Static Surface Tension Research Articles

Effect of inorganic and organic counterions on interfacial properties of oleic acid-based gemini surfactants

We studied the effect of counterion species of oleic acid-based gemini surfactants with carboxylate headgroups. Adsorption and self-aggregation properties were investigated by static surface tension, pyrene fluorescence, dynamic light scattering and phase diagram measurements. We found that, in the case of inorganic counterions (Li+, Na+, K+, and Cs+), a decreased ion size leads to a decreased critical micelle concentration (cmc) as well as a decreased area per surfactant molecule adsorbed at the air/aqueous solution interface (Acmc). The smaller inorganic counterions (hard acid) can interact with the carboxylate headgroups (hard base), and hence reduce the head-to-head electrostatic repulsion. The smaller counterions also induced the lower phase transition concentration from an optically isotropic solution (L1) phase to a hexagonal liquid crystal (H1) phase. In the case of organic counterions (monoethanolamine (MEA) and diethanolamine (DEA)), the micellization behavior was predominantly affected by the hydrophobicity of the counterions, whereas the hydrated ion size was a key parameter determining the molecular packing at the air/solution interface. In addition, we found a structural transformation from larger aggregates to smaller ones (micelles) to occur for the organic counterion systems at dilute surfactant concentrations.

Synthesis of environment friendly biosurfactants and characterization of interfacial properties for cosmetic and household products formulations

In this study, 2 types of zwitterionic phospholipid biosurfactants LP(A) and LP(O) were prepared using 2 different raw materials such as rapeseed oil and rapeseed acid respectively. The structure of the resulting products was elucidated by FT-IR, 1H NMR, and 13C NMR spectroscopies and the interfacial properties of LP(A) and LP(O) have been examined such as CMC, static and dynamic surface tensions, interfacial tension, wetting property, emulsion stability, and foam property. Detergency test evaluated by using a Terg-o-tometer showed moderately good detergency compared with conventional nonionic and anionic surfactants used in detergent formulations. Biodegradability, acute oral toxicity, acute dermal irritation and acute eye irritation tests revealed that LP(O) surfactant possesses excellent mildness and superior environmental compatibility, indicating the potential applicability in cosmetic and household products formulations.

Extraction and Characterization of Surfactants from Atmospheric Aerosols.

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in the Earth's atmosphere, a central process in meteorology, hydrology, and for the climate system. But because specific extraction and characterization of these compounds have been lacking for decades, very little is known on their identity, properties, mode of action and origins, thus preventing the full understanding of cloud formation and its potential links with the Earth's ecosystems.In this paper we present recently developed methods for 1) the targeted extraction of all the surfactants from atmospheric aerosol samples and for the determination of 2) their absolute concentrations in the aerosol phase and 3) their static surface tension curves in water, including their Critical Micelle Concentration (CMC). These methods have been validated with 9 references surfactants, including anionic, cationic and non-ionic ones. Examples of results are presented for surfactants found in fine aerosol particles (diameter <1 μm) collected at a coastal site in Croatia and suggestions for future improvements and other characterizations than those presented are discussed.

Extraction and Characterization of Surfactants from Atmospheric Aerosols

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in the Earth's atmosphere, a central process in meteorology, hydrology, and for the climate system. But because specific extraction and characterization of these compounds have been lacking for decades, very little is known on their identity, properties, mode of action and origins, thus preventing the full understanding of cloud formation and its potential links with the Earth's ecosystems. In this paper we present recently developed methods for 1) the targeted extraction of all the surfactants from atmospheric aerosol samples and for the determination of 2) their absolute concentrations in the aerosol phase and 3) their static surface tension curves in water, including their Critical Micelle Concentration (CMC). These methods have been validated with 9 references surfactants, including anionic, cationic and non-ionic ones. Examples of results are presented for surfactants found in fine aerosol particles (diameter <1 μm) collected at a coastal site in Croatia and suggestions for future improvements and other characterizations than those presented are discussed.

Dynamic surface tension measurement for the screening of biosurfactants produced by Lactobacillus plantarum subsp. plantarum PTCC 1896.

