Surface Activity Properties and Aggregation Behaviors of Partially Fluorinated Gemini Surfactants in Aqueous Solution

The surface activity and aggregation behavior of partially fluorinated gemini surfactant N,N′‐bis(3‐perfluorohexyl‐2‐hydroxypropyl)‐N,N′‐dipropanesulfonylhexylenediamine (N‐6‐Sul) was studied by surface tension, resonance light scattering and fluorescence spectra measurements. The critical micelle concentration (CMC) values obtained by the three methods are in good agreement. The surface activity parameters such as the effectiveness of surface tension reduction (Π_cmc), the maximum surface excess concentration (Γ_max) and the minimum surface area per molecule (A_min) were obtained through surface tension curves. The effects of pH, inorganic salts and temperature on the surface activity were also investigated. The morphology and size of the aggregates of N‐6‐Sul were examined by transmission electron microscopy (TEM). The results show that the partially fluorinated gemini surfactant N‐6‐Sul has many advantages such as high surface activity, low CMC value, great salt tolerance and temperature resistance.     

Synthesis and Performance Evaluation of CO2/N2 Switchable Tertiary Amine Gemini Surfactant

A type of switchable tertiary amine Gemini surfactant, N,N′‐di(N,N‐dimethyl propylamine)‐N,N′‐didodecyl ethylenediamine, was synthesized by two substitution reactions with 3‐chloro‐1‐(N,N‐dimethyl) propylamine, bromododecane and ethylene diamine as main raw materials. The structure of the product was characterized by FTIR and ¹H‐NMR. We also investigated the surface tension when CO₂ was bubbled in different concentrations of surfactant solution and the influence of different CO₂ volumes on surface tension under a constant surfactant concentration. Finally the surface tension curve and the related parameters were acquired by surface tension measurements. The experimental results showed that the structure of the synthesized compounds were in conformity with the expected structure of the surfactant, and displayed a better surface activity after bubbling CO₂. The critical micelle concentration (CMC) surface tension at CMC (γ_cmc) pC₂₀ (negative logarithm of the surfactant's molar concentration C₂₀, required to reduce the surface tension by 20 mN/m) surface excess (Γ_max) at air/solution interface and the minimum area per surfactant molecule at the air/solution interface (A_min) were determined. Results indicate that the target product had good surface activity after bubbling CO₂.     

Surface and Aggregation Properties of Synthesized Cetyl Alcohol Based Bis-Sulfosuccinate Gemini Surfactants in Aqueous Solution

A series of cetyl alcohol based anionic bis‐sulfosuccinate gemini surfactants (BSGSCA1,4; BSGSCA1,6 and BSGSCA1,8) with different spacer lengths was prepared using dibromoalkanes. The surfactant structure was elucidated using elemental analysis, Fourier transform infrared spectroscopy (FT‐IR) and nuclear magnetic resonance spectroscopy (NMR). Surface tension measurements were used to determine the critical micelle concentration (CMC), the surface tension at the CMC (γ_CMC), surface pressure at the CMC (π_CMC) and efficiency of adsorption (pC20). On the basis of surface studies, the CMC and γ_CMC decreases with increasing length of the spacer group. The micelle aggregation number, determined by fluorescence quenching studies, increases with increasing surfactant concentration above the CMC. The micropolarity in the micelle increases with increasing length of the spacer and decreases with increasing surfactant concentration.     

Salt Effect on the Solution Properties of Cationic Gemini/Conventional Surfactants in the Presence of the Nonionic Polymer Hydroxypropylmethyl Cellulose

In this article, we report the salt effect on interaction of a water-soluble polymer hydroxypropylmethyl cellulose (HPMC) with the cationic Gemini surfactant (ethane-1, 2-diyl bis(N,N-dimethyl-N-hexadecylammoniumacetoxy) dichloride, 16-E2-16), and also its monomeric counterpart cetyltrimethylammonium chloride (CTAC) using the tensiometric method. Surface tension of the amphiphiles diminished in the presence of the polymer as well as salts; eventually, the polymer gets saturated with the surfactant and there is no further change of surface tension of the solution. Interaction between the polymer and surfactant starts at the critical aggregation concentration (CAC) that is stronger for 16-E2-16 than CTAC. CAC and critical micelle concentration (CMC) values of the surfactant-polymer binary mixtures at various concentrations of the polymer were determined. CAC as well as CMC of 16-E2-16 are considerably lower than CTAC. The inorganic salts (KCl and KBr) have a considerable influence on the polymer–surfactant interaction.     

