Dynamic surface tension and surface rheology of biological liquids

The paper presents results of dynamic and equilibrium surface tension measurements (using a maximum bubble pressure instrument) of serum and urine samples that were obtained from 80 healthy human of various sexes and ages. These data were compared with surface tension measurements of biological liquids obtained from patients suffering from malignant neoplasm of corpus uteri (n=5) and cervix uteri (n=31). In addition, surface dilatational rheology was determined on 32 samples using a drop shape method. The dilatational rheology data were compared with the dynamic surface tension data. Although some trends were found, no significant correlations exist between surface tension and rheology data and any of the disease states or stages. It is difficult to explain these findings in the framework of known mechanisms. However, our studies demonstrate that dynamic interface tensiometry of human biological liquids provide new insight into the biophysical behavior of these liquids, most likely reflecting compositional changes of them during ageing, the course of cancer and as a consequence of therapeutical interventions.     

How surface tension of surfactant solutions influences the characteristics of sprays produced by hydraulic nozzles used for pesticide application

The sprays produced by hydraulic agricultural nozzles are influenced by the surface tension of the spray liquid, but models of spray formation relate only to pure liquids with constant surface tension. The way surfactant solutions affect spray formation is studied by investigating sprays of pure liquids compared with a range of surfactant solutions. Some surfactants caused changes in the appearance of the liquid sheet produced by the nozzles, which did not occur with pure liquids, and smaller spray drop sizes than pure liquids, suggesting that other surface properties may also be important.     

Rheology and stability of oil-in-water nanoemulsions stabilised by anionic surfactant and gelatin 2) addition of homologous series of sugar-based co-surfactants

The oil-in-water emulsions used in silver-halide photographic coatings are stabilised with anionic surfactants and made in the presence of excess gelatin, which acts as an electrosteric stabilising agent and continuous phase viscosifier. The oil droplet sizes are close to 100 nm but the adsorbed gelatin increases the effective volume of the droplets significantly. These nanoemulsions are manufactured and coated at temperatures in excess of 40 degrees C, where gelatin adopts a random coil structure. At oil concentrations above 15% by volume, the emulsions are viscoelastic liquids with a high low-shear viscosity and strong shear-thinning. The viscosity and shear-thinning can be decreased by reducing the adsorption of gelatin, which can be achieved by addition of nonionic surfactants. This is a rheological study of the effects of adding novel, nonionic sugar-based surfactants on the rheology of photographic nanoemulsions, with additional measurements of static and dynamic surface tension. These surfactants have two sugar (gluconamide) heads and either one or two alkyl tails. Homologous series of each type of sugar surfactant were investigated over a wide range of alkyl tail length. The optimum surfactant choice for commercial applications depends not only on rheological effects but also on ease of synthesis, purification and dissolution, and of course, cost. The dynamic surface tension of the emulsion containing the anionic-nonionic surfactant mixture must also be compatible with the multilayer coating process.     

Investigation Static/Dynamic Surface and Interfacial Tension of Some Synthesized Polymeric Surfactants to Enhance the Egyptian Jet Fuel A1 Atomization

In the present work some exthoxylated polyalkylphenol surfactants have different alkyl chains (nonyl and dodecyl) were synthesized. The static surface tension for these surfactants in water and jet fuel A1 was measured and the critical micelle concentration (CMC) for each surfactant was determined. The data show the general trend of decreasing the CMC against the molecular weight of the synthesized polymeric surfactants. The HLB of these surfactants was also calculated. The dynamic surface tension for the synthesized surfactants was measured at CMC. The dynamic interfacial tension for these surfactants with jet fuel A1 at CMC was also measured using the spinning drop technique. The results showed that the effect of the synthesized surfactants on deceasing the time of droplet maturation was significant remarked. The decrease of this time leads to enhance of jet fuel atomization.     

Determination of the critical surface tension of wetting of minerals treated with surfactants by shear flocculation approach

This paper contributes the shear flocculation method as a new approach to determine the critical surface tension of wetting of minerals treated with surfactants. This newly developed approach is based on the decrease of the shear flocculation of the mineral suspension, with decreasing of the surface tension of the liquids used. The solution surface tension value at which shear flocculation does not occur can be defined as the critical surface tension of wetting (gamma c) of the mineral. By using the shear flocculation method, the critical surface tensions of wetting (gamma c) for calcite and barite minerals, treated with surfactants, were obtained as 30.9 and 35.0 mN/m, respectively. These values are in good agreement with data reported previously on the same minerals obtained by the contact angle measurement and flotation methods. The chemical agents used for the treatment of calcite and barite particles were sodium oleate and sodium dodecyl sulfate, respectively.     

