Study of the Interaction Between Methyl Orange and Mono and Bis-Quaternary Ammonium Surfactants

The solubilization and interaction of an azo-dye (methyl orange) with dodecyl trimethyl ammonium bromide and cationic gemini surfactants in the series of alkanediyl α,ω-bis[(dimethyl alkyl ammonium)bromide)] referred to as (m-s-m), m = 10, 12, 14 and s = 2, 3, 4 were investigated by means of UV–Vis spectroscopy. Aggregation with the anionic dye was reflected by a hypsochromic shift with a decrease in the intensity of the absorption band. The results also show a bathochromic shift followed by a sharp increase in the intensity of the maximum absorption band λ_max after the critical micellar concentration (CMC). This indicates that the dye solubility increased with increasing surfactant concentration. It was also observed that the aggregation of surfactant and dye takes place at a surfactant concentration far below the CMC of the individual surfactant. The effects of the chain length as well as the spacer length of gemini surfactants on the critical aggregation concentration and CMC were also examined. Moreover, the partition coefficients between the bulk water and surfactant micelles K _S and K _X as well as the Gibbs energies of distribution of dye between the bulk water and surfactant micelles were determined using the pseudo-phase model. The effect of the hydrophobic chain length and spacer of gemini surfactants on the distribution parameters is also reported.     

Synthesis and some studies on fluorinated cationic surfactants: surface and biocidal activities

Three fluorinated cationic surfactants were prepared by condensing N-(2-bromoethyl)perfluoroalkylamides with stoichiometric amounts of pyridine, triethanolamine, and triethylamine to produce three quaternary ammonium salts. The surface and biocidal properties of these surfactants were investigated to find the relation between the structure of the hydrophilic portion of the compounds and their efficiency as biocides. The properties studied included critical micelle concentration (CMC), effectiveness (II_CMC), surface excess concentration (T_max), and area occupied by a molecule (A_min). Free energies of micellization (ΔG _mic ^o) and adsorption (ΔG _ads ^o) of the surfactants in aqueous solution were calculated. The minimal inhibitory concentrations of the prepared compounds were tested against five strains as representative group of microorganisms.     

Micellization Behavior of the 14-2-14 Gemini Surfactant with Some Conventional Surfactants at Different Temperatures

Mixed micellization behavior of the dimeric cationic surfactant ethanediyl-1,2-bis(dimethyl tetradecyl ammonium bromide) with monomeric cationic surfactants cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), tetradecyl dimethyl benzyl ammonium chloride (C14BCl) and cetyl dimethyl benzyl ammonium chloride (C16BCl) was studied in aqueous and aqueous polyethylene glycol (PEG) solutions at various temperatures (298.15, 308.15 and 318.15 K) using conductometric and viscometric methods. The behavior of these mixed systems was analyzed in light of Rubingh’s regular solution theory. The conductivity study indicates that the above systems behave nonideally with mutual synergism at 298.15 and 308.15 K, whereas antagonistic behavior is exhibited at 318.15 K. In the presence of PEG solution, various thermodynamic parameters associated with transfer of surfactant monomers from the medium consisting of polymer-free mixed micelles to polymer-bound mixed micelles like ∆G _t^o, ∆H _t^o and ∆S _t^o at various temperatures were evaluated and discussed. The viscosity study shows that in aqueous solutions all these combinations exhibit significant negative departure in the relative viscosity (η_r) from the additivity rule at 298.15 and 308.15 K, whereas at 318.15 K these combinations (except in the case of C14BCl) follow the additivity rule. In presence of 5% PEG solution, all the combinations show positive departure from the additivity rule except the combination with C14BCl which shows negative departure at all the studied temperatures.     

Effect of Polar Organic Solvents on Self‐Aggregation of Some Cationic Monomeric and Dimeric Surfactants

