Surface Tension Reduction Efficiency Research Articles

Adsorption layer structure formation at the air/water interface in aqueous mixtures of an anionic carboxylate gemini and a cationic surfactant

The surface adsorption of the O, O′-bis(sodium 2-lauricate)- p-benzenediol (C11 pPHCNa) and dodecyltrimethylammonium bromide (C 12TABr) aqueous mixtures was examined by surface tension method. Strong synergism between the two components was observed, which leaded to high effectiveness and efficiency in surface tension reduction. The maximum effectiveness and efficiency in surface tension reduction appeared at the mole fraction of C11 pPHCNa in the bulk ( α 1) being 0.33, where the two components equal electrical mixing in solution. The corresponding minimum surface tension ( γ cmc) and the total concentration required to reduce 20 mN m −1 surface tension of water ( C 20,T) were, respectively 25.2 mN m −1 and 2.02 × 10 −3 mmol L −1. The maximum apparent surface excess, Γ max was observed at α 1 = 0.1 rather than at α 1 = 0.33. The cause was attributed to two aspects: (1) the considerable fast diffusion rate of C 12TABr in comparison with C11 pPHCNa and (2) significantly high hydrophobicity of the latter. The unusually small apparent area of the adsorbed molecule suggested the surface aggregates formation. The pattern of the surface aggregates was further described as the double layers structure in the subsurface by analyzing the data of the total area of all adsorbed molecules.

Interaction of nonionic surfactant AEO9 with ionic surfactants

The interaction in two mixtures of a nonionic surfactant AEO9 (C12H25O(CH2CH2O)9H) and different ionic surfactants was investigated. The two mixtures were AEO9/sodium dodecyl sulfate (SDS) and AEO9/cetyltrimethylammonium bromide (CTAB) at molar fraction of AEO9, alpha(AEO9) The surface properties of the surfactants, critical micelle concentration (CMC), effectiveness of surface tension reduction (gamma(CMC)), maximum surface excess concentration (Gamma(max)) and minimum area per molecule at the air/solution interface (A(min)) were determined for both individual surfactants and their mixtures. The significant deviations from ideal behavior (attractive interactions) of the nonionic/ionic surfactant mixtures were determined. Mixtures of both AEO9/SDS and AEO9/CTAB exhibited synergism in surface tension reduction efficiency and mixed micelle formation, but neither exhibited synergism in surface tension reduction effectiveness.

Surface Properties of Gleditsia Saponin and Synergisms of Its Binary System

A gleditsia saponin (GS) is isolated and purified from the fruits of Gleditsia sinensis Lam. Its surface and thermodynamic properties in aqueous solution at 0, 15, 25, 35, 45, and 60°C have been investigated by surface tension measurement. The major data at 25°C are the critical micelle concentration (cmc), 1.10E‐3 mol · L−1; the surface tension at cmc (γ cmc ), 34.4 mN · m−1; the maximum surface excess concentration (Γmax), 2.33E‐6 mol · m2; the minimum area per molecule (A cmc ), 0.712 nm2; the standard adsorption energy (ΔG ad 0), −32.9 kJ · mol−1; and the standard micellization energy (ΔG m 0), −16.9 kJ · mol−1. The molecular interaction parameters, β s and β m , for the binary systems of GS with a cationic surfactant (C16H33NMe3Br), an anionic surfactant (C12H25SO3Na), and a nonionic surfactant (C8H17Ph(EO)10OH) have been determined. Based on the regular solution treatments of Rubingh, Rosen, and their coworkers, the conditions of synergism in surface tension reduction effectiveness have been extended. The condition to produce this synergism and the corresponding parameters at the maximum synergism point, i.e., the mole fractions of surfactant 1 in the solution phase (α1*), the critical micelle concentration of mixtures (cmc 12*), and the surface tension at this concentration (γ cmc12*), are given. The results show that of the three binary systems, synergism in micelle formation can occur only in the mixture of GS with cationic surfactants; synergism in surface tension reduction efficiency can occur in the mixture of GS with both cationic surfactant and nonionic surfactants, but, all the binary systems of GS with ionic and nonionic surfactants can show remarkable synergism in surface tension reduction effectiveness.

