with well defined critical aggregation concentrations (CMC) corresponding to the formation of polymer/surfactant complexes below the CMC of the free surfactant. The ¹H-NMR linewidths acquired for the Na ω-PhDec/PEO-4000 system before and after the CMC region of the surfactant indicate that the maximum in the linewidth of the PEO proton peak is reached at approximately twice the CMC of the free surfactant. 2D-NMR NOESY measurements on this system exhibit cross peaks between the PEO protons and the protons on the surfactant backbone, consistent with the location of the phenyl group in the micellar interior. All these NMR experiments are interpreted in terms of the structure of the polymer/surfactant complexes as a function of the system composition.

Synthesis of Cleavable Aryl Sulfonate Anionic Surfactants and a Study of their Surface Activity

A series of cleavable aryl sulfonate anionic surfactants were synthesized from cyanuric chloride, aliphatic amine and H-acid mono sodium salt. Their structures were identified by ¹H NMR, Infrared Spectrum (IR) and Elementary Analysis (EA). Their critical micelle concentrations (CMC) in aqueous solutions at 25 °C were determined by a steady-state fluorescence probe method and a surface-tension method. With the increasing length of the carbon chain, the value of their CMCs and surface tensions under CMC (γ _CMC) initially decreased and then reached a minimum (respectively 2.63 × 10⁻⁵ mol L⁻¹ and 28.29 mN m⁻¹) when the carbon number was 10. The CMC and γ _CMC then increased when the carbon number was increased to 12. The results showed that, compared with sodium dodecyl benzene sulfonate (SDBS), such kinds of surfactants have much lower surface adsorption amounts and greater molecular areas on the aqueous surface.

Degradation of Pesticides Wastewater by Silyl Based Cationic Surfactants

New stable silayl cationic surfactants have been studied for the destruction of toxic organophosphorus pesticides. Hexadecyl, dodecyl trimethyl silane ammonium chloride or iodide surfactants were synthesized and evaluated in the degradation of pesticides such as Diazinon, Malathion or Chlorpyrifos. The hydrolytic efficiency of each surfactant was tested by measuring the kinetics of model substrates cleavage under a pseudo-first order reaction. The iodo silayl based surfactants showed more destructive power than the chloro derivatives. Meanwhile, the hexadecyl moiety showed more effective pesticide degradation than the corresponding dodecyl moiety.

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Microwave Synthesis of Cationic Fatty Imidazolines and their Characterization

This paper describes an efficient method for the synthesis of long chain dialkyldiamido imidazolines by the reaction of diethylenetriamine and several fatty acids under non-solvent microwave irradiation using calcium oxide as support This synthesis required much less time in comparison to conventional thermal condensation and is carried out in an open vessel and the products obtained by this method were found to be in good yields and of high purity. Fatty imidazolines were then quaternized by using dimethyl sulfate as a quaternizing agent and isopropanol as a solvent, to produce cationic imidazolinium salts which were evaluated for yield and cationic content. The instrumental techniques, viz. FT-IR and ¹H NMR verified the formation of imidazolines and its subsequent quaternization. This method produced imidazolines in the very low time of 5–10 min and gave a yield of 89–91% as compared to a very long time of 8–10 h and a lower yield of 75–80% by the conventional thermal condensation method.

Spectrophotometric Determination of Cationic Surfactants Using Patent Blue V: Application to the Wastewater Industry in Algiers

Patent Blue V has been applied in a solvent extraction spectrophotometric method for the determination of cationic surfactants (CS) in industrial wastewaters. The method is based on the introduction of Patent Blue V as an anionic dye, and the formation of an ion pair association with CS in chloroform under the studied extraction conditions. The maximum wavelength of absorption for the ion pair is located at 627 nm, and a molar absorption coefficient of higher than 3.6 × 10⁵ l mol⁻¹ cm⁻¹ was obtained. The calibration curve was linear between 0 and 5.48 × 10⁻⁶ M, and exhibited a significant coefficient of correlation. Based on the calculated values for the relative standard deviation (%) over the studied concentration range, the method was found to be highly sensitive, and the deduced limit of detection for the method was found to be very low (8.6 × 10⁻⁸ M of CTAB). It was also found that a washing step was necessary for the organic extract in order to remove interferences caused by foreign ions and species present in unknown samples. To validate this method, the procedure was used to determine the CS contents of samples collected from textile industry wastewaters in the Algiers region. The results obtained showed good agreement for the proposed method.