Surface and micellization behavior of some cationic monomeric surfactants, viz., cetyldiethylethanolammonium bromide (CDEEAB), cetyldimethylethanolammonium bromide (CDMEAB), tetradecyldiethylethanolammonium bromide (TDEEAB) and dimeric surfactants, i.e., alkanediyl‐α, ω‐bis(dimethylhexadecylammonium bromide) (C₁₆‐s‐C₁₆, 2Br^? where s = 4, 12), butanediyl‐1,4‐bis(dimethyldodecylammonium bromide (C₁₂‐4‐C₁₂, 2Br^?) and 2‐butanol‐1,4‐bis(dimethyldodecylammonium bromide) (C₁₂‐4(OH)‐C₁₂, 2Br^?), was studied in water‐organic solvents [10 and 20 % v/v ethylene glycol (EG) and diethylene glycol (DEG)] by conductivity, surface tension and steady‐state fluorescence methods at 300 K. The main focus of the present work is on the study of the effect of organic solvents on the critical micelle concentration (CMC), Gibbs free energy of micellization (ΔG°_m), Gibbs free energy of transfer (ΔG°_trans), Gibbs adsorption energy (ΔG°_ads) and some interfacial parameters such as the surface excess concentration (Γ_max), minimum area per surfactant molecule (A_min) and surface pressure (π_CMC). The aggregation number (N_agg) and Stern‐Volmer quenching constant (K_SV) were also determined by the steady‐state fluorescence method. It was observed that N_agg decreased with increasing volume percent of organic solvent. The results exhibited an increase in CMC in water‐organic solvents as compared to the respective surfactants in pure water. The negative values of ΔG°_m and ΔG°_ads indicate a spontaneous micellization process. The thermodynamics of micellization revealed that the micellization‐reducing efficiency of glycols increases with the concentration and the number of ethereal oxygens in the glycol.     

Aggregation and Thermodynamic Properties of Some Cationic Gemini Surfactants

In this study, the gemini surfactants of the alkanediyl-α-ω-bis(alkyl dimethyl ammonium) dibromide type, on the one hand, with different alkyl groups containing m carbon atoms and an ethanediyl spacer, referred to as “m-2-m” (m = 10, 12 and 16) and, on the other hand, with n-C₁₆ alkyl groups and different spacers containing s carbon atoms, referred to as “16-s-16” (s = 2, 6, 10 and Ar (8)) have been synthesized, purified and characterized. The critical micelle concentration (CMC), micelle ionization degree (α) and Gibbs free energy of micellization (∆G _mic) of these surfactants and the monomeric cationic surfactants DTAB and CTAB have been determined by means of electric conductivity measurements. In addition, the temperature dependence of the CMC was determined for the 10-2-10 gemini surfactant. The CMCs of the gemini surfactants are found to be much lower than those of the corresponding monomeric surfactants and the effect of the hydrophobic alkyl chain length is more important than that of the spacer. The CMC of 16-s-16 passes through a maximum of (or around) s = 6 and then decreases for s = 10. The presence of a maximum CMC is explained by the contribution of a change of conformation of the surfactant with increasing spacer chain length. The changes of α with s and m are found qualitatively similar to those found for CMC values. The values of ∆G _mic are more negative for the dimers than for the monomers and also change with an increasing spacer carbon number, as CMC values do. The thermodynamic parameters of micellization indicate that the micellization of 10-2-10 is enthalpy driven.     

Synthesis and Self-Aggregation of a Hydroxyl-Functionalized Imidazolium-Based Ionic Liquid Surfactant in Aqueous Solution

This paper deals with the synthesis and self-aggregation of a hydroxyl-functionalized imidazolium-based ionic liquid (IL) surfactant, namely 1-hydroxyethyl-3-dodecylimidazolium chloride ([C₂OHC₁₂im]Cl). The molecular structure was confirmed by means of electrospray ionization mass spectrometry (ESI–MS), ¹H nuclear magnetic resonance (¹H NMR) and elemental analysis. Many important physicochemical parameters, such as the critical micelle concentration (CMC), the surface tension at CMC (γ_CMC), the adsorption efficiency (pC ₂₀), the surface pressure at CMC (Π_CMC), the maximum surface excess (Γ _m ), the minimum molecular cross-sectional area (A _min), the value of CMC/C ₂₀, the average number of aggregation (N _m ) and the micellar microenvironment polarity were determined by surface tension-concentration curves, fluorescence spectra, and electrical conductivity. The phenomena of the second CMC, the concentration dependence of N _m , and the critical average aggregation number (N _m,c) of imidazolium-based IL surfactants are reported for the first time in this paper.     

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.     

Mixed Micellization of Cationic Gemini Surfactants with Primary Linear Alkylamines

Due to the potential use of amines as co-surfactants in microemulsions, the effect of adding alkylamines (C₄–C₈NH₂) on the aggregation properties of cationic gemini surfactants [pentanediyl-1, 5-bis(dimethylcetylammonium bromide) and hexanediyl-1, 6-bis(dimethylcetylammonium bromide), referred to as 16-5-16 and 16-6-16 compounds] has been studied using tensiometry at 303 K. Data on critical micelle concentration (CMC), the surface properties C₂₀ (the surfactant concentration required to reduce the surface tension by 20 mN/m), Г_max (maximum surface excess), A _min (minimum surface area per molecule) evaluated from the surface tension versus surfactant concentration plot, the interaction parameters β^σ (for mixed monolayer formation at the aqueous solution/air interface), and β^m (for mixed micelle formation in aqueous medium) are reported. A synergistic interaction was observed both in the micelle as well as at interface, as evident from interaction parameters. Theoretical models of Clint, Rubingh and Rosen were used to explain and compare the results. More synergistic interaction was observed in 16-5-16 as compared to 16-6-16. The CMC values of 16-s-16 (s = 5, 6) decreased with increasing amine concentrations and the extent of the effect followed the sequence: octylamine > heptylamine > hexylamine > pentylamine > butylamine.     

