Equilibrium Surface Tension Measurements Research Articles

Dynamic Interfacial Properties and Foamability of DoTAB/SiO2 Mixtures

The interaction between nanoparticles and cationic surfactants is an exciting and emerging field in interfacial science. This area of research holds significant promise, linking fundamental principles to practical applications in a variety of industries, including chemical processes, biomedical applications and the petroleum industry. This study explores the interaction between dodecyltrimethylammonium bromide (DoTAB) and silica (SiO2) nanoparticles, investigating their influence on dynamic interfacial properties and foam characteristics. Through equilibrium and dynamic surface tension measurements, along with examining the dilational visco-elasticity behavior, this research reveals the complex surface behavior of DoTAB/SiO2 mixtures compared to individual surfactant solutions. The foamability and stability experiments indicate that the addition of SiO2 significantly improves the foam stability. Notably, stable foams are achieved at low SiO2 concentrations, suggesting a cost-effective approach to enhancing the foam stability. This study identifies the optimal stability conditions for 12 mM DoTAB solutions, emphasizing the crucial role of the critical aggregation concentration region. These findings offer valuable insights for designing surfactant-nanoparticle formulations to enhance foam performance in various industrial applications.

Effect of Oxyethylene Groups of Fatty Alcohol Polyoxyethylene Ether Sodium Sulfates on Equilibrium and Dynamic Surface Tension in Relation to Wetting Properties

Abstract The effect of hydrophilic chain of surfactants fatty alcohol polyoxyethylene ether sodium sulphates (AEnS, n = 2, 3, 7) on surface properties and wetting properties was investigated by the measurement of equilibrium surface tension, dynamic surface tension and dynamic contact angle. The fatty alcohol polyoxyethylene ether sodium sulphates with different head group sizes were used. From the results of equilibrium surface tension measurements, we could obtain the critical micellisation concentration, adsorption efficiency, maximum surface excess concentration and Langmuir equilibrium adsorption constant at air/liquid interface. The dynamic surface tension results showed that the adsorption of aqueous solutions at the air/liquid interface follows a mixed-diffusion kinetic adsorption mechanism. In conclusion, for both studied surfactant, the longer the oxyethylene chains, the higher the maximum rate of surface tension reduction, the higher the diffusivity and wetting properties in terms of contact angle.

Interfacial complexation of a neutral amphiphilic ‘tardigrade’ co-polymer with a cationic surfactant: Transition from synergy to competition

HypothesisNeutral amphiphilic PEG-g-PVAc co-polymer (a “tardigrade” polymer consisting of a hydrophilic polyethylene glycol, PEG, backbone with hydrophobic polyvinyl acetate, PVAc, grafts) can form complexes at the air–water interface with cationic dodecyltrimethylammonium bromide (DTAB) via self-assembly. Compared to anionic SDS, cationic DTAB headgroups are expected to interact strongly with the negatively charged OH– groups from the partial dissociation of the PVAc grafts. We anticipate a transition from synergistic to competitive behaviour, which is expected to be dependent on the surfactant structural characteristics and concentration. ExperimentsDTAB/PEG-g-PVAc mixtures were investigated using a combination of dynamic and equilibrium surface tension measurements, neutron reflectivity (NR) at the air–water interface, and foaming tests. We varied the concentrations of both the DTAB (0.05 to 5 critical micelle concentration, cmc) and that of PEG-g-PVAc (0.2 and 2 critical aggregation concentration, cac). FindingsOur results show that the interfacial interactions between DTAB and PEG-g-PVAc were both synergistic and antagonistic, depending sensitively on the surfactant concentration. At DTAB concentrations below its cmc, a pronounced cooperative adsorption behaviour was likely driven by the hydrophobic interactions between the DTAB tail and the PVAc grafts and the attraction between the DTAB headgroups and the partially dissociated –O- groups in the partially hydrolysed PVAc grafts, forming a mixed layer. This synergistic adsorption behaviour transitioned to a competitive adsorption behaviour at DTAB concentrations above its cmc, leading to polymer-surfactant partition, forming a “hanging” polymer layer underlying a surfactant monolayer at the interface. We postulate that DTAB/PEG-g-PVAc complexation in the bulk contributed to partial depletion of the mixture from the interface. We therefore consider this polymer/surfactant system to be a moderately interacting system at the air–water interface. No discernible differences in the foaming behaviour were observed between the DTAB/PEG-g-PVAc systems and the pure surfactant. Our results suggest that surfactant headgroup characteristics (particularly charges) were crucial in determining the structure and composition of polymer-surfactant complexes at the air–water interface, as well as the foamability and foam stability, whilst the coexistence of the synergistic and competitive adsorption behaviour is attributed to the unique architecture of the tardigrade polymer with amphiphilicity and partial charge, facilitating different surfactant-polymer interactions at different DTAB concentrations.

