Effect of anionic surfactant and short-chain alcohol mixtures on adsorption at quartz/water and water/air interfaces and the wettability of quartz

Measurements of the advancing contact angles for aqueous solutions of sodium dodecyl sulfate (SDDS) or sodium hexadecyl sulfonate (SHS) in mixtures with methanol, ethanol, or propanol on a quartz surface were carried out. On the basis of the obtained results and Young and Gibbs equations the critical surface tension of quartz wetting, the composition of the surface layer at the quartz-water interface, and the activity coefficients of the anionic surfactants and alcohols in this layer as well as the work of adhesion of aqueous solutions of anionic surfactant and alcohol mixtures to the quartz surface were determined. The analysis of the contact angle data showed that the wettability of quartz changed visibly only in the range of alcohol and anionic surfactant concentration at which these surface-active agents were present in the solution in the monomeric form. The analysis also showed that there was a linear dependence between the adhesion and the surface tension of aqueous solutions of anionic surfactant and alcohol mixtures. This dependence can be described by linear equations for which the constants depend on the anionic surfactant and alcohol concentrations. The slope of all linear dependence between adhesion and surface tension was positive. The critical surface tension of quartz wetting determined from this dependence by extrapolating the adhesion tension to the value equal to the surface tension (for contact angle equal zero) depends on the assumption whether the concentration of anionic surfactant or alcohol was constant. Its average value is equal to 29.95mN/m and it is considerably lower than the quartz surface tension. The positive slope of the adhesion-surface tension curves was explained by the possibility of the presence of liquid vapor film beyond the solution drop which settled on the quartz surface and the adsorption of surface-active agents at the quartz/monolayer water film-water interface. This conclusion was confirmed by the work of adhesion of aqueous solutions of anionic surfactants and short-chain alcohol mixtures to the quartz surface determined on the basis of the contact angle data and molar fraction of anionic surfactants and alcohols and their activity coefficient in the surface layer.     

Controlling hydrolysis and dispersion of AlN powders in aqueous media

Aqueous suspensions of aluminum nitride (AlN) powders have been prepared in the presence of different surface-active agents, namely, H3PO4 and an anionic surfactant, to avoid the hydrolysis of AlN powders and to enhance dispersion. The most determinant parameters to the hydrolysis process (DeltapH and time of contact) and the stabilization of AlN particles in water (surface crystallinity, surface chemical modification, and surface ionic charge) were seen to be strongly dependent on the acidic agent. The H3PO4 treatment was effective against hydrolysis of AlN due to the formation of a phosphate-based protection layer on the particles' surface, and, although it keeps the pH of the suspension below 4, it does not guarantee a good dispersion. The individual adsorption of the anionic surfactant at the surface of AlN particles suspensions did not completely suppress the hydrolysis but it did enhance the degree of dispersion. A proper combination of the two types of surface-active agents enabled the preparation of AlN aqueous suspensions of relatively low viscosity and high AlN concentration, which can be a good starting point for aqueous-based colloidal shaping techniques or for freeze granulation or spray drying to obtain suitable granulate powder characteristics for dry-pressing technologies. An adsorption mechanism of the surface-active agents onto the particles' surface is proposed and supported by NMR and FT-IR analyses.     

Surface properties of mixtures of surface-active sugar derivatives with ionic surfactants: theoretical and experimental investigations

Surface properties of systems that are mixtures of ionic surfactants and sugar derivatives-anionic surfactant sodium dodecyl sulfate and n-dodecyl-beta-D-maltoside (SDS/DM) and cationic surfactant dodecyltrimethylammonium bromide and n-dodecyl-beta-D-glucoside (DTABr/DG)-were investigated. The experimental results obtained from measurements of surface tension of mixtures with various ratio of ionic to nonionic components were analyzed by two independent theories. First is Motomura theory, derived from the Gibbs-Duhem equation, allowing for indirect evaluation of the composition of mixed monolayers and the Gibbs energies of adsorption, corresponding to mutual interaction between surfactants in mixed adsorbed film. As second theory we used our newly developed theoretical model of adsorption of ionic-nonionic surfactant mixtures. Using this approach, we were able to describe the experimental surface tension isotherms for mixtures of surface-active sugar derivatives and ionic surfactants. We obtained a good agreement with experimental data using the same set of model parameters for a whole range of studied compositions of a given surfactant mixture. The values of surface excess calculated from both theories agreed with each other with a reasonable accuracy. However, the newly developed model of adsorption of ionic-nonionic surfactant mixtures has the advantage of straightforward determination of surface layer composition. By the solution of equations of adsorption, one can obtain directly the values of surface excess of all components (surfactant ions, counterions, and nonionic surfactants molecules), which are present in the investigated system.     