Surface Activity and Performance Properties of Gemini Salts of Linear Alkylbenzene Sulfonate in Aqueous Solution

Gemini salts of linear alkylbenzene sulfonate (LABS) were prepared by neutralization of sulfonic acid with a series of low-molecular-weight diamines in aqueous solution. The equilibrium surface activity of Gemini salts of LABS was determined by measuring the surface tension as a function of surfactant concentration to determine the critical micelle concentration (CMC), surface tension at the CMC (γ_CMC), and the area per molecule at the air-water interface (Ų). Electrical conductivity was measured as a function of surfactant concentration to determine the CMC and counterion binding. Dynamic surface tension was measured using a bubble pressure tensiometer to infer the rate at which the surfactant migrates to the air-water interface. Equilibrium interfacial tension against mineral oil was measured using a spinning drop tensiometer. Dynamic interfacial tension was measured using a drop volume tensiometer. The surface tension, CMC, and interfacial tension of Gemini salts of LABS decreased compared to monovalent organic and inorganic salts. The CMC decreases with increasing molecular weight of the diamine spacer group. Dynamic surface and interfacial tension of Gemini salts of LABS are lower than monovalent salts. The foam volume of Gemini salts of LABS was determined using a high shear blender test. The foam volume of Gemini salts of LABS is lower than monovalent salts and depends on the size of the spacer group. Hard-surface cleaning was measured using artificial soil applied to white Formica tiles. Soil removal was determined by optical reflectance as a function of abrasion cycles. Gemini salts of LABS show reduced hard-surface cleaning performance compared to monovalent salts. Detergency of different types of soils on cotton and polyester/cotton fabric was determined by optical reflectance measurements. Gemini salts of LABS show improved cleaning performance compared to monovalent salts. Cleaning performance increases with increasing molecular weight of the diamine spacer group. In situ neutralization of LABS with organic diamines is a simple and efficient way to prepare anionic Gemini surfactants for industrial scale applications.     

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,characterization, and surface properties of phenylalanine-glycerol ether surfactants

A novel homologous series of 1-N-l-phenylalanine-glycerol ether surfactants was synthesized in satisfactory yields via reaction of epichlorohydrin with aliphatic alcohols with alkyl chains of 10–15 carbon atoms. Structural assignment of the new compounds was made on the basis of elemental analysis and spectroscopic data. 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 (pC₂₀), and the interfacial area occupied by the surfactant molecules (A_min) were determined from aqueous surface tension measurements using the Wilhelmy plate technique.     

Influence of Spacer Nature on the Aggregation Properties of Anionic Gemini Surfactants in Aqueous Solutions

A series of anionic gemini surfactants with the same structure except the spacer nature have been studied. Their solution properties were characterized by the equilibrium surface tension and intrinsic fluorescence quenching method. The critical micelle concentrations (CMC), surface tension at cmc, C₂₀, and the micelle aggregation number (N) were obtained. The surface tension measurements indicate that these gemini surfactants have much lower cmc values and great efficiency in lowering the surface tension of water compared with those of conventional monomeric surfactants. Furthermore, the standard free energy of micellization for anionic gemini surfactants was also determined. The results showed that the nature of the spacer has an important effect on the aggregation properties of gemini surfactants in aqueous solutions. The surfactant with a hydrophilic, flexible spacer was more readily able to form micelle compared with the surfactant with a hydrophobic, rigid spacer, which leads to a lower CMC value, larger N, more negative free energy of micellization, and a more closely packed micelle structure.     