Surfactants and interfacial phenomena

Surfactants and interfacial phenomena

Surface and micellar properties of new nonionic gemini aldonamide-type surfactants

A new group of gemini aldonamide-type surfactants— N, N′-bisalkyl- N, N′-bis[(3-gluconylamide)propyl]ethylenediamines, N, N′-bisdodecyl- N, N′-bis[(3-glucoheptonylamide)propyl]ethylenediamine, and N, N′-bisalkyl- N, N′-bis[(3-lactobionylamide)propyl]ethylenediamines, (alkyl: n-C 8H 17, n-C 12H 25), were synthesized and characterized. The surface properties, such as surface excess concentration, Γ cmc, surface area demand per molecule, A min, efficiency in surface tension reduction, p C 20, the effectiveness of surface tension reduction, γ cmc, critical micelle concentration, cmc, and a measure of the tendency of the surfactant to adsorb at the aqueous/air interface relative to its tendency to form micelles in the bulk surfactant solution, cmc/ C 20, and standard free energy of micellization, Δ G mic 0, have been obtained by means of surface tension measurements. The standard fluorescence shift technique using PRODAN as a probe provide confirmation of the cmc values by an alternative method. Additionally, the micellar properties for the concentration near above the cmc have been characterized by the aggregation number, N agg. The presence of the dimeric segments with the aldonamide hydrophilic units in the surfactant molecule is found to be the source of their unusual physicochemical behavior. They are very efficient at adsorbing at the free surface and at forming micelles in water. Their critical micelle concentration values are remarkably low. They reveal remarkably low A min values in relation to conventional nonionic surfactants, which is unexpected from the molecular dimensions for the molecule but which is possible if one assumes some type of multilayer structure or a coherent interfacial film.

The interaction of an anionic gemini surfactant with conventional anionic surfactants

The interaction in two mixtures of an anionic gemini surfactant having N, N-dialkylamide and carboxylate groups in a molecule, (CH 2) 2[N(COC 11H 23)CH(CO 2H)CH 2(CO 2H)] 2 ·2NaOH (GA), and conventional anionic surfactants have been investigated in 0.1 M NaCl at pH 5.0. The two mixtures are GA/sodium dodecylsulfate (SDS) and GA/sodium N-dodecanoylglutamate (AGS) at a molar fraction of GA, α GA =0.25 . Mixtures of both GA/SDS and GA/AGS exhibit synergism in surface tension reduction effectiveness. The GA/SDS mixture also exhibits synergism in surface tension reduction efficiency and mixed micelle formation, whereas the GA/AGS mixture does not. The interaction in mixed adsorption film formation is stronger than that in mixed micelle formation for the two mixtures. The interaction in the formation of the mixed adsorption film and the mixed micelle for the GA/SDS mixture is stronger in both formations than that for the GA/AGS mixture. The stronger interaction for the GA/SDS mixture may be caused by the combination of the smaller minimum area per molecule at the air/water interface ( A min ) of the head groups in the GA molecule and the larger A min in the SDS molecule.

Synergism in mixtures of cationic surfactant and anionic copolymers

Surface tension measurements have been made in aqueous solutions of anionic hemiesters of an alternating copolymer of maleic acid and styrene, MAS- n with n=0–12, in the presence of dodecyltrimethylammonium bromide, DTAB. A synergistic aspect of surface tension reduction efficiency was observed for all systems studied. The pseudo-phase separation approach and regular solution approximation have been applied, and the interaction parameter, β, and the mole fraction of DTAB in the adsorbed layer (on a surfactant/repetitive unit basis), X, were obtained. Negative values of β, ranging from −3 to −11, were calculated. On the other hand, the molar fraction of DTAB varies from 0.52 to 0.26. These results are discussed in terms of hydrophobic effects on the distribution of the aggregates between the interface and the bulk of the solution. The conditions predicted by the model to obtain synergism in the tension reduction efficiency are completely satisfied in all cases.

