Formulating Alcohol-Free Microemulsions Using Rhamnolipid Biosurfactant and Rhamnolipid Mixtures

This research focused on developing alcohol-free biosurfactant-based microemulsions. Rhamnolipid-based mixtures were found to have double the solubilization parameter as compared to sodium bis(2-ethyl) dihexyl sulfosuccinate/sodium dihexyl sulfosuccinate/sodium mono- and dimethyl naphthalene sulfonate at the same total molar concentration. For the first time, a phase diagram was developed for surfactant mixtures containing soy methyl ester ethoxylate, rhamnolipid and oleyl alcohol with limonene oil. This phase diagram can be used as a guideline for selecting a surfactant system and surfactant ratio to formulate microemulsions with a given oil. In addition, the alcohol-free biosurfactant-based microemulsions required reasonable salinity values for limonene, making it viable in a variety of applications.

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.

---

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.

Synthesis and Physicochemical Investigation of Long Alkylchain Betaine Zwitterionic Surfactant

An effective and economic two-step route was developed to synthesize the long alkyl chain betaine zwitterionic surfactant directly from natural fatty acids. The optimal processing conditions for synthesizing the intermediate and final product were probed and the yields of 96.4% and 88.3% were obtained for each step, respectively. The surface active behavior of the synthesized decylbetaine surfactant was investigated using the surface tension method. The related thermodynamic parameters were calculated and discussed. The fluorescence probe technology was applied to determine the micropolarity of decylbetaine micelles.

Enhancement of the Antitumour Activity for the Synthesised Dodecylcysteine Surfactant using Gold Nanoparticles

In this paper, the surfactant dodecylcysteine hydrochloride was synthesised. The surface parameters of the synthesised surfactant were studied using a surface tension technique. The surface parameters show a good surface activity of the prepared surfactant in aqueous solution. The self-assembling behaviour of the synthesised surfactant comparing with that of cysteine compound on the prepared gold nanoparticles was confirmed using transmission electron microscope (TEM) measurements. The effect of self-assembling of this surfactant on the size of gold nanoparticles was studied using TEM images. The antitumour activity of the prepared surfactant without and with the gold nanoparticles was investigated. The results show that the antitumour activity of the prepared surfactant was enhanced with the presences of the gold nanoparticles.

Analysis of Linear Alkylbenzene Sulfonate in Waste Water and Sludge by High Performance Liquid Chromatography: An Exercise of Validation

Linear alkylbenzene sulfonate (LAS) an ingredient of many household and industrial detergents can reach the environment after disposal of raw sewage. Its correct detection and quantification in different environmental samples is a critical issue for evaluating its environmental fate. This paper outlines a validation of an entire analytical procedure of LAS in environmental samples, including extraction, pre-concentration and HPLC detection and quantification with fluorescence detection.

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.

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.

Comparison of QSAR and QSPR Based Aquatic Toxicity for Mixed Surfactants

In the present study, quantitative structure-activity relationship (QSAR) equations were derived using the logarithm of the octanol/water partition co-efficient for the prediction of acute aquatic toxicity of mixed surfactant systems. Further mixed surfactant systems of an anionic surfactant (sodium lauryl sulfate) and several nonionic surfactants (alkyl polyglucoside) of different hydrophobic chain lengths were taken together to calculate the parameter pEC50. Quantitative structure-properties relationship (QSPR) equations based on pC20, and A _min were developed from the surface tension data to predict pEC50 values and compared with QSAR derived pEC50 values to understand the probable mechanisms of action of the mixed surfactants blends for aquatic toxicity. The established QSAR and QSPR equations for mixed surfactants indicate that given blends of surfactants act as a polar narcotic.

Microwave-Assisted Synthesis and Properties of a Novel Cationic Gemini Surfactant with the Hydrophenanthrene Structure

A novel cationic gemini surfactant with the hydrophenanthrene structure has been synthesized from dehydroabietic acid by use of conventional thermal conditions and microwave irradiation. Its structure was confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy. It was found that microwave-assisted synthesis is an efficient means of preparation of this cationic gemini surfactant, with shorter reaction times and higher yields. The title compound had high surface activity. The CMC was 3.1 × 10⁻⁵ mol L⁻¹, γ _CMC was 26.3 mN m⁻¹, and emulsifying power (with benzene) reached five days. Comparison of this gemini surfactant and its monomeric counterpart proved the gemini surfactant was more surface active.