Undecanoic and 10-Undecenoic Acid-Based Amidobetaines and Amidoamine Oxides

Three types of undecanoic and 10-undecenoic acid-based surfactants were synthesized in the present work: amphoteric amidobetaines, cationic amidobetaine chlorides and nonionic amidoamine oxides. Structural characterizations of synthesized compounds were based on nuclear magnetic resonance (NMR) (¹H and ¹³C) and mass spectrometry. Surface properties, such as critical micelle concentration (CMC), surface tension at cmc (γ _cmc), efficiency of surface adsorption (pC20), surface excess (Γ_max) and minimum area per molecule (A _min) at the air–water interface, were determined by surface tension methods. Fluorescence probing techniques were also employed for the measurement of CMC, as well as steady state anisotropy (r) at the micellar core. The CMC of the studied surfactants follow the order: amidobetaine > amidobetaine chloride > amidoamine oxide. The influence of the terminal double bond in the hydrophobic alkyl chain on CMC was also assessed, and a significant increase in CMC was found due to the introduction of the double bond in the cases of amidobetaine chlorides and amidoamine oxides. These two types of surfactants showed higher rigidity at the micellar core compared to their corresponding unsaturated counterparts. However, such influence of unsaturation on the hydrophobic moiety was not observed in the case of amidobetaines. In all three types of surfactants, the saturated surfactant exhibited a lower γ _cmc and A _min, but higher Γ_max, r and pC20 compared to its unsaturated counterpart.     

Synthesis and Some Properties of Fluorinated Cationic Surfactants

Three fluorinated cationic surfactants were prepared by condensing N-methyl diethanol amine pentafluoro benzoate with stoichiometric amounts of octyl, dodecyl or hexadecyl bromide. The surface properties and parameters were investigated to find the relationship between the structures of the hydrophobic portion of such compounds. The properties studied include surface tension, critical micelle concentration (CMC), effectiveness (Π_cmc), maximum surface excess (Γ_max) and minimum surface area (A_min) were investigated with respect to different concentrations at 25 °C. Standard free energies of micellization and adsorption of the prepared surfactants in the aqueous solution were studied. The values of Γ_max, standard free energies of micellization \Updelta \textG_\textmic^\texto \Updelta {\text{G}}_{\text{mic}}^{\text{o}} and adsorption \Updelta \textG_\textads^\texto \Updelta {\text{G}}_{\text{ads}}^{\text{o}} were found to increase with the chain length, while the cmc and minimum surface area occupied by one molecule A_min were found to decrease. The biocidal activity was determined through the inhibition zone diameter of prepared compounds which were measured against five strains of a representative group of microorganisms.     

Micellization Behavior of Cationic Gemini Surfactants in Aqueous-Ethylene Glycol Solution

The micellization behavior of gemini surfactants i.e. alkanediyl-α,ω-bis(cetyldimethylammonium bromide) (C₁₆-s-C₁₆,2Br⁻ where s = 3, 4, 10) in 10% (v/v) ethylene glycol solution was investigated by surface tension and conductometric measurements at 300 K. The critical micelle concentration, degree of micellar ionization, surface excess concentration, minimum surface area per molecule of surfactant, surface pressure at the CMC and Gibbs energy of adsorption of the dimeric surfactants have also been determined in the presence of different salts (NaCl, NaBr and NaI). The critical micelle concentration and degree of micellar ionization values decrease significantly in the presence of sodium halides and follows the sequence NaCl < NaBr < NaI. The free energy, enthalpy and entropy of micellization of dimeric surfactants in 10% (v/v) ethylene glycol solution were determined using the temperature dependence of the critical micelle concentration. The standard free energy of micellization was found to be negative in all the cases.     