Thermodynamically stable structure of hydroxy alkane sulfonate surfactant monomers in water achieving high water solubility and a low CMC.

Although sodium internal olefin sulfonates (IOSs) derived from petrochemicals are known to act as anionic surfactants, these compounds have few practical applications and their interfacial properties have not been examined in detail because they have complex compositions and are challenging to prepare. However, IOSs obtained from vegetable oils have recently been applied to detergents. The present work represents the first study of the IOS sodium 5-hydroxyhexadecane-4-sulfonate (C16-4S-5OH) as a pure substance. The properties of C16-4S-5OH in aqueous solution were assessed by differential scanning calorimetry, equilibrium surface tension measurements, Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. This compound was found to have a low Krafft point and a low CMC, both of which are necessary for a modern sustainable surfactant. Although these two characteristics are normally difficult to achieve simultaneously, this work demonstrated that C16-4S-5OH in aqueous solution has a highly fixed stereostructure that enables both properties to be achieved. The C16 main carbon chain of this compound acts as a C12 and a C4 chain both oriented in the same direction, while the hydrophilic sulfo and hydroxy head groups form a rigid cyclic moiety including two carbons of the C16 alkyl chain based on hydrogen bonding. This highly fixed molecular structure of the C16-4S-5OH in water is maintained in the monomer and micellar states below and above the CMC, respectively.

Dynamic Surface Tension of Surfactants in the Presence of High Salt Concentrations

We study the influence of high NaCl concentrations on the equilibrium and dynamic surface tensions of ionic (CTAB) and nonionic (Tween 80) surfactant solutions. Equilibrium surface tension measurements show that NaCl significantly reduces the critical micellar concentration (CMC) of CTAB but has no effect on the CMC of Tween 80. Dynamic surface tension measurements allow comparing the surface tension as a function of time for pure surfactant solutions and in the presence of NaCl. For the ionic surfactant, the dynamics agree with the usual diffusion-limited interfacial adsorption kinetics; however, the kinetics become orders of magnitude slower when NaCl is present. Sum-frequency generation spectroscopy experiments and the equilibrium adsorption measurements show that the presence of NaCl in CTAB solution leads to the formation of ion pairs at the surface, thereby neutralizing the charge of the head group of CTAB. This change, however, is not able to account for the slowing down of adsorption dynamics; we find that it is rather the decreases in the monomer concentration (CMC) in the presence of salt which has the major influence. For the nonionic surfactant, the kinetics of interfacial tension is seen to be already very slow, and the addition of salt does not influence it further. This also correlates very well to the very low CMC of Tween 80.

Properties of Binary Mixture of Cetyl Diphenyl Ether Disulfonate and Linear Alkylbenzene Sulfonate

Abstract The surface properties of the binary mixture of cetyl diphenyl ether disulfonate (C16-MADS) and linear alkylbenzene sulfonate (LAS) have been investigated by salinity and hardness tolerance, equilibrium surface tension, wettability, foam and emulsification measurements. The results show that with increasing mass ratio of LAS in the C16-MADS/LAS mixed system, the ability to reduce the surface tension of the solution is improved. The wetting performance is also improved. The critical micelle concentration (CMC) values are increased first, then decreased, and are higher than the ideal CMC values, which indicates that there is an antagonistic effect that is not conducive to the formation of mixed micelles between C16-MADS and LAS. In addition, the C16-MADS/LAS system improves the hard water resistance of LAS and reduces the foam properties of LAS.