Synthesis,Surface Properties and Antimicrobial Activity of Bolaamphiphile/Oppositely Charged Conventional Surfactant Mixed Systems

Four ionic bolaamphiphiles were synthesized from four bolasingle systems and the surface properties of bolasingle systems and bola\oppositely charged conventional mixed surfactant systems were studied. Variations in the structure of the hydrophobic chain of bolaamphiphiles has a great influence on their antimicrobial activities. The bolaform surfactants prepared have significant antimicrobial and antifungal activities relative to their conventional analogues. The Г_∞ (saturated adsorption amount) and A _min (minimum average area per surfactant molecule) of these bolaamphiphiles in both water and 0.1 M NaCl solutions were calculated and CMC of the mixed systems with oppositely charged conventional surfactants in both water and 0.1 M NaCl solutions were determined.

Interaction Between an Anionic and an Amphoteric Surfactant. Part II: Precipitation

Use of amphoteric and anionic surfactants is very common in practical formulations such as shampoos and hand dishwashing products. Precipitation of mixtures of dimethyldodecylamine oxide (DDAO) as an amphoteric surfactant and sodium dodecyl sulfate (SDS) as an anionic surfactant were studied at different pH levels. The DDAO is a pH-sensitive surfactant and its protonation can be expressed in terms of a pK _a similar to an acid dissociation constant. The protonated form of DDAO carries a positive charge and precipitates with the oppositely charged SDS. Therefore, precipitation phase boundaries are pH dependent due to the varying degree of DDAO protonation. By combining the use of regular solution theory and the pseudophase separation model to describe micellar mixing nonidealities with the precipitate solubility product constant and the protonation dissociation constant, a model to predict the precipitation phase boundary is presented here. The model agrees well with experimental phase boundaries at different pH levels.

The Synergism Effect Between Sodium Dodecylbenzene Sulfonate and a Block Copolymer in Aqueous Solution

The synergistic behavior of sodium dodecylbenzene sulfonate (SDBS) with poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) block copolymer was studied using surface tension measurements. The surface tension of single and mixed solutions of SDBS and the block copolymer in this study was measured at different concentrations and at 25 °C. The critical micelle concentration (CMC) of these solutions was determined from the surface tension measurements. The SDBS gives higher CMC values than those of the block copolymer. The results show that the CMC value of SDBS decreases as the molar ratio of SDBS increases in the mixture solution with the block copolymer. The surface parameters of adsorption and micellization for single and mixed solutions were investigated. The results show that the surface and micellization properties of SDBS were improved as a result of mixing with the block copolymer. The mole fractions in the micelles and interaction parameters of the mixed solutions were calculated. The foam stability of single and mixed solutions at 25 °C was determined. The results show that the SDBS has more foam stability than the block copolymer and the foam stability increases as the molar ratio of SDBS increase in mixed solution of it with block copolymer.

Physicochemical Studies on the Interfacial and Bulk Behaviors of Sodium N-Dodecanoyl Sarcosinate (SDDS)

Sodium N-dodecanoyl sarcosinate (SDDS), a novel amino-acid based surfactant, has immense biological and industrial importance. Although it is being used in a number of cosmetic formulations, systematic analysis of the bulk and interfacial properties of the surfactant is scarce in the literature. In this study, effects of salt, temperature, and pH on the self-association and related properties of SDDS have been examined in detail using methods such as tensiometry, conductometry, fluorimetry, pH-metry, spectrophotometry, calorimetry, and circular dichroism. The nature of amphiphilic packing and the aggregation numbers of the assemblies have been deciphered. Properties of the acid form of the surfactant have also been explored. The results have been conceptually rationalized and systematically presented together with associated energetics of the interfacial adsorption and self-aggregation of the surfactant in the bulk.

