Dynamic Surface Tension Measurements Research Articles

Synthesis and properties of a branched short-alkyl polyoxyethylene ether alcohol sulfate surfactant

A branched alkyl polyoxyethylene ether alcohol sulfate, sodium isooctyl polyoxyethylene ether sulfate (i-OE3S), was synthesized and its physic-chemical properties were investigated systematically. The experiment on Krafft point gave a result that the Krafft temperature of i-OE3S was below 0°C. The measurement of static surface tension showed that the critical micelle concentration (cmc) and surface tension at cmc (γcmc) of i-OE3S were 21.67mmol·L−1 and 27.4mN·m−1, respectively. From the results of dynamic surface tension (DST) measurements, we could obtain that the adsorption of i-OE3S at air/liquid interface is controlled by the mixed diffusion–kinetic mechanism. Spherical assemblies with a diameter in the range of 263 to 606nm in water were observed by transmission electron microscopy (TEM). The spreading performance of i-OE3S aqueous solution on paraffin film was investigated by dynamic contact angle and the results demonstrated that i-OE3S possessed an excellent spreading ability.

Atypical wetting behaviour of alcohol–water mixtures on hydrophobic surfaces

Abstract Methanol, ethanol, n -propanol and their aqueous solutions are widely used in many industrial applications where wettability is one of the most important parameters. This project was focused on the experimental study of the wetting behaviour of these mixtures on two similar hydrophobic surfaces in the full concentration range. Based on the measurements of dynamic surface tension and dynamic liquid drop spreading we proved the stable composition of liquid layers on the solid–liquid and liquid–air interfaces. Likewise, in bulk liquid the existence of small aggregates consisting of water and alcohol molecules is assumed. This complex internal structure of aqueous solutions of short chain alcohols influences the surface properties of these solutions and explains the higher contact angles when compared to pure liquids with similar surface tension.

Stabilizing and destabilizing protein surfactant-based foams in the presence of a chemical surfactant: Effect of adsorption kinetics

Stimuli-responsive protein surfactants promise alternative foaming materials that can be made from renewable sources. However, the cost of protein surfactants is still higher than their chemical counterparts. In order to reduce the required amount of protein surfactant for foaming, we investigated the foaming and adsorption properties of the protein surfactant, DAMP4, with addition of low concentrations of the chemical surfactant sodium dodecylsulfate (SDS). The results show that the small addition of SDS can enhance foaming functions of DAMP4 at a lowered protein concentration. Dynamic surface tension measurements suggest that there is a synergy between DAMP4 and SDS which enhances adsorption kinetics of DAMP4 at the initial stage of adsorption (first 60s), which in turn stabilizes protein foams. Further interfacial properties were revealed by X-ray reflectometry measurements, showing that there is a re-arrangement of adsorbed protein–surfactant layer over a long period of 1h. Importantly, the foaming switchability of DAMP4 by metal ions is not affected by the presence of SDS, and foams can be switched off by the addition of zinc ions at permissive pH. This work provides fundamental knowledge to guide formulation using a mixture of protein and chemical surfactants towards a high performance of foaming at a low cost.

New Dynamic-Surface-Tension Analysis Yields Improved Residual Surfactant Measurements in Flowback and Produced Waters

Summary Surfactant is a significant component within fracturing-fluid additives that is used for enhancing oil and gas production following stimulation of unconventional reservoirs. To help ensure optimal applications of surfactants, operating and service companies have been searching for tools for tracking surfactant residuals in flowback and produced waters, which possibly can be correlated with well productivity. This paper discusses the residual surfactant concentration measured in produced water from example Barnett shale formation wells by use of a dynamic surface tension (DST) technique, which yields much more accurate measurements. DST measurement by maximum bubble-pressure technique is well-known, but it has not been used explicitly for the application of residual surfactant measurement in produced water. A comparison of DST includes evaluating the diffusion coefficient to the reaction kinetics of adsorption of a known molecule(s) in produced water. Short-time kinetics of adsorption of different molecules vary on the basis of chemical nature and molecular size. Ultraviolet–visible (UV–Vis) spectroscopy is used to confirm the results. An estimate of residual concentrations from UV–Vis appears to be coherent with DST-measurement values. Such measurements can be useful in determining the surfactant concentration during pumping and the surfactant performance during and after hydraulic-fracturing operations. Additionally, these measurements serve a vital role in tailoring the surfactant additive to specific reservoir conditions to achieve higher oil recovery. Real-time production results from these different wells are analyzed and appear dependent on the corresponding residual surfactant concentrations from produced waters. This unique technique is new to the authors’ knowledge for its use to study and analyze produced water for surfactant-additive concentration.

