Synthesis and Properties of Dissymmetric Gemini Surfactants

A series of novel dissymmetric gemini cationics surfactants was synthesized by three-step reactions. The dissymmetric gemini surfactants contain a dodecanoic acid dimethylethylamine ester as the constant cationic part on one side of the hydroxypropyl center and a similar other cationic part, but with a different acid length (from octanoic to palmitic), on the other side. The critical micelle concentration (CMC) and the effectiveness of surface tension reduction (γ _CMC) were determined. The surface tension measurements of dissymmetric gemini surfactants showed good water solubility, and low CMC had great efficiency in lowering the surface tension and a strong adsorption at the air/water interface. The CMC was observed to increase initially with the increase of the ester bond alkyl group. They also showed good foaming properties and wetting capabilites.     

Synthesis,Surface and Antimicrobial Activities of Novel Cationic Gemini Surfactants

A series of novel cationic gemini surfactants [C_nH_2n+1–O–CH₂–CH(OH)–CH₂–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? [ 3a (n = 12), 3b (n = 14) and 3c (n = 16)] having a 2‐hydroxy‐1,3‐oxypropylene group [?CH₂–CH(OH)–CH₂–O–] in the hydrophobic chain have been synthesized and characterized. Their water solubility, surface activity, foaming properties, and antibacterial activity have been examined. The critical micelle concentration (CMC) values of the novel cationic gemini surfactants are one to two orders of magnitude smaller than those of the corresponding monomeric surfactants. Furthermore, the novel cationic gemini surfactants have better water solubility and surface activity than the comparable [C_nH_2n+1–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? (n‐4‐n) geminis. The novel cationic gemini surfactants 3a and 3b also exhibit good foaming properties and show good antibacterial and antifungal activities.     

Surface and Biocidal Properties of Gemini Cationic Surfactants Based on Propoxylated 1,6-Diaminohexane and Alkyl Bromides

Two new classes of gemini cationic surfactants—hexanediyl-1,6-bis[(isopropylol) alkylammonium] dibromide {in the abbreviation form: C_nC₆C_n[iPr-OH] and C_nC₆C_n[iPr-OH]₂; alkyl: C_nH_{2n + 1} with n = 9, 10, 12 and 14}—have been synthesized by interaction of alkyl bromides with N,N′-di-(isopropylol)-1,6-diaminohexane and N,N,N′,N′-tetra-(isopropylol)-1,6-diaminohexane. The surface tension, electrical conductivity, and dynamic light scattering (DLS) techniques were used to investigate the aggregation properties of the gemini cationic surfactants in aqueous solution. The formation of critical aggregates at two concentrations in an aqueous solution from obtained gemini cationic surfactants were determined via the tensiometric method. Thus, these gemini cationic surfactants start to form aggregates at concentrations well below their critical micelle concentrations (CMC). The surface properties and the binding degree (β) of the opposite ion were tested against the length of the surfactant hydrocarbon chain and the number of the isopropylol groups in the head group. By applying the DLS technique, it was explored that how the number of isopropylol groups in gemini cationic surfactants with C₁₂H₂₅ chain affects the sizes of micelles at concentrations greater than CMC. It was discovered that the obtained gemini cationic surfactants have a biocidal character.     

Synthesis and Surface Tension Study of the Spacer Chain Length Effect on the Adsorption and Micellization Properties of a New Kind of Carboxylate Gemini Surfactant

A series of carboxylate gemini surfactants, which contain two hydrocarbon chains linked by amide groups, two carboxylate groups, a flexible alkane spacer were synthesized by three-step reactions and named alkylidene–bis-(N,N′-dodecyl-carboxypropylamides) (2C₁₂H₂₅CnAm; n = 2, 3, 4, 6, 8 is the number of methylene groups of the spacer), their structures were confirmed by FTIR,¹H NMR, and LC–MS/TOF, and their purity checked by HPLC. The micellar properties with increasing spacer chain length of these gemini surfactants were determined by surface tension methods. The critical micelle concentration (CMC) varies slightly with spacer chain length; surface tension at CMC(γ_CMC), the tendency of micellization versus adsorption, CMC/C₂₀, the minimum area per surfactant molecule at the air/solution interface (A_CMC), all decrease with increasing spacer chain length; surface reduction efficiency, pC₂₀, the surface excess at the air/solution interface (Г_CMC) increase with increasing spacer chain length. The results probably indicate that increasing spacer chain length of these carboxylate gemini surfactants will increase spacer incorporation into the double hydrophobic chain.     