Polymeric surfactants for enhanced oil recovery. Part I—critical micelle concentration of some ethoxylated alkylphenol—formaldehyde nonionics

Four low molecular weight nonionic polymeric surfactants were prepared by condensing octyl-, dodecyl-, tetradecyl- and hexadecylphenol with para-formaldehyde, and then reacting the resulting resins with ethylene oxide to obtain products with the desired degree of ethoxylation. The molecular weights of the prepared alkylphenol-formaldehyde resins (prior to ethoxylation) were determined by vapour pressure osmometry. The surface tensions of aqueous solutions of these nonionic polymeric surfactants were determined by using the spinning drop method. Plotting the surface tensions obtained versus the logarithm of concentrations resulted in two lines: the pre-CMC (CMC = critical micelle concentration) line (the linear portion below the CMC value) and the post-CMC line (the linear portion above the CMC value). Least squares regression analysis was performed to get the best equation for each of the two lines. Solving these two equations simultaneously resulted in the value of the CMC and the corresponding surface tension (γ_CMC) for each surfactant of the four polymeric nonionic groups. The CMC values obtained for these polymeric surfactants are of the same order of magnitude obtained for monomeric and other polymeric nonionic surfactants.     

Synthesis,Characterization and Surface Activity of Hexadecyl <Emphasis Type="Italic">o</Emphasis>-Xylene Sulfonate Isomers

This paper deals with the synthesis of a series of hexadecyl o-xylene sulfonate isomers (with the o-xylene ring located at different positions along the n-hexadecyl chain) by a Friedel–Crafts reaction, and the Grignard reaction followed by a hydrogenation. The structure was confirmed by ¹H NMR. All analytical methods indicated high levels of purities of the isomers with the orthoxylene ring located at the first, third, fifth and seventh carbon atom on the n-hexadecane chain. The critical micelle concentration (CMC), surface tension and maximum surface excess concentration at CMC and area per molecule at the interface were determined. As the o-xylene sulfonate group is shifted toward the center of the hexadecyl chain, the branching degree is enhanced and the surfactant molecule tends to produce a much looser packing at the gas–liquid interface. Accordingly, at CMC, the adsorption density decreases, the CMC increases and the tension reduction is weakened.     

On the measurement of critical micelle concentrations of pure and technical-grade nonionic surfactants

The critical micelle concentrations (CMC) of nine commercial nonionic surfactants (Tween 20, 22, 40, 60, and 80; Triton X-100; Brij 35, 58, and 78) and two pure nonionics [C₁₂(EO)₅ and C₁₂(EO)₈] were determined by surface tension and dye micellization methods. Commercially available nonionic surfactants (technical grade) usually contain impurities and have a broad molecular weight distribution owing to the degree of ethoxylation. It was shown that the surface tension method (Wilhelmy plate) is very sensitive to the presence of impurities. Much lower CMC values were obtained with the surface tension method than with the dye micellization method (up to 6.5 times for Tween 22). In the presence of highly surfaceactive impurities, the air/liquid interface is already saturated at concentrations well below the true CMC, leading to a wrong interpretation of the break in the curve of surface tension (γ) vs. concentration of nonionic surfactant (log C). The actual onset of micellization happens at higher concentrations, as measured by the dye micellization method. Furthermore, it was shown that when a commercial surfactant sample (Tween 20) is subjected to foam fractionation, thereby removing species with higher surface activity, the sample yields almost the same CMC values as measured by surface tension and dye micellization methods. It was found that for monodisperse pure nonionic surfactants, both CMC determination methods yield the same results. Therefore, this study indicates that precaution should be taken when determining the CMC of commercial nonionic surfactants by the surface tension method, as it indicates the surface concentration of all surface-active species at the surface only, whereas the dye method indicates the presence of micelles in the bulk solution.     