NaBr对杂双子表面活性剂C_mOhpNC_8水溶液吸附和聚集的影响

以表面张力和荧光探针技术研究了NaBr对杂双子表面活性剂CmOhpNC8(m:10,14,16)水溶液性质的影响。结果表明,NaBr强烈促进了CmOhpNC8在气/液界面上的吸附和在水相中的聚集,其中c20在cNaBr≥10mmol/L时降到极低的微摩尔/升数量级,显示了相当高的降低水表面张力效率。在NaBr促进下,水溶液中CmOhpNC8表现出强烈的预胶团化行为。这些均是对应的2种单头基单烷烃链表面活性剂简单1:1混合所无法实现的,显示了在头基处引入短联接链形成杂双子结构的表面活性优势以及对盐效应的敏感性。     

Surface activity of amphiphiles in hydrogen fluoride — water solutions

Surface tension measurements were carried out in surfactant — hydrofluoric acid — water systems and surfactant — anhydrous hydrofluoric acid systems. Surface tension measurements show that surfactants in anhydrous hydrofluoric acid do not effect a detectable change in surface tension. Effects, known from other solvents, can only be observed when water addition takes place. The surface tension lowering, the free standard adsorption energy, and the maximum surface concentration of a surfactant increases with decreasing hydrofluoric acid concentrations. The space requirement of a separate surfactant molecule decreases at the phase border with decreasing hydrofluoric acid concentrations of the solvents. Simultaneously, the CMC values were changed to smaller surfactant concentrations.     

A model for simulating the dynamic surface tension behavior of aqueous surfactant dispersions

A dynamic adsorption model for surface-active materials at air/liquid interfaces with the consideration of aggregate dissolution effect was developed to investigate the dynamic surface tension behavior of aqueous surfactant dispersions. Two catanionic surfactants, cetylpyridinium dodecylsulfate (CP-DS) and dodecyltrimethylammonium dodecylsulfate (DTMA-DS), with low critical aggregation concentrations were chosen as model systems. Dynamic surface tensions of aqueous CP-DS and DTMA-DS systems were measured by a drop volume tensiometer. A model with diffusion-controlled or mixed-kinetic dynamic adsorption mechanisms considering the dissolution effect of dispersed aggregates was developed to simulate the dynamic surface tension data. An analysis by comparing the model predictions with experimental data demonstrated that the dynamic surface tension behavior of aqueous CP-DS and DTMA-DS dispersions could be described with a diffusion-controlled dynamic adsorption model taking the aggregate dissolution effect into account.     

Mixed micelle formation in aqueous solutions of nonyl-N-methylglucamine with sodium perfluorooctanoate at different pressures

For the mixed system of nonyl-N-methylglucamine (MEGA9) with sodium perfluorooctanoate (SPFO), the critical micelle concentrations (CMC) at atmosphreic pressure and 30°C were determined from measurement of surface tension, and those at high pressures were determined by the electroconductivity method at mole fractions of MEGA9 up to 0.6. All of MEGA9-SPFO mixed systems have been found to have a surface activity much greater than the respective pure systems, i.e., a synergism of surface activity caused by mixing MEGA9 and SPFO. The mixing reduces the pressure dependence of the CMC. This suggests that this combination is useful when it is desirable for a surfactant solution to be independent of pressure. The composition of the mixed micellar phase has been estimated by applying the Motomura equation. The Gibbs energy of the mixed micelle formation has also been calculated as a function of mole fraction of a surfactant in the surfactant mixture.To whom correspondence should be addressed.     