Surface Activities, Foam Properties, HLB, and Krafft Point of Some n-Alkanesulfonates (C14–C18) with Different Isomeric Distributions

A homologue series of sodium secondary n-alkanesulfonates (C₁₄, C₁₆ and C₁₈) were obtained by photosulfochlorination process with two different reaction conditions. Different length chains with different isomeric distributions of n-alkanesulfonates are expected to present variations in physicochemical properties. In this investigation, the relationships between their isomeric distribution and their chain length and micellar behaviors were thoroughly explored. Their CMC at different temperatures were determined using specific conductivity and surface tension measurements. Through surface tension isotherms, the surface activities (??_CMC) were obtained. The surface absorption amounts (??_max) and the molecular areas (A _min) were calculated using Gibb??s equation. As expected, these surfactants exhibit good surface properties. It was shown that the CMC values increase with increasing the percentage of secondary isomers, with a surface tension decrease. It was also shown that the CMC values decrease with increasing chain length. The HLB values were calculated for each surfactant and the results obtained suggest that they are O/W emulsifiers. The foam properties of synthesized surfactants were evaluated and compared to those obtained for commercial samples. It was shown that the foamability is influenced both by the length of the hydrophobic moiety and the percentage of secondary isomers. It can be easily concluded that the C₁₄ sulfonates show the best foaming properties independently of their isomeric distribution. The Krafft point values obtained indicate that the micellization and the surfactant solubility mainly depend on the proportion of secondary isomers and the length of hydrophobic moiety.     

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,Surface Activity,Thermodynamic Parameters,and Performance Evaluation of Branched Carboxylate Gemini Surfactants

Three novel carboxylate gemini surfactants (3C_ntaDA, n = 8, 10, and 12) were synthesized by two simple steps, and their structures were characterized using FT-IR and ¹H NMR. The surface activities of these surfactants were obtained from surface tension measurements at different temperatures, and the surface parameters containing the critical micelle concentration (CMC), surface tension (γ), minimum surface area per molecule ( A_min ), and maximum surface excess concentration ( Γ_max ) were obtained from surface tension measurements. The experimental results show that 3C_ntaDA surfactants have higher surface activities compared with the corresponding conventional surfactants. The thermodynamic parameters of the micellization process were investigated, and the calculated results show that it was an exothermic and spontaneous process. The emulsification and foam performance of these surfactants were also evaluated at different concentrations at 298.15 K.     

Synthesis, Surface Active Properties of Novel Gemini Surfactants with Amide Groups and Rigid Spacers

A series of novel cationic gemini surfactants, bis-(N-(3-alkylamido-propyl)-N,N-dimethyl)-p-phenylenediammonium dichloride, were synthesized. The structures of the gemini surfactants were characterized by IR, ¹H NMR and ¹³C NMR. The Krafft temperatures of surfactants were determined through conductivity, the surface active properties in aqueous solution were studied at various temperatures by surface tension and conductivity. The thermodynamic functions of micellization process of the surfactants were also calculated by conductivity. The Krafft temperatures of the surfactants were 12, 13 and 28 °C. The values of CMC and Γ _max decreased with increasing the length of hydrophobic chains, but the values of CMC and α increased with increasing temperature. The process of micellization is a spontaneous, exothermic and entropy-driven process.     