Synthesis and Properties of Novel Catanionic Surfactant Phosphonium Benzene Sulfonate

Abstract A new type of catanionic surfactant phosphonium benzene sulfonate was synthesized by quaternization of triphenyl phosphine with dimethyl carbonate and followed by anion exchange with alkyl benzene sulfonic acid. The molecular structure was characterized by FT-IR, 1H-NMR, and 31P-NMR. The thermal stability of phosphonium benzene sulfonate was evaluated by thermogravimetric analysis (TGA). Its surface properties were studied systematically through equilibrium surface tension, electrical conductivity, and dynamic surface tension measurements. The wettability, foam properties, and emulsification of phosphonium benzene sulfonate were estimated in this paper. TGA results revealed that it has an excellent thermostability and could be used below 350 °C. Equilibrium surface tension results indicated that it has a low critical micelle concentration (CMC, about 0.10 mmol/L), lower than that of ammonium benzene sulfonate and sodium dodecyl benzene sulfonate. Furthermore, the micellization of phosphonium benzene sulfonate in aqueous solution is an entropy-driven spontaneous process. The adsorption process of phosphonium benzenesulfonate at the air-liquid interface is controlled by hybrid kinetic adsorption. Moreover, it has excellent wetting and emulsifying properties and low foam properties.

Synthesis and Physicochemical Properties of Novel Phenyl-Containing Sulfobetaine Surfactants

A novel series of sulfobetaine surfactants, 3-((4-(alkoxy)-3,5-dimethylbenzyl) dimethylammonio)-2-hydroxy-propane-1-sulfonate (CnOBSb, n = 12, 14, and 16), were synthesized for the first time. The chemical structures of products were characterized by high-resolution mass spectra, 1H NMR, and 13C NMR spectrometry. The physicochemical properties of CnOBSb were studied by thermogravimetric analysis, equilibrium surface tension measurement, steady-state fluorescence, dynamic light scattering (DLS), and cryogenic transmission electron microscopy (cryo-TEM). The results demonstrated that surface tension values of CnOBSb are in the range of 28.32–30.14 mN/m at a fairly low critical micelle concentration (cmc). The adsorption and micellization properties of CnOBSb were dependent on the hydrocarbon chain length and presence of phenyl group. The results of DLS and cryo-TEM measurements revealed that CnOBSb molecules spontaneously formed vesicles in aqueous solution above the cmc. Furthermore, the application proper...

Methyltriphenylphosphonium carboxylate ionic liquids: Green synthesis, adsorption and aggregation behavior in aqueous solution

In this paper, a series of methyltriphenylphosphonium carboxylate room temperature ionic liquids [Ph3PCH3][CnH2n+1COO] with different alkyl chain length (n = 7, 9, 11, 13, 15, 17) have been synthesized by quaternization of triphenylphosphine (TPP) with dimethyl carbonate (DMC) and followed anion exchange with different carboxylic acids. The synthesis route is not only simple, but also can avoid problems such as toxicity, environmental pollution and equipment corrosion. The structures of these compounds were characterized by FT-IR and 1H-NMR. Meanwhile, their surface adsorption and aggregation behavior in aqueous solution have been investigated by equilibrium surface tension, electrical conductivity and transmission electron microscopy (TEM) measurements. Furthermore, the impact of alkyl chain length on their surface adsorption and aggregation behavior were also investigated. TEM results indicated that methyltriphenylphosphonium carboxylate ionic liquid surfactants could self-assemble into regular spherical aggregates in aqueous solution. The diameter of the spherical aggregates is about 50 ∼ 100 nanometers and does not change much with the change of alkyl chain length.

Synergism and Interfacial Property Study of Sodium Lauryl Ether Sulfate and Polysorbate 80 at the Air–Water Interface

AbstractAdsorption and micellization behavior of sodium lauryl ether sulfate (SLES) and Polysorbate 80 (PS80) was investigated using equilibrium and dynamic surface tension and foaming measurements. Critical micelle concentration (CMC) was determined using surface tension and dye (Sudan red III) solubilization method with the help of the Wilhelmy plate method and ultraviolet–visible spectroscopic method, respectively. The strength of the interaction for micellization and adsorption between the mixtures are calculated using the β interaction parameter. The SLES‐PS80 mixture shows synergistic interaction with β = −8.0. The dynamic and foaming behavior at constant bulk concentration showed a higher t * value with lowest foaming at 50% mole fraction of SLES. The emulsification index (EI) of pure SLES, pure PS 80, and 1:1 SLES‐PS 80 composition was studied using neem, karanja, and sunflower oils. Karanja and sunflower oils show a higher EI for mixture than the pure surfactants, whereas neem shows a lower EI for mixture than pure surfactants.