Synthesis and Surface Properties of N-Alkyl-N-methylgluconamides and N-Alkyl-N-methyllactobionamides

Three series of nonionic N-alkylaldonamides, N-alkyl-N-methylgluconamides (Cn-MGA, Cn: n-C10H21, n-C12H25, n-C14H29, n-C16H33, and n-C18H37), N-alkyl-N-methyllactobionamides (Cn-MLA, alkyl as above-mentioned), and N-oleyl-N-methylglucon/lactobionamide, were synthesized in the reaction of an appropriate N-alkyl-N-methylamine with δ-D-glucolactone and lactobionic acid, respectively. Krafft temperatures of aqueous solutions and surface properties of these surfactants at 20°C, i.e., surface excess concentration, Γcmc, surface area demand per molecule, Amin, efficiency in surface tension reduction, pC20, effectiveness in surface tension reduction, Πcmc, critical micelle concentration, CMC, and CMC/C20 parameter as well as standard free energies of adsorption, ΔG°ads, and of micellization, ΔG°mic, were determined. It was shown that introduction of the methyl group to the amide nitrogen increased the solubility of the surfactants, which was confirmed by their Krafft temperatures. Lactobionamides are more water soluble than gluconamides. On the other hand, the Cn-MGA surfactants are more surface active than the respective Cn-MLA ones. This observation is based on the determined adsorption and micellization parameters. The presence of one double bond in a hydrocarbon chain as in oleyl-amides increases their hydrophilic character compared with that of saturated C18 derivatives. No distinct differences were observed between the Amin values obtained for both series studied, although they differ markedly in the size of the hydrophilic groups.

The Interaction of Alkylglycosides with Other Surfactants

The interaction of n-decyl-β-maltoside (C10M), n-decyl-β-glucoside (C10G), n-dodecyl-β-maltoside (C12M), 1:1 (molar) C10M/C10G mixtures, and 2:1 (molar) C12M/n-dodecyl-β-glucoside (C12G) mixtures with anionic, cationic, nonionic, and zwitterionic surfactants has been investigated. The non-glycosidic surfactants used were the the anionic surfactant sodium dodecylethoxy sulfate (C12ESNa), the cationic surfactants decyl trimethylammonium bromide (C10TMAB), dodecyl trimethylammonium chloride (C12TMAC), and tetradecylammonium bromide (C14TMAB), the nonionic surfactant dodecyl hexaethoxyethanol (C12EO7), and the zwitterionic surfactant dodecyl-N-benzyl-N-methylglycine (C12BMG). The surface properties of the surfactants, critical micelle concentration (CMC), effectiveness of surface tension reduction (γCMC), efficiency of surface tension reduction (pC20), maximum surface excess concentration (Γmax), minimum area per molecule at the air/solution interface (Amin), and the CMC/C20 ratio, were determined for both the individual surfactants and their mixtures. The glucosides and maltosides show no significant interaction with each other or with the nonionic surfactant C12EO7. The maltosides interact weakly with the cationic, anionic, and zwitterionic surfactants. The glucosides interact somewhat more strongly with the same surfactants. Interaction is even stronger when glucoside/maltoside mixtures are interacted with the non-glycosidic surfactant. As a result, synergism is most prone to be found in systems containing the non-glycosidic surfactant and glucoside/maltoside mixture.

Preparation and properties of new lactose‐based surfactants

AbstractA new group of nonionic saccharide‐based surfactants, N‐alkanoyl‐N‐methyllactitolamines (alkanoyl: decanoyl, lauroyl, myristoyl, palmitoyl, stearoyl), were synthesized and characterized. Surface properties such as critical micelle concentration, standard free energy of adsorption, standard free energy of micellization, surface tension reduction efficiency, effectiveness of surface tension reduction, surface excess concentration, and surface area demand per molecule as well as foaming properties (i.e., foam volume and foam stability), contact angle, antiraicrobial activity, and biodegradability were determined. The selected performance properties were evaluated in relation to commercially available alkyl polyglucosides (Glukopon 600 EC(HH)‐a Henkel product), and oligooxyethylenated decyl (C10E4) and dodecyl (E12E5) alcohols. The foaming‐stabilizing effect and contact angle suggest that the lactose‐derived surfactants that were studied share some common properties with alkyl polyglucosides that are different from those with an oligooxyethylene grouping. All tested N‐alkanoyl‐N‐methyllactitolamines were practically nontoxic to bacteria and yeasts. These compounds are readily biodegradable in the Closed Bottle test inoculated with activated sludge. N‐Alkanoyl‐N‐methyllactitolamines with lower chain lengths (C10–C14) biodegraded at a slightly faster rate. Biological properties showed that this class of compounds fulfills all requirements needed for environmental acceptance.