Synthesis and surface properties of chemodegradable anionic surfactants: Sodium salts of sulfated 2-n-alkyl-5-hydroxymethyl-5-methyl-1,3-dioxanes

In acid-catalyzed reactions of long-chain aliphatic aldehydes (Ia-d) (a,R=n-C₅H₁₁; b,R=n-C₇H₁₅; c,R=n-C₉H₁₉; d,R=n-C₁₁H₂₃) with 1,1,1-tris(hydroxymethyl)-ethane (II), 2-n-alkyl-5-hydroxymethyl-5-methyl-1,3-dioxanes (IIIa-d) were obtained. Then they were reacted with SO₃·pyridine complex in dry carbon tetrachloride solution, to obtain trisubstituted derivatives of 1,3-dioxane (IVa-d). They constitute a new group of chemodegradable, acetal-type anionic surfactants, which may readily hydrolyze and oxidize to nonsurfactant compounds. Physical data of the new compounds and some surface properties, such as Krafft point, critical micelle concentration (CMC), surface tension of aqueous solution near CMC (γ_CMC) and wetting and foaming properties, were determined. Sodium salts of sulfated 2-n-alkyl-5-hydroxymethyl-5-methyl-1,3-dioxanes (IVa-d) exhibit aqueous solution properties similar to those of the well-known sodium alkyloligooxyethylene sulfates. Presence of the 5-methyl-1,3-dioxane moiety in molecules of compounds IVa-d introduces hydrophobic character comparable to the effect of three oxyethylene groups (-CH₂CH₂O-) or of two methylene groups (-CH₂-) of the alkyl chain in sodium alkyl ether sulfates [R(OCH₂CH₂)_mOSO₃Na] with equal R value. Part XXV in the series: Chemical Structure and Surface Activity. Part XXIV: A. Sokołowski, B. Burczyk, H.-R. Holzbauer, M. Herbst,Colloids Surfaces 57: 307 (1991).     

Gemini Surfactants Foam Formation Ability and Foam Stability Depends on Spacer Length

A series of cationic gemini surfactants containing different spacer length were synthesized and analyzed structurally. It was shown that the surface tension (σ) and critical micelle concentration (CMC), which had a maximum for the n-C₄H₈ spacer depended on the spacer length. The foaming ability and foam stability are high for the gemini surfactants with short spacers (C₂H₄ to n-C₄H₈), while longer spacers lead to a distinct decrease of these foam parameters. Foaming properties are discussed in terms of configuration and conformation of a surfactant molecule and in relation to micellization state kinetic.     

Chemical structure/property relationships in surfactants. 17. N-substituted-N-acyl glycinates in pure and synthetic hard river water

The surface properties [effectiveness of surface tension reduction (γ_CMC), critical micelle concentration (CMC), efficiency of surface tension reduction (pC ₂₀), maximum surface excess concentration (Γ_CMC), minimum area/molecule at the interface (A _min), and the CMC/C ₂₀) ratio] of well-purified N-substituted glycine derivatives, having the structural formula RC(O)N(R′)CH₂COONa, where RC(O)=lauroyl, myristoyl, or oleoyl, and R′=Et, Pr, Bu, CH₂CH₂OH or CH₂CH₂CH₂OCH₃, were investigated at 25°C in hard river water and distilled water. These surfactants show greater surface activity in hard river water than in distilled water. The effect of both the main alkyl chain R and the N-substituent R′ on surface properties was elucidated, the oleoyl group showing properties equivalent to that of a C₁₆ saturated acyl group. A linear relationship was observed between the pC ₂₀ or CMC values and the number of carbon atoms in the alkyl chain R or in R′ when it was alkyl. With increase in the number of carbon atoms in either R or the N-substituent R′ when it is alkyl, both pC ₂₀ and micelle-forming ability increase, although the effect of R′ on the foregoing two surface properties is lower than that of R. When R′ is (CH₂)₃OCH₃, however, the results suggest that R′ is only partly removed from contact with the aqueous phase either upon adsorption at the water/air interface or upon micellization. It increases A _min, is equivalent only to an ethyl group in its effect on pC ₂₀ and to a methyl group in its effect on CMC, and, in contrast to the effect of R′ when it is alkyl, produces no increase in the CMC/C ₂₀ ratio. As a result, γ_CMC increases with R when R′ is alkyl and decreases with R when R′ is (CH₂)₃OCH₃.     