Synthesis and Investigation of Surface Active Properties of Counterion Coupled Gemini Surfactants

Three counterion coupled gemini (cocogem) surfactants in the series 1,6‐bis(N,N‐alkyldimethylammonium) adipate, referred as n‐6‐n (n = 12, 14, 16), were synthesized, purified and characterized by ¹H NMR and ¹³C NMR. Their physicochemical properties were investigated by electrical conductivity and surface tension measurements. The degree of ionization, critical micelle concentration (CMC), surface excess at the air/solution interface (Γ_max), minimum area per surfactant molecule at the air/solution interface (A_min), surface tension at the CMC (γ_CMC), and pC₂₀ (negative log of the surfactant molar concentration, required to reduce the surface tension of water by 20 mN m^?1) were calculated. Increase in tail length of the surfactants increases the efficiency of surfactants to decrease the surface tension of water. Thermodynamic parameters, viz. molar free energy at the maximum adsorption attained at CMC (G_min), standard Gibb's energy of micellization (), and standard Gibbs energy of adsorption (), were also calculated. The and values show that the monomers were preferred to be adsorbed at the air/water interface and then in the micellar formation in the bulk. Additionally, fluorescence measurements were used to find the aggregation number. Other relevant surface properties (Krafft point, emulsion stability, foaming ability, micellar stability and dye solubilization ability) were also evaluated. These results suggest that with respect to emulsion formation, micellar stability and dye solubilization, the cocogem with a 16‐carbon chain gives better results, producing 89 % more stable foams and shows better aggregational behavior.     

Preparation,surface-active properties,and antimicrobial activities of bis-quaternary ammonium salts from amines and epichlorohydrin

A series of new cationic surfactants, bis-quaternary ammonium salts, were prepared from tert-alkylamine and a product of the reaction of epichlorohydrin with decyl- and dodecylamine, and their surface-active properties were measured. Specifically, the critical micelle concentration (CMC), effectiveness of surface tension reduction (γ_CMC), surface excess concentration (Γ), area per molecule at the interface (A), and standard free energies of adsorption (ΔG _ads ^o) and of micellization (ΔG _mic ^o) were determined. All these surfactants showed good water solubility and low CMC, more than one order of magnitude lower than those of corresponding mono-alkylammonium salts. They also showed good foaming properties but worse wetting capabilities. Many of these compounds had antimicrobial activities against gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis) and yeast (Candida albicans), but they were not active against molds.     

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.     

Ferrocene-Based Cationic Surfactants: Surface and Antimicrobial Properties

A novel series of ferrocenyl surfactants was synthesized by the reaction of ferrocene disulfonic acid with different primary and tertiary fatty amines to produce the corresponding ammonium salts Fc[SO₃ ^{− +}NH₃(CH₂) _n CH₃]₂, where n = 9, 11, or 15 and Fc[SO₃^{− +}NH(CH₃)₂(CH₂) _n CH₃]₂, where n = 7 or 11, respectively, and where Fc = ferrocene. Chemical structures were confirmed by microelemental analysis, FTIR, and ¹H NMR spectroscopy. The critical micelle concentration of each prepared surfactant was determined using equilibrium surface tension. Furthermore, air/water interface parameters including effectiveness (π _CMC), efficiency (Pc₂₀), maximum surface excess (Г_max), and minimum surface area (A _min) were determined at 30, 40, and 50 °C. Thermodynamic parameters (ΔG°, ΔS°, and ΔH°) for both micellization and adsorption processes were recorded. The new synthesized surfactants were screened as antimicrobial agents against different bacterial and fungal organisms.     

Synthesis and Surface Properties of Polyether-Based Silicone Surfactants with Different Siloxane Groups

A series of polyether-based silicone surfactants with different hydrophobic chains (trimethylsiloxy, triethylsiloxy, and triisopropylsiloxy) were synthesized. The molecular structures were confirmed using ¹H nuclear magnetic resonance (NMR), ¹³C NMR, ²⁹Si NMR, and fourier transform infrared spectroscopy (FT-IR). The effect of the siloxane groups on the physicochemical properties, surface tension (γ), critical micelle concentration (CMC), surface tension at the CMC (γ_CMC ), adsorption efficiency (pC₂₀), surface pressure at the CMC (π_CMC ), maximum surface excess (Γ_max ), single silicone surfactant molecule at the air/water interface (A_min ), and the standard free energy of adsorption (), of the polyether-based silicone surfactants was investigated. Results indicate that the polyether-based silicone surfactants can reduce the surface tension of water to approximately 25–31 mN m⁻¹ and the surface activity of silicone surfactants is enhanced with increasing branched trimethylsiloxyl and sterically hindered siloxane groups.     