Surface activity and thermodynamic of micellization and adsorption for isooctylphenol ethoxylates, phosphate esters and their mixtures with N-diethoxylated perfluorooctanamide

Three nonionic surfactants; p-isooctylphenol ethoxylates p-[i-OPE10], p-[i-OPE15], and p-[i-OPE20], were phosphorylated to produce three anionic phosphate ester surfactants. In addition, N-diethoxylated perfluorooctanamide ( N-DEFOA) was also prepared. The surface and thermodynamic properties of the three types of surfactants and mixtures of the fluorocarbon surfactant (FC) with the hydrocarbon surfactants (HC) have been investigated. Surface tension as a function of concentration of the surfactant in aqueous solution was measured at 30, 40, 50 and 60°C, using the spinning drop technique. From these measurements the critical micelle concentration (CMC), the surface tension at the CMC ( γ CMC), the maximum surface excess concentration ( Γ max), the minimum area per molecule at the aqueous solution/air interface ( A min), and the effectiveness of surface tension reduction ( π CMC), were calculated. The thermodynamic parameters of micellization (Δ G mic, Δ H mic, Δ S mic) and of adsorption (Δ G ad, Δ H ad, Δ S ad) for these surfactants and their mixtures were also calculated. Structural effects on micellization, adsorption and effectiveness of surface tension reduction are discussed in terms of these parameters. The results show that the FC surfactant and its mixtures with HC surfactants enhance the efficiency in surface tension reduction and adsorption in the mixed monolayer at the aqueous solution/air interface, and also, reduce γ CMC and the tendency towards micellization.

Interfacial and micellar properties of some anionic/cationic binary surfactant systems. 1. Surface properties and prediction of surface tension

The surface tension equations of binary surfactant mixtures are established by combining the Szyszkowski equation for pure surfactant solutions and extended nonideal theory for mixed adsorption. They are then successfully applied to two relatively long-chain anionic/cationic binary surfactant systems: triethanolammonium dodecylpoly(oxyethylene)sulfate, as an anionic species (containing about 2 ethylene oxide units), mixed with dodecyltrimethylammonium bromide or hexadecyltrimethylammonium bromide. The composition of the mixed monolayer is mixing-ratio dependent and is slightly asymmetric: for overall equimolar mixtures, the larger mole fraction in the mixed monolayer is that of the more surface-active ion. The strong synergetic effects observed in the surface tension reduction efficiency are reflected by large negative βs parameters, according to regular solution theory. They can be interpreted by the more negative adsorption free energy of each surfactant and the smaller area occupied by surfactant hydrocarbon chains in the mixed monolayer.

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

AbstractThe surface properties [effectiveness of surface tension reduction (γCMC) critical micelle concentration (CMC), efficiency of surface tension reduction (pC20), maximal surface excess concentration (Γmax), minimal area/molecule at the interface (Amin), and the (CMC/C20) 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 γCMC 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.