Tensiometric study of surface activity and halothane impact on biosurfactant production of lung cells

Alveolar pneumocytes type II produce in vivo surface-active components, called lung surfactant (LS), which functions at the alveolar air/water interface are very important for the lung mechanics. LS exists in vivo as a colloid-dispersed phospholipid system and its deficiency or inactivation caused by inhalation toxins leads to severe respiratory problems, which are widely studied from the point of view of surface and colloid chemistry, biophysics, biochemistry and medicine.

In this work we investigated the biosurfactant (phospholipids) production by A 549 cells (which originate from the alveolar pneumocytes type II) by measuring the decrease of surface tension in the medium where the cells were grown. Also we studied the effects of halothane on the surfactant production, its accumulation in the cell culture medium and the cell adhesive properties.

Our results showed that there was significant increase of the phospholipid content in the cell culture medium and its surface activity during time of cell growth, detected by surface tension measurements. It was shown that the equilibrium surface tension values of the medium with cells decreased with ca. 4.5 mN/m at 24 h and with 12.0 mN/m at 48 h in comparison with the medium without cells. The effects of halothane on the surfactant production and cell adhesive properties were proved to be time- and concentration-dependent.

Our results demonstrate the opportunity of the interfacial tensiometry to monitor the production of biosurfactants in the field of cell culturing and in colloid systems where biosurfactants exist in vivo and that the tensiometric measurements have potential for use as diagnostic tools in medical applications.     

Control of surfactant level in starve-fed emulsion polymerization. I. Sulfate-containing oligomers: Preparation and application as surfactant in emulsion polymerization

It is well known that the amount of surfactant must be carefully controlled during starve-fed emulsion polymerization processes. Too little surfactant leads to emulsion instability and coagulation, while too much surfactant leads to secondary particle formation. Although these relationships are qualitatively understood in the art, there is little quantitative basis to guide the synthetic chemist, especially in multistep starve-fed emulsion polymerization processes to make larger supermicron particles. We have developed a method, which will be described in a companion article, to control the surfactant level by monitoring the surface tension during polymerization. In order to quantitatively predict how much surfactant to add at any given time, one needs to know in advance the adsorption characteristics of the soap. Further complicating the matter is the formation of “in situ” or oligomeric surfactant during polymerization with aqueous initiators such as ammonium persulfate. This work demonstrates how to prepare surface-active oligomers and how to make latex particles using them as surfactant. First, we established the mass balance for the initiator-derived sulfate groups in seed latexes by conductometric, potentiometric, and iodometric titrations. Based on the characterization of seed latexes, a method for determining the effective sulfate concentration has been developed. When surface-active oligomers were used as the only surfactant, we obtained a series of monodisperse, supermicron copolymer latex particles with diameters up to 3.22 μm. This is a similar result to that obtained with a commercially made anionic surfactant. © 1995 John Wiley & Sons, Inc.     

Thermally cleavable surfactants based on furan-maleimide Diels-Alder adducts

Two new surfactant molecules are reported that contain thermally labile Diels-Alder adducts connecting the hydrophilic and hydrophobic sections of each molecule. The two surfactants possess identical hydrophobic dodecyl tail segments but have phenol and carboxylic acid hydrophilic headgroups, respectively. Deprotonation with potassium hydroxide affords the formation of water-soluble surfactants. Room temperature aqueous solutions of both surfactants exhibit classical surface-active agent behavior similar to common analagous alkylaryl surfactant molecules. Critical micelle concentrations have been determined for each surfactant through dynamic surface tension and dye solubilization techniques. Small-angle neutron scattering measurements of the aqueous surfactant solutions indicate the presence of spherical micelles with radii of 16.5 angstroms for the carboxylate and 18.8 angstroms for the phenolate. When these surfactants are exposed to elevated temperatures (>50 degrees C), the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments. Aqueous solutions of each surfactant subsequently exhibit a loss of all surface-active behavior and the micellar aggregates are no longer detectable.     