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.     

Synthesis and Surface Properties of Anionic Gemini Surfactants having N-acylamide and Carboxylate Groups

A straightforward synthetic strategy to an anionic gemini surfactant having both N-acylamide and carboxylate groups in a molecule has been demonstrated. The surface properties of the anionic gemini surfactant, such as CMC (critical micelle concentration), C₂₀ (the concentration required to reduce the surface tension of the solvent by 20 mN/m), γ _CMC (the surface tension at the CMC), ∏ _CMC (the surface pressure at the CMC), Γ _max (the maximum surface excess concentration at the air/aqueous solution interface), A _min (the minimum area per surfactant molecule at the air/water interface), and the CMC/C₂₀ ratio (a measure of the tendency to form micelles relative to adsorbtion at the air/water interface), have been studied. The influence of the different concentrations of NaCl on the surface properties of the gemini surfactant has been discussed. The results have shown that the CMC values decreased with an increase in the concentration of NaCl indicating that the Na⁺ preferentially adsorbs onto the surface of the charged aggregate and facilitates the aggregate growth by suppressing the main impediment of electrostatic repulsion among head groups. Additionally, the values of Γ _max are always higher in salt solutions as compared to those in pure water due to their salting out effect. The larger pC₂₀ value indicates that the surfactant adsorbs more efficiently at the air/water interface and reduces surface tension more efficiently. In addition, the geminis in water show little or no break in their specific conductance versus surfactant molar concentration plots. This is attributable to protonation of the carboxylate group and strong Na⁺ release during micellization.     

Surface activity and premicellar aggregation of some novel diquaternary gemini surfactants

A series of novel cationic gemini surfactants, C _n H _2n+1 N⁺(CH₃)₂CH₂CHOHCHOHCH₂N⁺(CH₃)₂C _n H _2n+1 ·2Br⁻, have been synthesized, and their surface properties were investigated in water, 0.1 N NaCl, and 0.1 N NaBr at 25°C. From surface tension-log molar concentration plots, the pC₂₀, critical micelle concentration (CMC), and γ_CMC values have been determined, and the area/molecule at the aqueous solution/air interface was calculated. When the number of carbon atoms in the alkyl (hydrophobic) chains is above a certain number, which depends upon the molecular environment, the surface activity of the compounds is less than expected. This appears to be due to formation of small, soluble aggregates below the CMC. Equilibrium constants calculated for this aggregation indicate that a series of oligomers are formed.     

Mixed Micellization Study of Alkyltrimethylammonium and Alkyltriphenylphosphonium Bromides in Aqueous Solution

Mixed micellization study of cationic surfactants viz. alkyltrimethylammonium bromides (C_nTAB) and alkyltriphenylphosphonium bromides (C_nTPPB) with similar hydrophobic groups (C₁₂-, C₁₄-, and C₁₆-) was performed using tensiometry and UV–visible light spectrophotometry techniques. Critical micelle concentration (CMC) values of the single and binary surfactant mixtures were obtained from a plot of surface tension versus the logarithm of surfactant concentration (C _s). The degree of synergy and various mixed micelle parameters like interaction parameter (β), activity coefficients (f ^m ) and interfacial parameters like surface pressure (π _CMC), packing parameter (P), surface excess concentration (Г _max), surface tension at the CMC (γ _CMC), and minimum area per molecule (A _min) were evaluated using the regular solution theory (RST). Thermodynamic parameters were calculated using several proposed models which suggest the mixed micellar system to be more thermodynamically stable than their respective individual components. In addition, a dye solubilization study was performed using a spectrophotometric method to validate the CMC data obtained from tensiometric method. Conductometric measurements were also carried out for the mixture of C₁₂TAB + C₁₂TPPB only as it showed a more negative β, indicating a higher degree of synergism.     