Surface adsorption and micelle formation of surface active ionic liquids in aqueous solution

Aqueous solutions of three kinds of surface active ionic liquids composed of the 1-alkyl-3-methylimidazolium cation have been investigated by means of surface tension and electrical conductivity measurements at room temperature (298 K). The surface tension measurements provided a series of parameters, including critical micelle concentration (cmc), surface tension at the cmc (gammacmc), adsorption efficiency (pC20), and effectiveness of surface tension reduction (Picmc). In addition, with application of the Gibbs adsorption isotherm, maximum surface excess concentration (Gammamax) and minimum surface area/molecule (Amin) at the air-water interface were estimated. The effect of sodium halides, NaCl, NaBr, and NaI, on the surface activity was also investigated. It was found that both the pC20 and the Picmc were rather larger than those reported for traditional ionic surfactants and the cmc values were somewhat lower than those for typical cationic surfactants, alkyltrimethylammonium bromides, and comparable to typical anionic surfactants, sodium alkyl sulfates. These results demonstrate that the surface activity of long-chained imidazolium IL is somewhat superior to that of conventional ionic surfactants.     

Active control of interfacial properties

Recent studies aimed at establishing principles for active control of the physicochemical properties of interfaces have made substantial progress towards demonstrating spatial and temporal control of interfacial properties of both liquids and solids. Light-active and redox-active surfactants have been shown to permit large (>20 mN/m) and reversible changes in the surface tensions of liquids on time-scales of seconds. These changes can be directed to localized regions of liquids with sub-millimeter spatial resolution, thus providing new means to create controlled gradients in surfactant-based properties of liquids (e.g. gradients in surface tension). Progress has also been reported in the electrowetting of liquids on the surfaces of solids, although it is still not possible to use an external electric field to cause an aqueous solution to wet a hydrophobic surface.     

Studies of dynamic surface tension of polyoxyethylene alkylphenols at the air–water interface

This paper presents the study of dynamic surface tension of polyoxyethylene alkylphenol surfactants (Igepals) at the air–solution interface. The experimental investigation of the surface tension dynamics are carried out using a pendant drop method for two of the representative alkylphenols (Igepal-630 and Igepal-720) nonionic surfactants. The general trend of the dynamic surface tension for the two surfactants appears to be similar. However, the absolute surface activities are different. Between the two poloxyethylene alkylphenol surfactants, it was found that Igepal-C0-630 has a higher surface activity and a lower critical micelle concentration (CMC) value. This agreed well with their reported hydrophile–lipophile balance (HLB). The equilibrium adsorption parameters for these surfactant systems have been estimation using two different methods and are in good agreement. The theoretical model developed for the surface tension dynamics based on the Statistical Rate Theory (SRT) in our earlier (J. Colloid Interface Sci., 286, 2005, 14–27) work satisfactorily predicted the experimental results for the present systems.     

Dynamic Behavior of Surfactants in Solution

Adsorption of various surfactants at the gas liquid interface is studied with equilibrium and dynamic surface tension measurements. The Wilhelmey plate method and maximum bubble pressure method are used for this study. Dynamic surface tension of solutions of different surfactants, sodium lauryl sulfate (SLS), polyoxyethylene glycol 4‐tert‐octyl phenyl ether (Triton X 100), poly‐oxyethylene(20) cetyl ether (Brij 58), and tetraethylene glycol mono‐n‐dodecyl ether (Brij 30), is measured at different concentrations. Adsorption of different surfactants is compared on the basis of equilibrium and dynamic behavior. Effectiveness and efficiency of different surfactants is found from equilibrium surface tension measurement. A new parameter is defined to quantify the dynamic behavior of adsorption, which gives the concentration of surfactant needed to reduce surface tension to half of its maximum reduction within a defined time available for adsorption. The dynamics of surfactant solution is quantified by using this parameter.     