Surface-active properties of particle size fractions in two humic acids

The relationships between surface active properties and humic acid (HA) particle sizes were investigated. Two HAs from an Ando soil and a Brown forest soil were separated into 6 particle size fractions by gel permeation chromatography. Surface-active properties characterized by surface excess value (\\gT mol cm-2), cross-sectional surface area per molecule (A nm2), critical micelle concentration (CMC g L-1), efficiency and effectiveness of water surface tension reduction were obtained by the measurement of the surface tension of HA solutions from different particle size fractions. For the HA from the Ando soil, except for the smallest particle size fraction, increasing particle size enhanced the efficiency of reduction of the water surface tension and decreased the CMC, while the effectiveness of reduction of the water surface tension was about the same. The surface activity of the HA from the Ando soil increased with increasing particle size. This phenomenon was similar to the surface activity of a homologous series of surfactants, which increased with increasing alkyl chain length. For the HA from the Brown forest soil, the smallest particle size fraction and three large fractions showed a high efficiency, namely a high surface activity. The smallest fraction from the Brown forest soil showed the highest efficiency and the lowest CMC value. In both HAs, the smallest particle size fraction showed exceptional surface-active properties compared with the other fractions and three fractions with large particle size showed a higher surface activity than other smaller fractions.

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

AbstractThe surface properties [effectiveness of surface tension reduction (γCMC), critical micelle concentration (CMC), efficiency of surface tension reduction (pC20), maximum surface excess concentration (ΓCMC), minimum area/molecule at the interface (Amin), and the CMC/C20) 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 pC20 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 pC20 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 Amin, is equivalent only to an ethyl group in its effect on pC20 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/C20 ratio. As a result, γCMC increases with R when R′ is alkyl and decreases with R when R′ is (CH2)3OCH3.

The Interaction of Some Novel Diquaternary Gemini Surfactants with Anionic Surfactants

The interactions of a series of novel cationic gemini surfactants, [CnH2n+1(CH3)2N+CH2CHOHCHOHCH2(CH3)2N+CnH2n+1]22Br−(symbolized (CnN)2), with conventional surfactants (containing a single hydrophilic and a single hydrophobic group in the molecule) have been investigated. It is found that (C8N)2and (C10N)2have very strong interactions with the anionic surfactants C10H21SO3Na, C12H25SO3Na, and C12H25(C2H4O)4SO4Na, producing marked synergism in surface tension reduction efficiency and effectiveness and in mixed micelle formation in H2O, 0.1MNaBr, and 0.1MNaCl. In contrast to this, (C12N)2shows no synergism at all with C12H25SO3Na and has a much weaker synergistic interaction with C12H25(C2H4O)4SO4Na. It is proposed that extraordinarily strong interaction between the (C12N)2and C12H25SO3Na produces small, soluble, nonmicellar aggregates having no surface activity that decrease the monomer concentrations of the component surfactants, thereby reducing the surface activity of the system. Equilibrium constant calculations for this aggregate formation indicate that the two surfactants are present in a 1:1 molar ratio.

Effect of Hard River Water on the Surface Properties of Surfactants

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 max ), minimum area/molecule at the interface (A min ), and the (CMC/C 20 ) ratio] of well-purified anionic, nonionic, and cationic surfactants, some of which are widely used in daily chemical and industrial products, were investigated at 25 °C in hard river water. The studied surfactants show somewhat greater surface activity in hard river water than in distilled water, but in particular, for anionic surfactants a marked effect of hard river water on surface active properties was observed. The effect of hard river water on surface active properties is, in decreasing order, anionics > cationics > nonionics. For alkyl poly(oxyethylene) glycols, the effect on surface properties is interpreted in terms of complex formation between the ether oxygen atoms of the poly(oxyethylene) group and divalent hardness ions. The linear relationship between the pC 20 or CMC values and the number of carbon atoms in the alkyl chain observed in distilled water was confirmed in hard river water. For alkyl poly(oxyethylene) sulfates, the slope of the plot indicates an effect of the alkyl chain on adsorption at the air/water interface or on micellization similar to that observed for nonionic surfactants in distilled water.