Mixed Micellar Properties and Related Interaction Parameters of Butanediyl-1,4-bis(dodecyl dimethyl ammonium bromide) Gemini Surfactant with Nonionic Amphiphiles

Mixed micellization of cationic gemini surfactant butanediyl-1,4-bis(dimethyldodecylammonium bromide) with nonionic surfactants (sorbitan esters, alcohols and phenol ethoxylates) and triblock copolymers has been studied tensiometrically. Various physicochemical parameters of the studied systems including ideal CMC values, experimental and ideal micellar compositions, interaction parameters, activity coefficients of the components, etc. have been evaluated by considering theoretical models of Clint, Rubingh, Rosen and Maeda. The experimental critical micelle concentration (CMC) values of the mixed micelles were lower than the CMC values of the individual components and showed a negative deviation from ideal CMC (CMC*) values. The analysis reveals that the mole fractions of gemini are lower compared to the nonionic surfactants/triblock polymers and the values of ΔG _m ^° , ΔG _ad ^° , G _min and ΔG _ex ^m show that the spontaneity of the studied mixed micelles relatively decreases as the content of the gemini in the bulk phase increases.     

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.     

Micellization and Adsorption Behaviors of New Reactive Polymerizable Surfactants Based on Modified Nonyl Phenol Ethoxylates

The synthesis and characterization of a series of polymerizable surfactants based on alkyl phenol ethoxylate backbone and carboxylic or anhydride chain ends were investigated. Surface activities of these polymerizable surfactants were investigated to correlate their structure and their performances. The new bifunctional surfmers were prepared by reacting polyoxyethylene 4-nonyl-2-propylene-phenol nonionic reactive surfactants with maleic anhydride. The chemical structure of the prepared surfactants was characterized by ¹³C and ¹H NMR analyses. The surface activities of the modified polymerizable surfactants were measured from the adsorption isotherm measurements which were determined from the relationship between the concentrations and surface tension of surfactants in aqueous medium at different temperatures. Critical micelle concentration (CMC) values were determined for water soluble surfactants. It was found that CMC decreases with the incorporation of the anhydride and acid groups in the chemical structure of polyoxyethylene 4-nonyl -2-propylene-phenol nonionic surfactant. surface-active parameters such as area per molecule at the interface (A _min), surface excess concentration (Γ_max) and the effectiveness of surface tension reduction (π_CMC) were measured from the adsorption isotherms of the modified surfactants. Some thermodynamic data for the adsorption process were calculated and discussed. The data indicated that the new surfmers are more reactive than the simple polyoxyethylene 4-nonyl-2-propylene-phenol and more adsorbed at interfaces. We have performed a preliminary experiment to explore the emulsification efficiency of the newly synthesized reactive surfactants in equal volume oil–water emulsions. Different emulsion types and stabilities were obtained.     

Micellar and Surface Properties of Some Monomeric Surfactants and a Gemini Cationic Surfactant

The physicochemical and interfacial properties of the monomeric surfactants cetyltrimethyl ammonium bromide (CTAB), cetyltriphenyl phosphonium bromide (CTPB), tetradecyl triphenyl phosphonium bromide (TTPB), cetyldiethylethanol ammonium bromide (CDEEAB), cetyltrimethyl ammonium chloride (CTACl), tetradecyltrimethyl ammonium bromide (TTAB), and a gemini surfactant (C₁₆-3-C_16, 2Br⁻) at different pH (3.1, 7.0, and 7.75) have been investigated by conductivity and surface tension measurements at 300 K. The critical micellar concentration (CMC), degree of micellar ionization (α), surface excess concentration (Г_max), minimum surface area per molecule of surfactant (A _min), Gibbs free energy of micellization (∆G _m⁰), surface pressure at the CMC (π _CMC), and the Gibbs energy of adsorption (∆G _ads⁰) of the monomeric surfactants have also been determined. The CMC, α and Г_max, increase with increasing pH whereas A _min decreases.     

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.