The Characteristic Curvature of Ionic Surfactants

Characterizing the hydrophilic-lipophilic nature of a surfactant molecule has been a challenge for colloid scientists and technologists. The hydrophilic-lipophilic balance (HLB), the packing factor, the phase inversion temperature (PIT) and the natural curvature of the surfactant are all terms that seek to address this issue. In this article we build on the hydrophilic–lipophilic difference concept (HLD) (Salager et al. Langmuir, 16, 5534–5539, 2000) to develop a methodology to determine a characteristic curvature (Cc) for ionic surfactants based on the phase behavior of mixed ionic surfactant microemulsions. In essence, the method consists of evaluating the shift in optimal electrolyte concentration as a function of the mole fraction of the test surfactant in a mixture with a reference surfactant, sodium dihexyl sulfosuccinate (SDHS) and applying the appropriate HLD equation for ionic surfactant mixtures to determine Cc. The values of Cc were determined for a range of surfactants, including sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), sodium naphthenate, and others. The method was also extrapolated to nonionic additives and hydrophilic linkers. It was observed that the calculated values of Cc were similar to those predicted by group contribution models, however the proposed method can be used even for complex surfactant mixtures. Finally, when Cc values were compared to apparent packing factor and HLB values, it was found that Cc is correlated with the apparent packing factor of ionic surfactants, and that Cc correlates with the HLB value for nonionic amphiphiles. The physical interpretation of Cc, and its potential application in the Net-Average Curvature equation of state for oil-surfactant-water systems is discussed.

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.

---

Environmentally Friendly Vegetable Oil Microemulsions Using Extended Surfactants and Linkers

Microemulsion formation of triglyceride oils at ambient conditions (temperature and pressure) and without the addition of co-oil and/or alcohols is challenging at best. Undesirable phases, such as macroemulsions, liquid crystals and sponge phases, are often encountered when formulating triglyceride microemulsions. The purpose of this study is to investigate the use of extended surfactants, lipophilic linkers, and hydrophilic linkers in enhancing triglyceride solubilization and interfacial tension reduction. We have studied two classes of extended surfactants, linear alkyl polypropoxylated sulfate (LAPS) surfactants and linear alkyl polypropoxylated ethoxylated sulfate (LAPES) surfactants. Linkers evaluated were oleyl alcohol (lipophilic linker), sodium mono and dimethyl naphthalene sulfonate (SMDNS), and polyglucoside (hydrophilic linkers). Oils studied include olive, peanut, soybean, canola and sunflower oils. The effect of electrolyte concentration on microemulsion phase behavior was studied. The microemulsion “fish” diagram was obtained by plotting the total surfactant and linker concentrations versus the electrolyte concentration. We were able to form Winsor Type I, II, III and IV microemulsions at ambient conditions and without co-oil or short and medium chain length alcohol addition. Winsor Type III and IV triglyceride microemulsions are particularly useful in numerous applications such as cosmetics, vegetable oil extraction and soil remediation.

A Rheological Approach to Viscoelastic Worm-Like Micelles of Tunable Properties

The rheological behavior of micellar solutions of cationic surfactant, cetyl trimethyl ammonium bromide in the presence of a salt (KBr) and a co-surfactant (n-octanol) were analyzed. Shear viscosity and shear moduli were measured as a function of concentrations of the co-surfactant and additive. When these concentrations attained a certain critical threshold value, the micellar solution was found to exhibit a nonlinear viscoelastic behavior. It is due to the formation of supramolecular structures, which has been described by the Maxwell model of a viscoelastic fluid typical of worm-like micelles. The rheological behavior was also analyzed using Carreau and Carreau–Gahleitner models which were found to be in good agreement with the experimental results.

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.

Comparison of Surface-Active Properties of (Alkyloxycarbonylmethyl)trimethylammonium Chlorides and Alkyltrimethylammonium Chlorides

Surface-active properties of cleavable surfactants with a betaine ester group—(n-alkyloxycarbonylmethyl)trimethylammonium chlorides, used as separation reagents—were investigated. Critical micelle concentrations, dispersing powers, and foaming powers were comparable to those of alkyltrimethylammonium chlorides with the same total number of carbon atoms. On the other hand, the solubilities of the four hydrophobic dyes N,N-dimethyl-3-nitroaniline, naphthalene, pyrene, and oil orange SS in the former surfactant solutions were equal to or slightly smaller than those in the solutions of the latter surfactants with the same alkyl chain length. The alkali hydrolysis yields of the formers approached 100% in aqueous buffer solution at pH 10 and 25 °C within 10 min, and the yield at pH 9 was dependent on the alkyl chain length. This type of surfactant was also found to be as an efficient separation reagent which disperses carbon black and solubilizes the above dyes into aqueous neutral solution and then separates them instantaneously and almost perfectly as precipitates when a small excess of NaOH is added.