Interfacial tensiometry method for the analysis of model systems in comparison with blood as the most important biological liquid

Interfacial tensiometry of various liquids is an informative colloid-chemical method for the analysis of various liquids in many areas of natural sciences and medical practice. This method of dynamic surface tension (DST) measurements is proposed for the study of animal blood plasma or serum and mixtures of proteins, lipids, and salts as model systems. It is found that the saline affects lecithin aqueous dispersions significantly more weakly than those of the proteins. The DST values and biochemical parameters of the bovine blood serum of the same sample are obtained. Correlations between DST values and biochemical parameters of blood serum are found. They are both of fundamental and practical importance in laboratory diagnostics.     

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.     

Headgroup and hydrocarbon tail effects on the surface tension of sugar-based surfactant solutions

Measurements of surface tension isotherms were conducted for water solutions of pure and mixed n-decyl-beta-d-glucopyranoside (C(10)-Glu) and n-decyl-beta-d-maltopyranoside (C(10)-Mal) surfactants. By applying the Gibbs surface tension equation, the surface densities of Glu and Mal were derived for different compositions and concentrations. The surface fractions were compared with theoretically calculated values where the headgroups were modeled as hard disks. Satisfactory agreement was found for hard-disk sizes of 22.9 and 11.3 A(2) in the case of a 1:1 mixture. The results of the hard-disk calculations were employed to estimate the configurational free energy of the n-decyl-hydrocarbon chain. The results obtained agree well with previous calculations for the n-dodecyl chain. Comparison with n-dodecyl beta-d-maltopyranoside (C(12)-Mal) indicated a further contribution, with the longer hydrocarbon chain giving rise to a higher surface tension in good agreement with data for hydrocarbon liquids. Furthermore, the interpenetration of the headgroup into the hydrocarbon film was studied by means of comparing surface-tension data for n-decyl- and n-dodecyl-ethylene-oxide-based surfactants and n-decyl- and n-dodecyl-beta-d-thiomaltopyranosides (C(10)-S-Mal and C(12)-S-Mal, respectively) and -maltopyranosides. It was found that lengthening the tetra(etylene oxide) chain by one segment affects the surface tension only marginally, indicating little interpenetration of the additional ethylene-oxide group into the hydrocarbon film. For the thiomaltosides, however, the corresponding effect was found to be remarkably high.     

Silicon-modified carbohydrate surfactants VI: Synthesis of carbosilane,silane, polysilane and non-permethylated siloxane derivatives; the wetting behaviour of epoxy-modified precursor liquids on non-polar surfaces

The synthesis of carbohydrate surfactants bearing carbosilane, silane, polysilane and non-permethylated siloxane moieties is described. These surfactants consist of three structural elements: (1) a silicon-containing moiety, (2) a spacer and (3) a carbohydrate unit. Additionally two different types of mixed structures have been synthesized: (a) single-chained carbosilane–siloxane surfactants and (b) double-chained combinations of carbo- silanes, silanes and siloxanes. The wetting behaviour of the key intermediates, the allyl glycidyl derivatives, has been investigated by static surface tension (γ_lv, σ) and wetting tension (γ_sv−γ_sl, α) measurements on a non-polar perfluorinated surface (FEP® plate). The contact angles obtained for these pure liquids are not a linear function of the surface tension but depend on the polarity of the substructures. © 1998 John Wiley & Sons, Ltd.     

Self-aggregation of nonionic surfactants in imidazolium-based ionic liquids with trifluoromethanesulfonate anion

Self-aggregation of polyoxyethylene (POE)-type nonionic surfactants in ionic liquids, 1-butyl- and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (bmimCF₃SO₃ and emimCF₃SO₃), was investigated by means of ¹H-NMR chemical shift, dynamic light-scattering (DLS), and surface tension measurements. The surfactants showed no definite aggregate formation in bmimCF₃SO₃. This shows a remarkable contrast to the previous observation in bmimBF₄ and bmimPF₆, and demonstrates an importance of anion species to determine the property of ionic liquids as a solvent to support the self-assembly of amphiphilic compounds. On the other hand, the surfactants formed micelles in emimCF₃SO₃, which shows an importance of alkyl chain attached to imidazolium ring to determine the solvophobic interaction between surfactant hydrocarbon chains in imidazolium-based ionic liquids. The low solvophobicity of the surfactants to the ionic liquid composed of imidazolium cation with long alkyl chain is attributed to an affinity of the surfactant hydrocarbon chain to the imidazolium alkyl chain. The values of micellization parameters and surface adsorption parameters obtained for the surfactant solutions in emimCF₃SO₃ are reported.     