Static and dynamic surface tension behaviour of a triblock copolymer and a non ionic surfactant mixture

Abstract Static and dynamic surface tension measurements have been carried out on mixtures of a commonly used block copolymer Pluronics ® P123 and a non-ionic surfactant polyoxyethelene (9) lauryl ether (C 12 E 9 ) to understand the block polymer-surfactant interactions. The effects of the interaction on the adsorption and micellisation behaviour have also been studied. Three different compositions comprising 3:1, 1:1 and 1:3 molar ratios of Pluronic P123 and C 12 E 9 have been investigated and the results are compared with the data of pure P123 and C 12 E 9 solutions. It has been observed that the nature and magnitude of the polymer surfactant interactions depend on the composition of the mixtures. The mixture containing 3:1 molar ratio of P123 and C 12 E 9 shows synergistic effect with a negative value for the interaction parameter (β), as obtained from the analysis of surface tension data using Rubingh’s model. However, for the other two compositions (i.e., 1:1 and 1:3 molar ratios), the equilibrium surface tension data show premicellar adsorption and aggregation of the surfactant molecules on the polymer chain. The dynamic surface tension (DST) results indicate that the strong polymer surfactant interactions, as reflected in the equilibrium surface tension data, do not modify the DST behaviour significantly from that of pure components. This is attributed to the dominant effect of the polymer adsorption at the interface, during the short time scale studied.

Simplified process for preparation of schizophyllan solutions for biomaterial applications

ABSTRACTSchizophyllan is a biopolymer commercially produced for pharmaceutical and cosmetics uses. However, schizophyllan also has potential biomaterial applications. Schizophyllan is conventionally produced from glucose and recovered by diafiltration and ultrafiltration to produce a highly purified product. Here we demonstrate a simplified process for preparation of schizophyllan solutions for biomaterial applications. Schizophyllan was produced in 1.5-L bioreactors from distiller’s dried grains with solubles (DDGS), an abundant coproduct of dry grind fuel ethanol production. Downstream processing eliminated filtration and concentration steps, providing solutions containing 4.2 ± 0.3 g schizophyllan/L. Solutions contained high-molecular-weight schizophyllan and exhibited viscosity properties similar to those of commercial schizophyllan. Schizophyllan solutions showed promise as a component of biolubricants in friction and wear tests and by dynamic surface and interfacial tension measurements.

Surface tension in human pathophysiology and its application as a medical diagnostic tool.

Introduction: Pathological features of disease appear to be quite different. Despite this diversity, the common feature of various disorders underlies physicochemical and biochemical factors such as surface tension. Human biological fluids comprise various proteins and phospholipids which are capable of adsorption at fluid interfaces and play a vital role in the physiological function of human organs. Surface tension of body fluids correlates directly to the development of pathological states. Methods: In this review, the variety of human diseases mediated by the surface tension changes of biological phenomena and the failure of biological fluids to remain in their native state are discussed. Results: Dynamic surface tension measurements of human biological fluids depend on various parameters such as sex, age and changes during pregnancy or certain disease. It is expected that studies of surface tension behavior of human biological fluids will provide additional information and might become useful in medical practice. Theoretical background on surface tension measurement and surface tension values of reference fluids obtained from healthy and sick patients are depicted. Conclusion: It is well accepted that no single biomarker will be effective in clinical diagnosis. The surface tension measurement combined with routine lab tests may be a novel non-invasive method which can not only facilitate the discovery of diagnostic models for various diseases and its severity, but also be a useful tool for monitoring treatment efficacy. We therefore expect that studies of surface tension behavior of human biological fluids will provide additional useful information in medical practice.

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.