Spontaneous vesicle formation and vesicle-to-micelle transition of sodium 2-ketooctanate in water

Single-tailed short-chain alkyl keto-acids/salts, a class of fatty acid/salt derivatives, such as sodium 2-ketooctanate (KOCOONa), are a kind of weakly acid/salt type amphiphiles and plausible prebiotic molecules, and the current understanding of their aggregation behavior in aqueous solutions is still limited. Herein, the aggregation behavior of KOCOONa in aqueous solution was studied by changing its concentration (C), using equilibrium surface tension, conductivity, and fluorescence measurements. The aggregates formed were characterized using freeze-fracture and cryogenic transmission electron microscopy, dynamic light scattering, atomic force microscopy, and confocal laser scanning microscopy. A concentration-driven stepwise aggregation was identified in the KOCOONa solution. Vesicles can spontaneously form from the single-component aqueous solution, with a critical vesicle concentration (CVC) of ∼15mM, which is obviously lower than that of octanoic acid/salt (120–200mM). With increasing C, a vesicle-to-micelle transition can occur, showing a critical micelle concentration (CMC) of ∼80mM. In addition, the membrane permeability of the KOCOONa vesicles was examined using small-size Calcein and large-size FITC-BSA as fluorescence probes, showing a size-selective permeability, similar to short-chain (C8-C11) fatty acid vesicles. For the first time, the aggregation behavior of single-tailed keto-acid salt surfactant is reported.

Adsorption of ionic surfactants at microscopic air-water interfaces using the micropipette interfacial area-expansion method: Measurement of the diffusion coefficient and renormalization of the mean ionic activity for SDS

The dynamic adsorption of ionic surfactants at air-water interfaces have been less-well studied than that of the simpler non-ionics since experimental limitations on dynamic surface tension (DST) measurements create inconsistencies in their kinetic analysis. Using our newly designed “Micropipette interfacial area-expansion method”, we have measured and evaluated both equilibrium and dynamic adsorption of a well-known anionic surfactant, sodium dodecyl sulphate (SDS), in the absence or presence of 100mM NaCl. Our focus was to determine if and to what extent the inclusion of a new correction parameter for the “ideal ionic activity”, A±i, can renormalize both equilibrium and dynamic surface tension measurements and provide better estimates of the diffusion coefficient of ionic surfactants in aqueous media obtained from electroneutral models, namely extended Frumkin isotherm and Ward-Tordai adsorption models. We found that the estimated value of the new parameter, A±i=0.29, is key to obtain the diffusion coefficient D=5.3±0.3×10−6cm2/s for SDS, in excellent agreement with the literature. These new technique and analyses can now be applied to study the interfacial adsorption of a range of both ionic and non-ionic surface-active molecules, including the potentially slower-diffusing polymers and biological materials like lipids, peptides, and proteins.

Capture of LPS traces in aqueous solutions by tectomers of four-antennary oligoglycines

The properties of aqueous solutions containing trace quantities of Lipopolysaccharide from bacteria Escherichia coli EH100 (LPS) and four-antennary oligoglycine C-(CH2-NH-Gly7)4*4HCl (T4) are investigated. The major aim is to elucidate the effect of endotoxin on the properties of the mixed LPS/T4 systems. Dynamic and equilibrium surface tension measurements are performed; surface dilational rheology of the adsorption layers at air/solution interface is studied; the drainage kinetics and stability of microscopic foam films are investigated. The obtained data present ample experimental evidences for the formation of bulk LPS/tectomer complexes which have amphiphilic properties. The specific goal is to outline details about the conditions for effective seizure of the endotoxin by T4 solutions. The results suggest that the self-assemblies (tectomers) of four-antennary oligoglycine may be used for registration of LPS traces. The study outcomes back up the idea that aqueous solutions of four-antennary oligoglycine may be used for capture of endotoxins in aqueous systems.