Currently, screening of microbial biosurfactants (BSs) is based on their equilibrium surface tension values obtained using static surface tension measurement. However, a good surfactant should not only have a low equilibrium surface tension, but its dynamic surface tension (DST) should also decrease rapidly with time. In this study, screening of BSs produced by Lactobacillus plantarum subsp. plantarum PTCC 1896 (probiotic) was performed based on their DST values measured by Wilhelmy plate tensiometry. The relationship between DST and structural and functional properties (anti-adhesive activity) of the BSs was investigated. The results showed that the changes in the yield, productivity and structure of the BSs were growth medium and incubation time dependent (p<0.05). Structurally different BSs produced exhibited identical equilibrium surface tension values. However, differences among the structure/yield of the BSs were observed through the measurement of their DST. The considerable dependence of DST on the concentration and composition of the BS proteins was observed (p<0.05). Moreover, the anti-adhesive activity of the BS was found to be positively correlated with its DST. The results suggest that the DST measurement could serve as an efficient method for the clever screening of BSs producer/production condition, and consequently, for the investigation of probiotic features of bacteria, since the anti-adhesive activity is an important criterion of probiotics.

Synthesis of Quaternary Ammonium Salts Based on Diketopyrrolopyrroles Skeletons and Their Applications in Copper Electroplating.

A series of DPP derivatives bearing quaternary ammonium salt centers with different lengths of carbon chains have been designed and synthesized. Their inhibition actions on copper electroplating were first investigated. A total of four diketopyrrolopyrrole (DPP) derivatives showed different inhibition capabilities on copper electroplating. To investigate interactions between metal surface and additives, we used quantum chemical calculations. Static and dynamic surface tension of four DPP derivatives had been measured, and the results showed DPP-10C (1c) with a faster-decreasing rate of dynamic surface tension among the four derivatives, which indicated higher adsorption rate of additive on the cathode surface and gives rise to stronger inhibiting effect of copper electrodeposition. Then, DPP-10C (1c) as the representative additive, was selected for the systematic study of the leveling influence during microvia filling through comprehensive electroplating tests. In addition, field-emission scanning electron microscope images and X-ray diffraction results showed the surface morphology, which indicated that addition of DPP derivative (1c) could lead a fine copper deposit and cause the preferential orientations of copper deposits to change from [220] to [111], which happened in particular at higher concentrations.

Novel succinic acid based polymeric surfactants: Synthesis and performance investigation

Abstract Three novel succinic acid based polymeric surfactants, MAPEG-OSO 3 Na (M PEG = 1000, 2000, 4000), were designed and synthesized by reaction of maleic anhydride (MA) and polyethylene glycols (PEG) of different molecular weight. Their surface activities, adsorption, spreading performances, aggregation behaviors and dispersion in aqueous solution were investigated by static/dynamic surface tension measurements, contact angle techniques, transmission electron microscope (TEM) and particle size distribution (PSD) at 25 °C. Surface tension measurement for all three surfactants are about 30 mN/m. From the results of static surface tension measurements, we could estimate the CAC/C 20 ratio, adsorption efficiency (pC 20 ), maximum surface excess concentration ( Γ max ) and minimum surface area per molecule ( A min ) at air/liquid interface. The dynamic surface tension results indicated that adsorption process of aqueous solutions at air/liquid interface is mixed diffusion-kinetic adsorption mechanism. TEM analysis of MAPEG-OSO 3 Na solutions revealed that surfactant molecules can self-assemble into spherical micelles. PSD and TEM results showed that the application prospect of these surfactants is dispersant in aqueous solution.

Characterization of O/W Emulsions Prepared by PEG-Diisostearate Amphiphilic Random Copolymer.

We have characterized an emulsion system stabilized by an amphiphilic random copolymer, methoxy polyethylene glycol-23 methacrylate/glyceryl diisostearate methacrylate copolymer (MPM-GDM). The combined results of the static surface tension and transmission electron microscopy with freeze-fracture technique (FF-TEM) suggested that this copolymer forms aggregates in aqueous solutions. The membrane emulsification method produced an oil-in-water (O/W) emulsion in the mixture of squalane, water, and MPM-GDM, where the squalane concentration was set at 10 - 60 wt% and the MPM-GDM concentration was either 1 or 5 wt%. The prepared emulsion was stable against coalescence due to the formation of an adsorption layer of MPM-GDM. Based on the FF-TEM results, it is confirmed that a relatively large island-like structure is formed on the emulsion droplet surface. Furthermore, MPM-GDM can act as a thickening agent of the continuous liquid phase, which enhances the stability against creaming. The cooperative two effects improve the stability of the emulsion system without adding co-stabilizer such as low molecularweight surfactants.