Climate-relevant physical properties of molecular constituents for isoprene-derived secondary organic aerosol material

Abstract. Secondary organic aerosol (SOA) particles, formed from gas-phase biogenic volatile organic compounds (BVOCs), contribute large uncertainties to the radiative forcing that is associated with aerosols in the climate system. Reactive uptake of surface-active organic oxidation products of BVOCs at the gas–aerosol interface can potentially decrease the overall aerosol surface tension and therefore influence their propensity to act as cloud condensation nuclei (CCN). Here, we synthesize and measure some climate-relevant physical properties of SOA particle constituents consisting of the isoprene oxidation products α-, δ-, and cis- and trans-β-IEPOX (isoprene epoxide), as well as syn- and anti-2-methyltetraol. Following viscosity measurements, we use octanol–water partition coefficients to quantify the relative hydrophobicity of the oxidation products while dynamic surface tension measurements indicate that aqueous solutions of α- and trans-β-IEPOX exhibit significant surface tension depression. We hypothesize that the surface activity of these compounds may enhance aerosol CCN activity, and that trans-β-IEPOX may be highly relevant for surface chemistry of aerosol particles relative to other IEPOX isomers.

Adsorption of oat proteins to air–water interface in relation to their colloidal state

The colloidal size and charge of oat protein isolate (OPI) at pH 7.2 and 9.0 with/without transglutaminase (TG) treatment were investigated and related to its surface activity at air–water interface. OPI was prepared from defatted oat flour. It was dispersed in water (pH 7.2), or in buffer (pH 9.0) and the soluble fraction (supernatant after centrifugation at 10 000 × g) was used for particle size, ζ-potential and dynamic surface tension measurements. Dispersions were found to be electrostatically stable (ζ-potential > −35 mV) with average particle sizes of ∼70 nm at pH 7.2 and ∼30 nm at pH 9.0. When diluted at pH 7.2, dissociation and re-association of the particles occurred resulting in increased polydispersity and increased size, while at pH 9.0 particle size and ζ-potential were unchanged after dilution. Dynamic surface tension measurements revealed slower adsorption dynamics and higher final surface tension values at pH 9.0 than at pH 7.2. TG-treatment of OPI dispersion resulted in formation of inter-molecular covalent linkages and led to decreased average particle size and increased stability against dilution in OPI dispersions at neutral pH. TG-treated proteins showed increased negative charge at pH 7.2 and resulted in higher surface tension values compared to the untreated samples. The topography images of adsorbed or spread layers of OPI at a/w interface revealed that oat globulins were effectively adsorbed and existed as monomeric particles or formed aggregates at the interface depending on pH.

Dynamic surface tension measurement with temporal resolution on microsecond scale

We introduce a method for measuring the time-dependent surface tension of liquid with a time resolution higher than 0.1 ms. The method involves inkjet technology with in-flight manipulation of droplets. Droplets are launched continuously and then deformed by a dielectric force. The resonance oscillation of droplets after deformation is observed, and eigenfrequencies for given droplet radii indicate the surface tension as a function of time after the formation of a liquid surface. We demonstrate experimental results for the cases of water and an aqueous solution containing surfactant material, in which constant and time-dependent surface tension are expected, respectively.

Adsorption and thermodynamics of biosurfactant, surfactin, monolayers at the air-buffered liquid interface

Adsorption of surfactin, a powerful lipopeptide biosurfactant, at the air-liquid interface has been investigated in this article. The adsorption took place from buffered solutions containing relatively high concentrations of surfactin co- and counterions. Dynamic surface tension measurements were used to follow the self-assembly of surfactin at the interface until equilibrium surface pressure Π e is reached at a given surfactin concentration (C s). Gibbs adsorption equation in conjunction with the Langmuir adsorption isotherm was used to predict surfactin surface excess as a function of the biosurfactant concentration up to the critical micelle concentration (CMC). The predicted surface excess at saturation (Γ ∞ ) is 1.05 ± 0.05 μmol m−2, corresponding to an area per molecule (A ∞ ) of 159 ± 8 A2. The adsorption equilibrium constant (K = (1.5 ± 0.6) × 106 M‐ 1) was also estimated from the nonlinear regression of Π e − C s data in region B of the Π e − ln C s plot. The value of K suggests that surfactin has strong affinity for the interface, which is in line with its known high surface activity. Gibbs elasticity (E G) of the interfacial surfactin monolayers, which is an important thermodynamic property, was also predicted at different surfactin concentrations. The limiting value (at the CMC) of E G was found to be 183 mN m−1, which is comparable to those reported in the literature for similar systems. The findings reported in this work reveal that the surface tension measurements coupled with appropriate theoretical analysis could provide useful information comparable to those obtained using highly sophisticated techniques.