Surface Properties and Thermodynamic Parameters of Some Sugar-Based Ethoxylated Amine Surfactants: 1—Synthesis,Characterization, and Demulsification Efficiency

Several ethoxylated sugar-based amine surfactants have been synthesized and characterized by IR and ¹HNMR spectroscopy. The surface activity of the prepared compounds has been thoroughly studied and some of their surface properties (such as CMC, Γ_max, and A _min) have been calculated. The surface properties of the prepared compounds were correlated to their chemical structure. It was found that CMC decreases when increasing the molecular weight of polyethylene glycols, whereas A _min increases. Furthermore, the thermodynamic parameters of adsorption and micellization were also calculated. They include ΔG, ΔH, and ΔS of micellization and adsorption. The data show that the synthesized surfactants favor adsorption, so that they can be used as demulsifiers for crude oil emulsions. In this respect, the demulsification test was carried out and the results of demulsification efficiency were correlated to the chemical composition of the investigated compounds. Some factors that affect the demulsification efficiency were also considered.     

Preparation and Application of Fluorinated Cationic Surfactants

Four fluorinated cationic surfactants were prepared by condensing 2,2,3,3, tetrafluoro-1-propyl chloroacetate with stoichiometric amounts of pyridine, 2-hydroxypyridine, 8-hydroxyquinoline and 8-hydroxyquinaldine to produce four quaternary ammonium salts. The surface and biocidal properties of these surfactants were investigated. Surface properties of their solutions including surface tension, critical micelle concentration (CMC), effectiveness (Π_cmc), maximum surface excess (Γ_max) and minimum surface area (A _min) were investigated with respect to different concentrations at 25 °C. Standard free energies of micellization and adsorption of the prepared surfactants in the aqueous solution were studied. The biocidal activity was determined via the inhibition zone diameter of prepared compounds which tested against six strains as a representative group of microorganisms.

Surface properties of N-alkanoyl-N-methyl glucamines and related materials

The surface properties [effectiveness of surface tension reduction (γ_CMC) critical micelle concentration (CMC), efficiency of surface tension reduction (pC ₂₀), maximal surface excess concentration (Γ_max), minimal area/molecule at the interface (A _min), and the (CMC/C ₂₀) ratio] of some well-purified N-alkanoyl-N-methyl glucamines and related polyol-based N-methyl amide-type surfactants, having the structural formula RC(O)N(Me)CH₂(CHOH)_xCH₂OH, where RC(O)=undecanoyl, lauroyl, tridecanoyl, myristoyl, and x=1,3, and 4, were investigated at 25°C in distilled water and 0.1 M NaCl. Water solubility of these compounds does not simply depend on the number of hydroxyl groups in the molecule but is associated with the balance between intermolecular hydrogen bonds and hydrogen bonds formed with water molecules. The fundamental interfacial properties, such as CMC and γ_CMC and two thermodynamic parameters, standard free energy of adsorption and standard free energy of micellization, were found to be significantly dependent on the hydrophobic acyl chain rather than on the number of CHOH groups in the hydrophilic moieties. By contrast, the practical performance properties were greatly dependent on the nature of the hydrophilic group. As a whole, these surfactants had desirable foaming properties and efficient wetting abilities. Furthermore, synergism in foaming and wetting abilities was observed in a binary mixture of these surfactants with an alkyloxyethylene sulfate.     

Counterion-coupled gemini (Cocogem) surfactants based on dodecylisopropylol amine and dicarboxylic acids: synthesis,characterization and evaluation as biocide against SRB

New cocogem surfactants were synthesized by interaction of dodecylisopropylol amine with dicarboxylic (oxalic, succinic, adipic, sebacic, tartaric, maleic, fumaric, isophthalic) acids. By tensiometric method, the surface activity of aqueous solutions of the synthesized cocogem surfactants at the border with air was studied and, by conductometric method, the specific electrical conductivity of these solutions was determined. The degree of counterion binding (β), critical micelle concentration (CMC), effectiveness of surface tension reduction (π_CMC), surface excess concentration (Γ_max), area per molecule at the interface (A_min), changes of Gibbs free energies of adsorption (ΔG_ad) and micellization (ΔG_mic) have been calculated. The character of change of the colloidal-chemical indices depending on spacer-group nature and length has been clarified. So, with an elongation of the spacer group and when passing from cis-form to trans-form, the value of CMC decreases. The obtained cocogem surfactants exhibit a considerable bactericidal effectiveness against sulfate-reducing bacteria. The bactericide properties of the cocogem surfactants containing in the spacer chain a saturated hydrocarbon fragment and benzene ring are stronger than for the others.