English

Agricultural spray adjuvants (ASA) are widely used in pesticide applications to enhance the effective control of pest, weed and disease. The aim of this research was to investigate the effects of ASA used in Brazil agriculture on surface tension reducing capacity and foliar spray retention on different Eucalyptus species. Static surface tension of adjuvants at concentrations of 0.001, 0.0025, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0 and 2.0% v v-1 were determined by the drop weight method. Spray retention on Eucalyptus leaves using ASA were performed at concentrations of 0; 0.005; 0.01; 0.05; 0.1; 0.5; 1.0 and 2.0% v v-1. The ASA assessed were: vegetal oil, mineral oil, spreader-sticker and a drift reducing based on soybean lecithin more propionic acid. All ASA adjuvants reduced surface tension of aqueous solutions. Heptomethyltrisiloxane (HT) provided the best performance on decrease of the surface tension reaching values below to 20 mN m-1 at concentration of 0.05% v v-1. Spray retention was influenced by Eucalyptus species, adjuvants types as well as adjuvants concentrations. The increase of ASA concentration contributed to reduce spray retention. Different characteristic of the adjuvants on spray retention was observed in different Eucalyptus leaves species. Eucalyptus grandis and Eucalyptus torelliana species showed respectively the lower and higher spray retention values. The mineral oil and vegetal oil provide the higher and HT the lower level of spray retention. Application at high spray volume must be carefully performed to avoid losses by run-off when added some ASA. Key words: Foliar retention, surfactant, application techniques, chemical control.

Tensiometric, IR- and 19f-NMR Analysis of Nafion Solutions for PEMFCs and PEMELs

In the construction of polymer electrolyte membrane fuel cells (PEMFCs) and polymer electrolyte membrane electrolyzers (PEMELs), Nafion® (sulfonated tetrafluorethylene) is used as a membrane material and as proton conductor in the porous catalysts layers of membrane electrode assemblies (MEAs). Efficiency can be increased and costs reduced by optimizing and controlling the porous catalyst layer in MEAs. It is important to understand the polymer properties, which can be achieved by using different solutions and varying concentrations of one mixture for manufacturing the dispersion. Furthermore, the findings are of particular importance for the coating process. The efficiency of the PEMFCs and PEMELs depends on the number of active centers in the porous catalyst layer. The formation of the triple phase boundary is of great importance. This can be ensured by controlling the structural properties of the dispersion. Thereby, the static and dynamic surface tensions are analyzed. Surface tension and interfacial tension are necessary for understanding the coating process and adhesion to a transfer layer. The complex system was simplified and research on the surface properties performed with an aqueous Nafion® solution in an alcohol concentration series. Hence, the only aspect that changed was the alcohol, while the dynamic surface tension was measured with a bubble pressuretensiometer (BP100, KRÜSS GmbH). The static surface tension and interfacial surface tension were carried out with a force tensiometer (K100, KRÜSS GmbH) after Wilhelmy plate respectively the duNouy Ring method. In addition the solution was analyzed by means of IR- and 19F-NMR- spectroscopy. It will be demonstrated in this contribution that the static and dynamic surface tensions differ significantly at lower alcohol concentrations in solution series with and without Nafion®. While at higher alcohol concentrations the static surface tension between both series is similar, the dynamic surface tension shows a different trend with varied bubble age. This can be explained by the interaction between alcohol and Nafion®. In accordance with the previous interface outcomes, the 19F-NMR- and IR- spectra are analyzed. According to the first results, it is also apparent that there are interactions between Nafion® and alcohol. The application of these methods provides an understanding of the interaction between the molecules in the catalyst dispersions. This information is essential for understanding the interactions between the components of catalyst dispersion during electrode manufacturing.