Synthesis of Unsymmetrical Bolaform Surfactants with a Sulfonate Group and a Carboxyl Group

Three unsymmetrical bolaform surfactants with different aromatic rings and a ω-carboxyalkyl chain were synthesized and their molecular structures were characterized by ESI–MS and ¹H NMR. The percentages of conversion of alkylation were judged by the iodine value measurements and the effect of reaction temperature on sulfonate content of synthesized products has also been discussed.

The Synthesis of Oleic Acid Polyglycol Ester Catalyzed by Solid Super Acid

A SO₄ ²⁻/ZrO₂ super acid was prepared and the effect of different kinds of catalysts on the esterification reaction reviewed. The results showed that the SO₄ ²⁻/ZrO₂ super acid had higher catalytic activity and reactive selectivity in the synthesis of oleic acid polyglycol ester. Under optimum conditions the product was a monoester and the rate of production was more than 90%. The reaction product was characterized.

Investigation of the Structure-Directing Effect of Surfactants on the Distribution of Silicate Species Using <Superscript>29</Superscript>Si-NMR Spectroscopy

Silicate anions were studied using ²⁹Si NMR to investigate the structure-directing effect of a surfactant (sodium dodecylsulfate-SDS) on the distribution of silicate species present in alkaline silicate solutions. The distribution of the anions in the presence of polyelectrolytes was also investigated by ²⁹Si NMR through the use of different bases including tetramethyl ammonium hydroxide (TMAOH) and sodium hydroxide (NaOH). Both SDS and the polyelectrolytic solutions were shown to stabilize low molecular weight silicate species and thus inhibit polymerization.

Synthesis and Biological Activity of 8-Hydroxyquinoline and 2-Hydroxypyridine Quaternary Ammonium Salts

Two series of quaternary cationic surfactant were synthesized by reaction of 8-hydroxyquinoline and 2-hydroxypyridine with long chain alkyl halides (dodecyl, tetradecyl- and hexadecyl-bromide). Surface tension was measured in aqueous solution for different concentrations at 25 °C. Various surface properties of the synthesized surfactants were evaluated, particularly critical micelle concentration (CMC), efficiency (Π_CMC) as well as maximum surface excess (Γ_max) and minimum surface area (A _min). Micellization and adsorption in liquid/air interfaces thermodynamics were investigated. The synthesized cationic surfactants were evaluated for their biocidal activity. All compounds prepared showed good antibacterial and antifungal activities.

Effect of Selected Nonionic Surfactants on the Activated Sludge Morphology and Activity in a Batch System

In this study, two nonionic surfactants, one alcohol ethoxylate (AE) and one alkylphenol ethoxylate (APE) were investigated with regard to their influence on the morphology of activated sludge flocs, microbial activity and wastewater treatment efficiency in a laboratory batch system. The experiments were carried out for a range of nonionic surfactants concentrations in wastewater from 5 to 500 mg L⁻¹. Additionally, these results were compared to the data obtained in previous experiments on anionics and performed under the same conditions. Both nonionics tested caused a decrease in the size of activated sludge flocs but they did not affect the shape of the flocs. The circularity index and convexity of flocs remained similar to the control run, containing no surfactant. The presence of nonionic surfactants within the tested concentrations range caused a decrease in biomass activity. In spite of morphological changes of activated sludge flocs and a decrease in microbial activity, only higher concentrations of nonionics in wastewater starting with the level of 50 mg L⁻¹ can induce pinpoint flocs and decrease wastewater treatment efficiency. APE showed a stronger impact on the decrease in floc size and microbial activity than alcohol ethoxylate did. APE was also more difficult to biodegrade than AE. Comparing the efficiency of wastewater treatment (in terms of COD removal) in the presence of nonionic and anionic surfactants at the same concentration of 50 mg L⁻¹, the degree of organic pollutant removal was found to be higher by about 10% for anionics than for nonionics.