Experimental study on surface activity of surfactants on their ability to cleaning oil contaminations

In order to obtain a recipe for an effective degreasing agent, a selection of suitable surfactants is required. The present investigation addresses essentially the determination and comparison of the static and dynamic adsorption as well as wetting properties of selected surfactants and their binary mixtures which are potential components of the degreasing compositions. Equilibrium surface/interfacial tension in the air/water system for individual compounds and their binary mixtures were measured by du Nouy ring method. Moreover, the interfacial properties of binary surfactant mixtures with different polarity were investigated. The experimentally obtained isotherms: surface tension of the air/water systems and interfacial tension of oil/water systems for all investigated surfactants allowed to compare the surface activity of compounds considered. Surface and micellar properties of surfactants and their mixtures were discussed on the basis of equilibrium surface tension measurements and the study of kinetics of adsorption. The Rosen theory was used to characterize the synergism effects observed in the case of systems with binary surfactant mixture. The results indicated that the studied compounds reveal both different efficiency as well as different effectiveness of adsorption in the air/water system. Some of analysed binary surfactant mixtures show strong synergistic effects in lowering the surface tension and in the wettability of solid surfaces. The wetting properties of considered compounds strongly depend on the character of wetting surface. The dynamics of adsorption in considered systems is significantly affected by the concentration of surfactant solution. Generally, the efficiency of lowering surface tension is significantly higher in the micellar solutions. The results obtained allow to select mixture of nonionic surfactant and amphoteric one as potential components of the degreasing compositions.

A multitechnique approach on adsorption, self-assembly and quercetin solubilization by Tetronics® micelles in aqueous solutions modulated by glycine

Ethylene oxide-propylene oxide (EO-PO) block copolymer micelles are useful potential nanoreservoirs for the delivery of hydrophobic drugs. Considering that glycine is an excipient and can favorably affect the surface/micellar behavior and thus improve solubilization power/dispersion stability/wetting characteristics we have reported here studies on aqueous solution behavior of two commercially available branched block copolymers (Tetronics®) with differing hydrophobicities namely Tetronics® 1307 and 1304, hereafter referred as T1307 and T1304, in the presence of glycine. Steady state fluorescence studies using pyrene as a probe, equilibrium and dynamic surface tension measurements, wetting and dispersion stability studies of Teflon (polytetrafluoroethylene; PTFE) and solubilization studies of a hydrophobic antioxidant/anticancer drug quercetin (QN) have been examined. The cloud point (CP) and critical micelle temperature (CMT) decrease while micelle hydrodynamic size (Dh) increases with the addition of glycine as well as on loading of the drug in the micelles. Water penetration through packed PTFE powder and dynamic surface tension confirm the enhanced micellization process for aqueous Tetronic® solutions in presence of glycine and accordingly restricted diffusion for the surfactant molecules towards air-water and PTFE-water interface. The contact angles for Tetronic® solutions in presence of glycine indicate moderate decrease. The pressure-area curves of the copolymers in water and glycine solutions were also constructed. Surface and micellar properties of copolymers are markedly altered in the presence of glycine and can be tuned for use of these nanocarriers in delivery systems.

Synthesis and Properties of Dioctyl Diphenyl Ether Disulfonate Gemini Surfactant

AbstractThe surfactants dioctyl diphenyl ether disulfonate gemini (C8-DADS) and monohexadecyl diphenyl ether disulfonate (C16-MADS) were synthesized by Friedel-Crafts alkylation, followed by sulfonation and neutralization. Sulfated zirconia was prepared by the impregnation method and used to catalyze the alkylation reaction. Equilibrium surface tension measurements show that C8-DADS has a lower critical micelle concentration (CMC), surface tension at CMC (γcmc) and minimum area per molecule (Amin), higher efficiency of adsorption at the surface (pC20) than C16-MADS, implying that C8-DADS has a higher surface activity. The emulsifying ability of C8-DADS is better than that of C16-MADS. The salinity and hardness tolerance property of C16-MADS is superior to that of C8-DADS.

Solution Properties of Dissymmetric Sulfonate-type Anionic Gemini Surfactants.