Equilibrium Adsorption and Tension of Binary Surfactant Mixtures at the Air/Water Interface

The nonideal adsorbed solution model (NAS) is extended to the air/water interface for determining the surface tension of aqueous binary surfactant mixtures with molecules of different size, surface activity, and nonideal interactions. The regular solution theory is used for modeling the nonideal interactions between the adsorbed molecules and in the micelles. Two mixing parameters β σ and β m are used for fitting data for premicellar and micellar concentrations. This model can also be extended to account for molar area changes upon mixing in the monolayer or more complex nonideal interactions. Synergism in surface tension reduction efficiency can be predicted with this model. The ranges of mole fractions and concentrations for the existence of synergism can be determined. Tension data of two nonionic binary mixtures, C 12 E 8 /SDS (from the literature) and C 12 E 6 /Triton X-100, fit this model well. New tension data for C 12 E 5 /Triton X-100 are reported, and they are synergistic for a specific range of concentrations. Moreover, the surface coverages and compositions for the two nonionic mixtures are calculated with the NAS model. These calculations show that the larger molecules adsorb at the interface more favorably at low concentrations than at high concentrations.

Synergism in binary mixtures of surfactants 12. Mixtures containing surfactants with two hydrophilic and two or three hydrophobic groups

Molecular interactions between several anionic sulfonate surfactants containing two hydrophilic groups and two or three hydrophobic groups in the molecule (gemini surfactants) and a zwitterionic surfactant ( N, N-dimethyl-1-tetradecanamine oxide) or a polyoxyethylenated non-ionic surfactant (C 12H 25(OC 2H 4) 7OH or C 12H 25(OC 2H 4) 8OH) were measured at 25°C in aqueous 0.1 M NaCl solution. The strength of the interaction with the zwitterionic surfactant decreases with increase in the minimum area per sulfonate group of the gemini surfactant at the air/water interface. The interaction with the zwitterionic surfactant or the polyoxyethylenated non-ionic surfactant is also weakened by the presence of multiple ether linkages in the hydrophilic group of the gemini surfactant. The latter surfactants with these linkages show a smaller increase, compared with gemini surfactants without them, in their interaction with the zwitterionic surfactant upon reduction of the pH of the solution. They also show an increase with this change in their area per molecule at the air/water interface and an increase in their interaction with an alkanesulfonate surfactant (C 12H 25SO 3Na), increases not shown when neither surfactant has multiple ether linkages in the molecule. It is suggested that the relative ease of protonation of the multiple ether oxygen atoms in the doubly charged anionic gemini molecule accounts for these observations. The interaction in mixed micelles is much weaker than in mixed monolayers at the air/water interface; this is attributed to the difficulty of incorporating a surfactant with multiple hydrophobic groups into a micelle. The compounds studied all show synergism in surface tension reduction efficiency and effectiveness when mixed with the amine oxides, consistent with the synergism parameters. They also show synergism in mixed micelle formation with the amine oxide, except for a compound with three alkyl chains and one with a trioxyethylene group in the hydrophilic part. This is attributed to steric inhibition of micelle formation. As a result of protonation, the anionic gemini surfactants with multiple ether oxygen atoms in the molecule show little or no synergism when mixed with a polyoxyethylenated non-ionic surfactant. Synergism in the surface tension reduction effectiveness for these compounds when mixed with an alkanesulfonate at a low pH, however, is indicated.

Synergism in Binary Mixture of Surfactants: 11. Mixtures Containing Mono- and Disulfonated Alkyl- and Dialkyldiphenylethers

Interaction and synergism at 25°C of some alkyl- and dialkyldiphenylether mono- and disulfonates with a second surfactant containing a single hydrophilic and a single hydrophobic group (a nonionic, a betaine, or an amine oxide type of surfactant) in aqueous solutions containing swamping amounts of NaCl were studied by calculating interaction (β) parameters from surface tension-concentration data. Attractive interaction in mixed monolayers at the aqueous solution/water interface increased in the order: monoalkyl monosulfonate (MAMS) < monoalkyl disulfonate (MADS) < dialkyl disulfonate (DADS). In mixed micelles, by contrast, the DADS interaction was always weaker than that of either the MAMS or MADS. This is believed to be due to greater steric inhibition of micelle formation by the DADS structure. As a result of these differences in interaction, the DADS (gemini-type) structure is more prone than the other two types of structures to show synergism in both surface tension reduction efficiency and effectiveness, and less prone to show synergism in mixed micelle formation.