Synergistic Behavior of a Triblock Copolymer with Anionic and Cationic Surfactants in Aqueous Solution

The synergistic behavior of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer in aqueous solution with the synthesized anionic surfactants [decyl sulfonate (A10), myristyl sulfonate (A14) and cetyl sulfonate (A16)] and cationic surfactants [decyl pyridinium bromide (C10), myristyl peridinium bromide (C14) and cetyl pyridinium bromide (C16)] was investigated using a surface tension technique at 25 °C. The results show that the CMC values of binary mixtures for anionic and cationic surfactants with the triblock copolymer are lower than that of single surfactants. The synergistic interaction between surfactant molecules and copolymer molecules in binary mixed solution enhance the adsorption of surfactant molecules at the interface. The micellar mole fractions (X _m) and the interaction parameter (β) of these surfactants in mixed micelles were determined.

Electrostatically Shielded Quantum Confined Stark Effect Inside Polar Nanostructures

The effect of electrostatic shielding of the polarization fields in nanostructures at high carrier densities is studied. A simplified analytical model, employing screened, exponentially decaying polarization potentials, localized at the edges of a QW, is introduced for the ES-shielded quantum confined Stark effect (QCSE). Wave function trapping within the Debye-length edge-potential causes blue shifting of energy levels and gradual elimination of the QCSE red-shifting with increasing carrier density. The increase in the e−h wave function overlap and the decrease of the radiative emission time are, however, delayed until the “edge-localization” energy exceeds the peak-voltage of the charged layer. Then the wave function center shifts to the middle of the QW, and behavior becomes similar to that of an unbiased square QW. Our theoretical estimates of the radiative emission time show a complete elimination of the QCSE at doping densities ≥10²⁰ cm⁻³, in quantitative agreement with experimental measurements.

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Surface and Biological Activity of Some Novel Cationic Surfactants

In this study, steps were taken toward the development of bactericidal and fungicidal synthetic cationic surfactants by reacting decyl, dodecyl or tetradecyl amine with acetic or hydrochloric acid to produce a series of amine salts which consequently converted to copper or cobalt cationic complexes via complexing the first series compounds with copper (II) or cobalt (II) ions. Surface properties such as interfacial tension and emulsifying power of these surfactants were investigated. The surface parameters including critical micelle concentration (CMC), maximum surface excess (Γ_max) and minimum surface area (A _min) were studied. Free energy of micellization (ΔG°_mic) and adsorption (ΔG°_ads) were calculated. The antimicrobial activity was determined via the inhibition zone diameter of the prepared compounds, which measured against five strains of a representative group of microorganisms. FTIR spectra, elemental analysis and H¹ NMR spectrum were performed to confirm compound structure and purity.

Synthesis of Sulfated Sodium Salts of 1-Alkylamino-3-alkyloxy-2-propanols and N,N-Di-(2-hydroxy-3-alkyloxy propyl) Alkylamines as Potential Surfactants

1-Alkylamino-3-alkyloxy-2-propanols, V (a–g) and N,N-di-(2-hydroxy-3-alkyloxy propyl) alkylamines, VI (a–g) were prepared with the same chain length both for alkyl amino and alkyloxy groups by condensation of alkyl glycidyl ethers with long chain alkylamines by employing thermal and microwave-assisted methods. All the products were characterized by ¹H-NMR, IR and fast atom bombardment mass spectrometry studies. These compounds were further sulfated and evaluated as their sodium salts for surfactant properties namely surface tension, critical micelle concentration, emulsifying property, wetting, foaming power and calcium tolerance. Sulfated 1-dodecylamino-3-dodecyloxy-2-propanol, VII c and sulfated N,N-di-(2-hydroxy-3-dodecyloxy propyl) dodecylamine, VIII c were found to exhibit superior surfactant properties among the respective series of monomers and dimers.