Structural and Physicochemical Properties of a Polymerizable Surfactant Synthesized from <Emphasis Type="Italic">N</Emphasis>-Methylol Acrylamide

A new polymerizable nonionic surfactant with reactive vinyl groups has been synthesized from N‐methylol acrylamide using a two‐step procedure. The structure of the surfactant molecule was characterized by Fourier transform infrared, ¹H nuclear magnetic resonance and mass spectroscopy. The surface active properties alongside its self‐assembly properties were investigated by surface tension, electrical conductivity, and fluorescence spectroscopy measurements. As compared with other nonionic surfactants, this study showed that this polymerizable surfactant possesses slightly a higher critical micelle concentration (CMC) value and the surface tension value at CMC. The obtained CMC values were compatible among measurements, ca. 0.02–0.038 M. The evidence of micelle formation also provided by the zeta potential measurements and the obtained zeta potential values showed that the polymerizable surfactant solutions had limited stability. The hydrolysis stability and solubility of the polymerizable surfactant were also investigated. The solubility results have shown that it was soluble in polar solvents while insoluble in nonpolar solvents both at room temperature and 40 °C. The acidic and basic hydrolysis of the surfactant increased as the temperature increased and the hydrolysis stability was 180 min (basic medium) and 55 min (acidic medium) at 80 °C.     

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.     

Surface and thermodynamic parameters of sodium N-acyl sarcosinate surfactant solutions

Surface tension as a function of concentration and temperature was measured for solutions of N-acyl sarcosinates, RCON(CH₃)CH₂COONa. From the intersection points in the (γ-log c) curves, the critical micelle concentration (CMC) was determined at 20, 35, 50, and 65°C. Structural effects on the CMC, maximum surface excess, and the minimum area per molecule at the aqueous solution/air interface are discussed. The free energy, enthalpy, and entropy of micellization and adsorption of surfactant solutions also were investigated.     

Investigation of Mixing Behavior of both a Conventional Surfactant and Different Inorganic Salts with a Cationic Gemini Surfactant in Aqueous Solution

N,N′-bis [3-(dodecanoylamino)propyl]-N,N,N′,N′-tetramethylhexane-1,6-diaminium dibromide is a cationic Gemini surfactant including quaternary ammonium salt with amide groups. Critical micelle concentration (CMC) and some thermodynamic parameters of the cationic Gemini surfactant were investigated using surface tension and conductivity methods. Mixed micellization of binary mixtures of the cationic Gemini surfactant with a conventional surfactant cetyl trimethylammonium bromide (CTAB) was investigated using the conductometric method at five different temperatures ranging from 303.15 to 323.15 K. CMC, micellar ionization degree (α_m), counterion binding constant (g₁), interaction parameter (β), and activity coefficients ( and ) of mixed systems were found out from data of conductivity at different mole fractions for all studied temperatures. Additionally, the effects of some inorganic salts with different concentrations on the surface properties of cationic Gemini surfactant were examined by surface tension measurements. Some surface properties of the pure cationic Gemini surfactant and mixed salts systems were calculated using the data of surface tension.     

Synthesis and Physico-Chemical Properties of Sodium 3-Oxo-2-(3-(4-sulphonatophenyl)triaz-2-enyl)octadecanoate Anionic Surfactant

The novel anionic surfactant sodium 3‐oxo‐2‐(3‐(4‐sulphonatophenyl)triaz‐2‐enyl)octadecanoate (SSTO) was prepared from renewable raw materials; glycine and palmitic acid. Surface and bulk properties of SSTO were investigated by surface tension and electrical conductivity techniques at 298, 308, 318 and 328 K. Surface properties including critical micelle concentration (CMC), maximum surface excess concentration (Γ_max), minimum area per molecule (A_min), surface tension at CMC (γ_CMC), effectiveness of surface tension reduction (Π_CMC), efficiency of surface adsorption (pC₂₀), and degree of counterion dissociation (α) were determined. The thermodynamic parameters of micellization (ΔG°_mic, ΔH°_mic and ΔS°_mic) and adsorption (ΔG°_ad, ΔH°_ad and ΔS°_ad) were also investigated at 298, 308, 318 and 328 K. The effect of 3 wt% n‐propanol, n‐butanol and n‐pentanol on surface tension and conductivity at 298 K was also determined.     