Adsorption behavior, spreading and thermal stability of anionic-nonionic surfactants with different ionic headgroup

The anionic-nonionic surfactants have attracted great interest due to its particular molecular structure. To compare the effect of anionic headgroup on the performance of anionic-nonionic surfactants, the adsorption behavior at air/water and oil/water interface, spreading performance and thermal stability of anionic-nonionic surfactants, sodium alkyl polyethylene oxide carboxylate (AE3C), sodium alkyl polyethylene oxide sulfate (AE3S), and sodium alkyl polyethylene oxide sulfonate (AE3SO), were investigated by surface tension, interfacial tension, contact angle techniques and thermogravimetric analysis. The results of static surface tension and interfacial tension show that the AE3C has the best interfacial activity. Adsorption process for surfactants concentration above cmc is a mixed diffusion–kinetic adsorption mechanism, and below cmc is diffusion-controlled mechanism. Spreading ability on paraffin films of the three surfactants decreases in the order AE3C>AE3S>AE3SO. The thermal stability is in the sequence of AE3C>AE3SO>AE3S.

Surface Adsorption and Micelle Formation of Polyoxyethylene-type Nonionic Surfactants in Mixtures of Water and Hydrophilic Imidazolium-type Ionic Liquid.

The interfacial properties of polyoxyethylene alkyl ether-type nonionic surfactants (CnEm) were studied in a hydrophilic room-temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), in the presence of water. These properties were assessed using static surface tension, pyrene fluorescence, and dynamic light scattering measurements. The interfacial properties were strongly dependent on the solution composition. Increased water concentration lowered the critical micelle concentration (cmc). The cmc was also affected by the lengths of both the alkyl and polyoxyethylene chains, but a greater impact was observed for the alkyl chain length. These results indicate that micellization occurs as a result of solvophobic interaction between surfactant molecules in the water/bmimBF4 mixed solutions, similar to aqueous surfactant systems. The cloud point phenomenon was observed for CnEm with a relatively low hydrophilic-lipophilic balance (HLB) value, and the relationship between the cloud point and water/bmimBF4 composition exhibited a convex upward curve. Furthermore, the mixing of bmimBF4 with water increased the surfactant solubility for water-rich compositions, suggesting that bmimBF4 acts as a chaotropic salt.

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.

Interfacial study on the interaction between hydrophobic nanoparticles and ionic surfactants

Abstract The use of hydrophobic nanoparticles to manipulate the foam stability has attracted great interests recently. In this study the interactive behavior is investigated between the hydrophobic nanoparticles with the ionic surfactants including ordinarily charged and ionic liquid ones. The concentration of nanoparticles is varied and the surfactant concentration is fixed at below the critical micelle concentration, where the air–water surface property is sensitive to the state of surfactants in the bulk solution. The static and dynamic surface tension, zeta potential and dilational viscoelasticity of the mixed solution are measured at various conditions. It is observed that both surface tension and magnitude of zeta potential increase with nanoparticle addition, suggesting that the nanoparticles are attracting surfactant monomers in competition with the air–water surface and the premicelles in the bulk solution. The dynamic changes of surface tension and dilational viscoelasticity are monitored with changes of nanoparticle concentration. The possible assembly of surfactants with nanoparticles and the consequential effect are discussed with a proposed mechanism. Understanding the interaction and synergy between hydrophobic nanoparticles with ionic surfactants, in particular ionic liquid surfactant, may shed light on the use of such nanoparticles in the industrial practices such as enhanced oil recoveries.

Effect of frothers and dodecylamine on bubble size and gas holdup in a downflow column

Bubble size and gas holdup were characterized in a two phase gas–water system in a laboratory downflow column. The effect of the cationic surfactant dodecyl amine (MW 185, HLB 10.7) and the frothers MIBC (MW 102, HLB 6.05) and polyglycol F507 (MW 425, HLB 8.63) on the bubble size and gas holdup were investigated. In addition, the effect of blends of MIBC-dodecyl amine (DDA) and F507-DDA on these parameters was assessed. The bubble Critical Coalescence Concentration (CCC) followed the order MIBC>DDA>F507. When blending the frothers with DDA at a concentration below its CCC, the frother CCC decreased and bubbles of finer size were obtained below and above the frother CCC. Static surface tension measurements of aqueous solutions with frothers and DDA as well as with frothers-DDA blends show coadsorption of DDA at the air/aqueous solution interface. The surface tension of aqueous solutions prepared with the blends decreased with the addition of DDA and varied linearly with the frother concentration within the concentration range studied. The gas holdup in the downflow column was determined by the bubble size and decreased with the bubble size. It is shown that frother-DDA blends gave the lowest gas holdup in the downflow column. This work is relevant for the reverse flotation of quartz from iron ores using amine collectors in cells with downflow systems.