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.

Adsorption properties of biologically active derivatives of quaternary ammonium surfactants and their mixtures at aqueous/air interface II. Dynamics of adsorption, micelles dissociation and cytotoxicity of QDLS

The main aim of our study was analysis of adsorption dynamics of mixtures containing quaternary derivatives of lysosomotropic substance (QDLS). Two types of equimolar mixtures were considered: the ones containing two derivatives of lysosomotropic substances (DMALM-12 and DMGM-12) as well as the catanionic mixtures i.e. the systems containing QDLS and DBSNa. Dynamic surface tension measurements of surfactant mixtures were made. The results suggested that the diffusivity of the mixed system could be treated as the average value of rates of diffusion of individual components, micelles and ion pairs, which are present in the mixtures studied. Moreover, an attempt was made to explain the influence of the presence of micelles in the mixtures on their adsorption dynamics. The compounds examined show interesting biological properties which can be useful, especially for drug delivery in medical treatment. In vitro cytotoxic activities of the mixtures studied towards human cancer cells were evaluated. Most of the mixtures showed a high antiproliferative potential, especially the ones containing DMALM-12. Each cancer cell line used demonstrated different sensitivity to the same dose of the mixtures tested.

Measurement of dynamic surface tension using helical flow of a viscous liquid in a pool of another viscous liquid inside a micro-channel

Measurement of surface tension (s.t.) and critical micelle concentration (c.m.c.) of a surfactant in dynamic condition is important for several engineering applications, for which, the interface between two or more different phases does not remain constant but alters and replenishes continuously with flow of the fluids so that equilibrium may not be reached between the bulk and the interface. There are however not many methods for measuring these quantities in dynamic experiments which mimics the real dynamic situations. In this report, we present a novel two-phase flow pattern inside a triple-helical micro-channel using which, we show that it may be possible to measure the dynamic s.t. of a liquid. When two immiscible liquids such as oil and water are pumped into it, at a certain range of flow rates, oil flows as the continuous phase, whereas water remains in it as a wavy filament, the wavelength of which varies with the flow rates of oil and water but also on the interfacial tension between these two liquids. We show that wavelength decreases with increase in concentration of a solute attaining a minima at the c.m.c. A simple scaling analysis captures most experimental observations.

Determination of the Stabilization Time of the Solution-Air Interface for Aggregates Formed by NaC in Mixtures with SDS and PEO, Investigated by Dynamic Surface Tension Measurements

The properties of mixtures of poly (ethylene oxide) (PEO) and mixed micelles formed from sodium cholate (NaC) and sodium dodecyl sulfate (SDS) in tris/HCl buffered solutions at pH 9.00 were investigated by measuring the mean surface tension. The variation in the superficial tension as a function of the time after formation of solutions containing PEO and NaC was characterized by monitoring the time required for the system to reach equilibrium between the micellar and aqueous phases. These results could serve as a reference for the minimum aging time required for solutions before any surface tension measurements can be performed.

Characterization of highly substituted, cationic amphiphilic starch derivatives: Dynamic surface tension and intrinsic viscosity

The surface activity and viscometric behavior of highly substituted, amphiphilic polysaccharides, derived from potato starch by modification with benzyl- and hydroxypropyl-trimethylammonium groups, are studied in salt-free and 0.05 M NaCl aqueous solution. For the first time dynamic surface tension measurements of amphiphilic starch derivatives have been effected using the pendant drop method and it was possible to correlate them with particle sizes and apparent charge density. Rheological investigation of large concentration ranges (0.01–20 g/L) is used to discuss Huggins plots and typical polyelectrolyte (PEL) behavior for all starch derivative samples could be found. The determination of overlap concentration and, in dilute aqueous solution, of intrinsic viscosity was possible. For the latter one the semi-empirical equation of Rao was used, making it possible to get insights to PEL conformation in dependence on the degrees of substitution (DS) of both substituents. It is shown that for intrinsic viscosity an inversion of the impact of both substituents takes place, with hydrophobic benzyl groups on the one hand and cationic hydroxypropyl-trimethylammonium groups on the other. Data evaluation via the ratio of both DS values had been successfully utilized and thus, the applied method has been identified as being a promising tool to compare a multitude of starch derivatives with substituents of different polarity in various DS to get tendencies regarding overall hydrophobicity.