Synthesis, Characterization and Surface Activity of Alkyl m-Xylene Sulfonate Isomers

This paper deals with the synthesis of a series of alkyl m-xylene sulfonate isomers (with the m-xylene located at the eighth carbon atom along the long alkyl chain) by the Friedel?CCrafts reaction, and the Grignard reaction followed by hydrogenation. The structures were confirmed by ¹H NMR. All analytical methods indicated high levels of purity of the isomers with the eighth carbon atom at the long alkyl chain. The critical micelle concentration (CMC), surface tension and maximum surface excess concentration at the CMC and area per molecule at the interface were determined. As the long alkyl chains increased the surfactant molecule tends to pack closely at the gas?Cliquid interface. Accordingly, the CMC decreased, the adsorption density increased, and the surface tension reduction was strengthened.     

Synthesis and surface activity of poly(maleic diester) surfactants

A series of maleic diester monomers have been prepared by esterification of maleic anhydride with a series of n-alkanols and poly(ethylene glycol) with different molecular weights. These monomers were polymerized in acetic anhydride solution in the presence of cumene hydroperoxide as initiator. The synthesized polymers have been characterized by IR and ¹H NMR spectroscopy, and their surface and thermodynamic properties as non-ionic surfactants is investigated. The surface tension as a function of concentration of the surfactant in aqueous solutions was measured at 298, 308, 318 and 328 K. The surface parameters are calculated. The data reveal that the CMC value of the polymeric surfactant is lower than that of the monomeric surfactant. It is also found that the CMC value decreases with increasing temperature and the number of ethylene oxide units in the surfactant molecule. The thermodynamic parameters of micellization and adsorption are also determined. The structural effectiveness of surface tension is discussed in terms of these parameters. © 1999 Society of Chemical Industry     

A Novel Zwitterionic Imidazolium-Based Ionic Liquid Surfactant: 1-Carboxymethyl-3-Dodecylimidazolium Inner Salt

A novel zwitterionic imidazolium-based ionic liquid (IL) surfactant, 1-carboxymethyl-3-dodecylimidazolium inner salt, was synthesized. The molecule structure was confirmed by means of electrospray ionization mass spectrometry, ¹H nuclear magnetic resonance and elemental analysis. The isoelectric point (pI) is 3.8 ± 0.1 at 35 ± 0.1 °C. The other 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 and the average number of aggregation (N _m) were determined by surface tension and steady-state fluorescence probe methods, respectively.     

Contact angle of surfactant solutions on precipitated surfactant surfaces. III. Effects of subsaturated anionic and nonionic surfactants and NaCl

The contact angles of saturated calcium dodecanoate (CaC₁₂) solutions containing a second subsaturated surfactant on a precipitated CaC₁₂ surface were measured by using the drop shape analysis technique. The subsaturated surfactants used were anionic sodium dodecylsulfate (NaDS), anionic sodium octanoate (NaC₈), and nonionic nonylphenol polyethoxylate (NPE). Comparing at the critical micelle concentration (CMC) for each surfactant, NaC₈ was the best wetting agent, followed by NaDS, with NPE as the poorest wetter (contact angles of 32⁰, 42⁰, and 62⁰, respectively). Surface tension at the CMC increased in the order NaC₈<NPE<NaDS, and subsaturated surfactant adsorption increased in the order NPE≪NaDS (1.4 vs. 84 μmole/g); adsorption of the NaC₈ was not measurable. Interfacial tension (IFT) reduction at the solid-liquid interface due to subsaturated surfactant adsorption is an important contribution to contact angle reduction, in addition to surface tension reduction at the air-water interface. Surfactant adsorption onto the soap scum solid is crucial to solid-liquid IFT reduction and to good wetting. The fatty acid was the best wetting agent of the three surfactants studied, probably because calcium bridging with the carboxylate group synergizes surfactant adsorption onto the solid of the higher molecular weight soap. NaCl added to NaDS surfactant results in depressed CMC, lower surface tension at the CMC, decreased NaDS adsorption onto the solid, and decreased reduction in solid-liquid IFT. The contact angle is not dependent on the NaCl concentration for NaDS. The NaCl causes an increased tendency to form monolayers, which decrease air-water surface tension, but a decreased tendency to form adsorbed aggregates on the solid; the two trends offset each other, so wettability is not affected by added salt. The Zisman equation does not describe the wetting data for these systems well except for NaDS, further emphasizing the danger of ignoring solid-liquid IFT reduction in interpreting wetting data in these systems.