一种新型表面活性剂的表面活性的研究

采用表面张力法确定了新型表面活性剂3-对壬基苯氧基-2-羟丙基三甲基溴化 铵的临界胶束浓度(cmc)，并考察了盐度、温度和pH值对其cmc的影响。结果表明， 此种表面活性剂的表面活性较高，盐度对其cmc影响最大，其次是pH值，温度对其 cmc的影响较为复杂。理论计算结果表明，采用热力学函数可较好地解释试验结果 。     

Novel Peroxide Containing Maleinate Surface-Active Monomers for Obtaining Reactive Polymers

Novel surface-active monomers were synthesized by successive treatment of tert-butylperoxy-6-hydroxyhexanoate with maleic anhydride, 1,3-propane sultone and triethylamine or with maleic anhydride and poly(ethylene glycol) methyl ether. The surface-active properties of monomers were studied. The critical micelle concentrations (cmc) as well as the surface tension at the cmc were determined for obtained monomers. The synthesized compounds were shown to be suitable reactive surfactants for obtaining styrene latexes.     

Lung surfactant dysfunction in tuberculosis: effect of mycobacterial tubercular lipids on dipalmitoylphosphatidylcholine surface activity

In pulmonary tuberculosis, Mycobacterium tuberculosis bacteria reside in the alveoli and are in close proximity with the alveolar surfactant. Mycolic acid in its free form and as cord factor, constitute the major lipids of the mycobacterial cell wall. They can detach from the bacteria easily and are known to be moderately surface active. We hypothesize that these surface-active mycobacterial cell wall lipids could interact with the pulmonary surfactant and result in lung surfactant dysfunction. In this study, the major phospholipid of the lung surfactant, dipalmitoylphosphatidylcholine (DPPC) and binary mixtures of DPPC:phosphatidylglycerol (PG) in 9:1 and 7:3 ratios were modelled as lung surfactant monolayers and the inhibitory potential of mycolic acid and cord factor on the surface activity of DPPC and DPPC:PG mixtures was evaluated using Langmuir monolayers. The mycobacterial lipids caused common profile changes in all the isotherms: increase in minimum surface tension, compressibility and percentage area change required for change in surface tension from 30 to 10 mN/m. Higher minimum surface tension values were achieved in the presence of mycolic acid (18.2 ± 0.7 mN/m) and cord factor (13.28 ± 1.2 mN/m) as compared to 0 mN/m, achieved by pure DPPC film. Similarly higher values of compressibility (0.375 ± 0.005 m/mN for mycolic acid:DPPC and 0.197 ± 0.003 m/mN for cord factor:DPPC monolayers) were obtained in presence of mycolic acid and cord factor. Thus, mycolic acid and cord factor were said to be inhibitory towards lung surfactant phospholipids. Higher surface tension and compressibility values in presence of tubercular lipids are suggestive of an unstable and fluid surfactant film, which will fail to achieve low surface tensions and can contribute to alveolar collapse in patients suffering from pulmonary tuberculosis. In conclusion a biophysical inhibition of lung surfactant may play a role in the pathogenesis of tuberculosis and may serve as a target for the development of new drug loaded surfactants for this condition.     

Influence of 1-decanol on the surface tension and wetting power of a new anionic surfactant derived from sugar

We studied the adsorption behaviour at the liquid/air and liquid/solid interface of a new anionic surfactant derived from sugar, the sodium decyl galacturonate. The surface tension of aqueous solutions, measured in equilibrium and as a function of time, is particularly affected by the presence of decanol, synthesis residue, which amount ranges between about 0 and 13%. The surface tension lowering is accelerated in presence of decanol, owing to its rapid diffusion to the interface or/and because it affects the mobility and adsorption process of the anionic surfactant molecules. The wetting power of surfactant solutions were also investigated in relation with textile treatment applications. We measured the kinetics of absorption of surfactant solutions in a piece of standard cotton and compared it to the absorption of pure decanol, a completely wetting liquid and to the absorption of an alkylpolyglucoside. The time at which the fabric piece is saturated appears to be related to the adsorption of surface-active molecules on the fibers at the advancing liquid front/fabric contact line. Decanol was found to promote absorption and micellar life-time seem to reflect the differences observed at high concentration. This study shows the importance of controlling the amount of surface-active residues which may alter the kinetics of surfactant adsorption, particularly in industrial processes where equilibrium conditions are not reached.     