Dissymmetric and symmetric anionic gemini surfactants, N-alkyl-N'-alkyl-N,N'dipropanesulfonylethylenediamine (CmCnSul, where m and n represent alkyl chain lengths of m-n = 4-16, 6-14, 8-12, 10-10, and 12-12), were synthesized by two- or three-step reactions. Their physicochemical properties were characterized by equilibrium surface tension measurements, steady-state fluorescence spectroscopy of pyrene, and dynamic light scattering. The critical micelle concentration (CMC) of the dissymmetric surfactants C4C16Sul, C6C14Sul, and C8C12Sul was slightly lower than that of the symmetric surfactant C10C10Sul. The occupied area per molecule (A) of C8C12Sul was smaller than that of C10C10Sul, indicating that C8C12Sul has a high surface activity. However, the increase in the degree of dissymmetry from C8C12Sul to C6C14Sul and then to C4C16Sul resulted in high surface tension and large A. Based on the surface tension, the standard free energies of micellization (∆G°mic) and adsorption (∆G°ads), the efficiency of surface adsorption (pC20), and the effectiveness of surface adsorption (CMC/C20) were obtained. These parameters suggested that C8C12Sul formed micelles more readily than the other surfactants. The properties determined from the surface tension indicated that C8C12Sul's ability is intermediate between those of C10C10Sul and C12C12Sul. The pyrene fluorescence and dynamic light scattering results revealed that the micelle size depends on the longer of the two alkyl chains in dissymmetric surfactants.

Sulfated Zirconium Catalyst for Synthesis of Dialkylated Diphenylether Disulfonate Gemini Surfactants

AbstractDialkylated diphenylether disulfonate with different alkyl chain lengths (Cn‐DADS, n = 8, 10 and 12) has been synthesized by Friedel‐Crafts alkylation of olefins (C8, C10 and C12) and diphenyl oxide, followed by sulfonation and neutralization with fuming sulfuric acid. Sulfated zirconia solid acids were prepared and used to catalyze the alkylation reaction. The structure of sulfated zirconia solid acids was identified by infrared spectroscopy. The title compounds were confirmed by infrared spectroscopy and electrospray ionization‐mass spectrometry. Equilibrium surface tension measurements show that the critical micelle concentration (CMC) decreases with an increase in chain length, and the surface tension at CMC (γcmc) of C8‐DADS is the lowest. The minimum area per molecule (Amin) values of Cn‐DADS increase, while the surface excess concentration (Γmax) values decrease with the increase of the alkyl chain length. C10‐DADS has the highest pC20 and CMC/C20 among Cn‐DADS.

Synthesis and Interfacial Activity of Novel Heterogemini Sulfobetaines in Aqueous Solution.

Three new heterogemini sulfobetaines and their chloride salts were synthesised. The interfacial activities of the obtained chlorides in aqueous solution were studied by equilibrium and dynamic surface tension measurements. The critical micelle concentration, surface excess concentration, minimum area per surfactant molecule and standard Gibbs energy of adsorption as well as micelle lifetime and diffusion coefficient were determined. The adsorption properties and micelle lifetime of these compounds significantly depend on the length of alkyl chain. The critical micelle concentration decreases with increasing chain length of the compounds considered. The values of the diffusion coefficient of N-alkyl-N-methyl-N-(3-sulfopropyl)-6-(N-alkyl-N-methylamino)hexylammonium chloride tend to decrease as the concentration is increased.

Interfacial layer properties and foam film drainage kinetics of aqueous solutions of hexadecyltrimethylammonium chloride

Comparative studies of adsorption layer properties at the air/solution interface – dynamic and equilibrium surface tension measurements, surface dilatational rheology – and the drainage behaviour of microscopic foam films of aqueous solutions of hexadecyltrimethylammonium chloride (cetyltrimethylammonium chloride, CTAC), are performed within a broad surfactant concentration range. Two different concentrations of the added electrolyte (sodium chloride, NaCl) are investigated: 0.1M and 0.5M. The interfacial layer characteristics are studied using profile analysis tensiometer (PAT-1). The foam film drainage kinetics is investigated by the microinterferometric technique of Scheludko–Exerowa. Concerted onset of specific peculiarities is established for both adsorption layer properties and the foam film parameters. A remarkably good correlation is established between the run of the dynamic and equilibrium surface tension isotherms, the course of the surface dilatational elasticity and the peculiarities of drainage kinetics and film stability against the surfactant concentration within each of these concentration intervals. The obtained results shed additional light on the important role of the surfactant adsorption layers for understanding the details of microscopic foam film drainage and stability characteristics.