Physicochemical and microemulsion properties of dimeric quaternary ammonium salts with trimethylene spacer for enhanced oil recovery

Dimeric surfactants, also termed as Gemini surfactants, are regarded as organic materials which have two hydrophilic head groups and two hydrophobic groups in the molecules linked together with a spacer. In this study, dimeric surfactants of quaternary ammonium bromide connected with a trimethylene spacer group (m-3-m) have been investigated as potential micellar solutions for enhanced oil recovery. Static surface tension, interfacial tension as well as optimal salinity characterized their physicochemical and microemulsion properties. Using modeled petroleum fluids, the critical micelle concentration (CMC) was found dependent not only of the chemical architecture of the surfactant but also of the composition in the liquid phase. The nature and/or the length of spacer group participates significantly to the spatial rearrangement of the dimeric surfactants which subsequently altered the surface properties. For the same spacer group, an ultralow interfacial tension was achieved. Encouraging oil solubilization was found for surfactants used with an effect pronounced for longer alkyl chain. Furthermore, both the effects and the presence of metallic divalent ions on the phase behavior were discussed.

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.

Characterization of air/water interface adsorption of a series of partially fluorinated/hydrogenated quaternary ammonium salts

Abstract The adsorption at air/water interface of a series of partially fluorinated/hydrogenated quaternary ammonium salts was characterized by the determination of static and dynamic surface tension, critical micelle concentration, surface excess, area per molecule and Krafft temperature. In particular, the variation of these parameters was studied as a function of fluorinated and hydrogenated chain length. Modification of fluorinated and hydrogenated moieties allows to finely tune all the aforementioned physical surface properties: increasing the number of fluorinated carbon atoms boosts both effectiveness and efficiency of surfactant in reducing surface tension, kinetics of migration to interface are favored fastening reaching of equilibrium conditions, critical micelle concentration is reduced and surface excess is increased. Conversely increasing the length of the hydrogenated moiety reduces both effectiveness and efficiency of surfactant, migration to interface is slackened, c.m.c. is increased, and surface excess is depresses. Area per molecule and Krafft temperature appear to be affected mainly by the total number of carbon atoms introduced in the molecules whatever the nature of the substituent (fluorine or hydrogen).

Influence of guanidine hydrochloride and urea on the dynamic surface properties of lysozyme solutions

Guanidine hydrochloride and urea have different effects on the surface properties of lysozyme solutions due to different interaction mechanisms between the protein and denaturants: an increase in the guanidine hydrochloride concentration leads to noticeable changes in the dynamic surface elasticity, while the main effect of urea consists in a significant drop of the static surface tension.

Tetrasiloxane room temperature ionic liquids: adsorption and aggregation properties in aqueous solution

The adsorption and aggregation behavior of three tetrasiloxane surface active room temperature ionic liquids, N-(2-aminoethyl)-3-aminopropyltetrasiloxane carboxylic acid ammonium, [Si(4)N(2)-2CA(n) (n = 1, 2, 3)], have been studied on the basis of static/dynamic surface tension, conductivity, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The static surface tension of the Si(4)N(2)-2CA(n) aqueous solutions measured at the critical aggregation concentration (CAC) is observed to be significantly lower than that of amide-functionalized ILs and is comparable to those reported for trisiloxane RT-SAILs, N-(2-aminoethyl)-3-aminopropyltrisiloxane carboxylic acid ammonium and 3-aminopropyltrisiloxane carboxylic acid ammonium. The dynamic surface tension results indicate that adsorption process is a mixed diffusion-kinetic adsorption mechanism. DLS and TEM analysis of Si(4)N(2)-2CA(n) solutions reveal that they can self-assemble into vesicles with an average diameter in the range of 70–500 nm.