Study on the Surface Property of Surfactant Ionic Liquids Solutions

The surfactant TX-100 can be dissolved in ionic liquid bmimPF6 and decrease the surface tension of 1-buty1-3-methylimidazolium hexafluorophosphate (bmimPF6) solutions. Here, we confirmed that in this new system, the pure solvents need rearrangement at the air-wate rinterface at the initial stage. The dynamic surface tension (DST) study shows that at the initial adsorption stage, the adsorption model of surfactant accords with the diffusion-controlled adsorption mechanism, and the dilute ionic liquids solutions is further close to the diffusion-controlled adsorption.     

Different Distributions of Counterions in the Surface Layer of Cationic Surfactant Solutions

We have separately determined the surface tension of pure aqueous solutions of cetyltrimethylammonium chloride and cetyltrimethylammonium bromide and their surface potentials by a Kelvin probe system. With the help of Gibbs equation, the surface excess has been determined through approximating the chemical activity of the surfactant by their dilute bulk concentration. In the following, the surface potential—surface excess isotherms were established. Those potential isotherms evidence that cetyltrimethylammonium chloride solution has a higher value compared to that of cetyltrimethylammonium bromide under equal surface excess. This phenomenon is supposed to be owed to the different distributions of chloride and bromide ions within the adsorption layer of the solutions, which can be attributed to the different properties of those two anions.     

新型磺基甜菜碱/聚丙烯酰胺体系表面及界面性能

采用自制的新型磺基甜菜碱两性表面活性剂与相对分子质量2500万的聚丙烯酰胺进行复配,考察了不同温度和矿化度条件下,聚合物对复配溶液表面、界面性能的影响。 采用滴体积法测定了溶液的表面张力,结果表明,加入聚合物使溶液的临界胶束浓度增大,且复配溶液的表面张力大于单独表面活性剂溶液的表面张力。 当聚合物浓度一定,增大溶液矿化度时,体系表面张力增大。 用旋滴型界面张力仪测定了溶液的界面张力,结果表明,增大聚合物浓度,油水界面张力增大,增大溶液矿化度,油水界面张力有所升高。 聚合物质量浓度为1.5 g/L,表面活性剂质量浓度为0.3 g/L时,可使胜利油田孤岛原油和孤东原油的油水界面张力达到超低数量级（10-3 mN/m）。 用分水时间法测定了溶液的乳化性能,结果表明,聚合物浓度增大,分水时间延长,并考察了75、85和95 ℃条件下体系的乳化性能,温度越高,分水时间越短。     

Dynamic Surface Tension and Adsorption Mechanism of Surfactant Benzyltrimethylammonium Bromide at the Air/Water Interface

The air‐solution equilibrium tension, γ_c and dynamic surface tension, γ_t, of aqueous solutions of a novel ionic surfactant benzyltrimethylammonium bromide (BTAB) were measured by Wilhelmy method and Maximum bubble pressure method (MBPM), respectively. Adsorption equilibrium and mechanism of BTAB at the air‐solution interface were studied. The CMC was determined to be 0.11 mol/L. The results show that at the start, the adsorption process is controlled by a diffusion step. Toward the end, it changes to a mixed kinetic‐diffusion controlled mechanism with the adsorption activation energy of about 11.0 KJ/mol. Effects of temperature, inorganic salts, and alcohols on adsorption kinetics also are discussed.     

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 β^s 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. Received: 20 April 1998 /Accepted in revised form: 27 August 1999     

Dynamic surface activity of phenylalanine glycerol-ether surfactant solutions measured by a differential maximum bubble pressure tensiometer

A refined differential maximum bubble pressure tensiometer was used for measuring the dynamic surface tension at various concentrations of a nonconventional surfactant, a member of a new homologous series of phenylalanine glycerol-ether amphiphiles, with 10 carbon atoms to the hydrophobic alkyl chain (C(10)-PhGE). The effective bubble formation frequency for the examined surfactant concentrations was varied from 2 bubbles per second to 1 bubble per 20 s. The variation of equilibrium surface tension with concentration as well as the critical micelle concentration were determined by a Wilhelmy plate technique. Comparisons between dynamic and equilibrium surface tension values demonstrate that, under the employed surface deformation rates, the equilibrium surface tension is a misleading indicator of surface activity. This is also supported by simple surface rheology considerations. Results based on a diffusion-controlled kinetic analysis provide further evidence on the strong dependence of surface activity on the particular time scale of deformation.