Aqueous solutions of the double chain cationic surfactants didodecyldimethylammonium bromide and ditetradecyldimethylammonium bromide with Pluronic F68: Dynamic surface tension measurements

The adsorption kinetics of mixtures of the non-ionic copolymer Pluronic F68 with two double chain cationic surfactants didodecyldimethylammonium bromide (di-DDAB) and ditetradecyldimethylammonium bromide (di-TDAB) is studied with dynamic surface tension experiments. A time dependent synergy is observed, in most of the mixtures. In a few cases, hindrance effects are observed. Clusters are formed at concentrations well below the critical micelle concentration (cmc), at the critical aggregation concentration (cac). The presence of the copolymer stabilizes the electrostatic repulsion between the positively charged quaternary ammonium headgroups of di-DDAB and di-TDAB. The electrostatic repulsion between the polar parts of the same and adjacent surfactant molecules is minimized. We compare our results with recently published results, using mixtures of these double chain cationic surfactants with hydroxypropylmethylcellulose.

Adsorption behavior of non-conventional eco-friendly tyrosine glycerol ether surfactants

Due to the increasing demand for environmentally friendly surfactants, a novel non-conventional glycerol ether surfactant with 12 carbon atoms in the hydrophobic alkyl chain and the amino acid tyrosine in the hydrophilic head (TyrGE12) is synthesized. Measurements of dynamic surface tension by maximum bubble pressure tensiometry and drop profile tensiometry are carried out for alkali aqueous solutions over a wide concentration range and for surface ages spanning from milliseconds to hours. Critical Micelle Concentration (CMC) value, standard free energy of adsorption and other physicochemical properties are calculated based on static (equilibrium) surface tension measurements. Dynamic surface tension data are analyzed using approximate solutions of the Ward and Tordai model to estimate diffusion coefficients for short and long adsorption times. For concentrations above the CMC, the effective diffusion coefficient (D*) of monomers is also estimated. Diffusion coefficients for short adsorption times lie in a physically reasonable range whereas for long adsorption times the computed very low values indicate the presence of an adsorption barrier. Interfacial dilatational storage modulus and loss modulus measurements indicate a dominant elastic character of the adsorption layer for all the examined concentrations and oscillation frequencies. Local peaks in the values of both moduli, below and above CMC, imply that structural changes in the adsorption layer might be partially affected by the presence of micelles.

Equilibrium Surface Tension, Dynamic Surface Tension, and Micellization Properties of Lactobionamide-Type Sugar-Based Gemini Surfactants

A sugar-based gemini surfactant N,N'-dialkyl-N,N'-dilactobionamideethylenediamine (2C(n)Lac, where n represents alkyl chain lengths of 8, 10, 12, and 14) was synthesized by reacting N,N'-dialkylethylenediamine with lactobionic acid. The adsorption properties of 2C(n)Lac were characterized by equilibrium and dynamic surface tension measurements. Their micellization properties were investigated by steady-state fluorescence using pyrene as a probe and dynamic light scattering (DLS) techniques. The dependence of these properties on the alkyl chain length and the number of sugars was determined through a comparison with the corresponding monomeric surfactants C(n)MLA and previously reported sugar-based gemini surfactants containing monosaccharide gluconamide or disaccharide lactobionamide groups with a hexanediamide spacer. The critical micelle concentration (cmc) and surface tension of 2C(n)Lac are both lower than those of C(n)MLA surfactants. These lower values indicate that the synthesized sugar-based gemini surfactants have excellent micelle-forming ability in solution and high adsorption ability at the air-water interface, which result from strong interactions of the hydrogen bonds between the hydroxyls in lactobionamide groups. When the alkyl chain length of 2C(n)Lac increases to 14, premicellar formation occurs in the solution along with adsorption at the air-water interface at concentrations below the cmc. Furthermore, 2C(n)Lac forms micelles measuring 4 to 12 nm in solution, with no dependence on the alkyl chain length, and their size slightly increases with increasing concentration.