Microfluidic approach for rapid interfacial tension measurement

A novel microfluidic approach to measure interfacial tension of immiscible fluids rapidly is reported. This method rests upon quantitative force balance analysis of drop formation dynamics in a coaxial microfluidic device. The values of interfacial tension for several two liquids without/with surfactants are measured. These measurements compare well with those measured by the commercial interfacial tensiometry. The viscosity of water phase fluid can also be accurately measured in the same microfluidic device. Several model systems with interfacial tension from 1.0 to 10.0 mN/m and water phase viscosity from 1.0 to 10.0 mPa.s are tested in this work.     

Synthesis of newly cationic surfactant based on dimethylaminopropyl amine and their silver nanoparticles: Characterization; surface activity and biological activity

The chemical structure of newly synthesized cationic surfactants based on Schiff base was confirmed using Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and mass spectroscopy. The synthesized surfactants were used in the synthesis of silver nanoparticles by a simple one-step method. The silver nanoparticle (AgNPs) formation was confirmed using transmission electron microscopy (TEM), electron diffraction (SAED), dynamic light scattering (DLS), and energy dispersive X-ray spectroscopy (EDX). The structure of the surfactant played an important role in the synthesis process. Increasing the hydrophobic chain length, the stability, and the amount of surfactant increased the quantity of AgNPs formed. The surface activity of the synthesized cationic surfactants was determined using surface tension measurements at three different temperatures. The synthesized surfactants showed a high tendency toward adsorption and micellization. Increasing the hydrophobic chain length of the synthesized surfactant increased its adsorption. Screening the synthesized cationic surfactants and their nano-form against bacteria and fungi showed that they are highly effective. The silver nanoparticles enhanced the biological activity of the synthesized cationic surfactants.     

CMC系列高分子表面活性剂与原油超低界面张力形成机理的研究

采用动态激光光散射及环境扫描电镜研究了羧甲基纤维素系列高分子表面活性剂与大庆原油形成超低界面张力的机理.结果表明,CMC系列高分子表面活性剂具有与低分子量表面活性剂相比拟的表/界面活性,其水溶液的表面张力可达2835mN/m,界面张力达到10^-110mN/m.碱的加入可显著降低高分子表面活性剂与原油的界面张力,在适当条件下界面张力达到超低值(10^-3mN/m),可望作为三次采油的驱油剂.等效烷烃模型研究表明,用碱与原油酸性组分的作用来解释碱能使界面张力下降至超低值的传统观点是不完善的,加入碱能使高分子表面活性剂胶束解缔,胶束数量增多,胶束粒径减小,单分子自由链增加,有利于高分子表面活性剂向界面迁移和排布,这是高分子表面活性剂和碱复配体系与原油界面张力下降至超低值的主要原因.     

Effect of Neck Formation on the Measurement of Dynamic Interfacial Tension in a Drop Volume Tensiometer

Dynamic interfacial tension values obtained by drop volume tensiometry will be affected under certain experimental conditions by the formation of a neck between the drop and the capillary tip. This phenomenon must be accounted for to obtain accurate values of interfacial tension. In this work, neck formation for a water–mineral oil system is studied under conditions where hydrodynamic effects can be neglected. A model originally developed for the determination of the surface tension of a suspended drop is modified for application to dynamic interfacial tensions of surfactant-containing liquids. The model relates apparent values of interfacial tension calculated from drops possessing necks to actual values. Experiments with Span 80 (sorbitan monooleate) and sodium dodecyl sulfate (SDS) surfactants in a mineral oil–water system are used to test the validity of the developed model. For the small tip diameter used, good agreement is obtained for Span 80 up to the critical micelle concentration, and for low concentrations of SDS, when the surfactant adsorption is diffusion-limited. In both cases, the neck diameter of the growing drop can be considered constant over the range of dynamic interfacial tensions tested.     

Surface tension and refractive index of pure and water-saturated tetradecyltrihexylphosphonium-based ionic liquids

Experimental data on the surface tension and refractive index of tetradecyltrihexylphosphonium-based ionic liquids with bromide, chloride, decanoate, methanesulfonate, dicyanimide, bis(2,4,4-trimethylpentyl)phosphinate and bis(trifluoromethylsulfonyl)imide anions are reported. The data were obtained for pure and water saturated samples at temperatures from 283 K to 353 K and at atmospheric pressure. The refractive index of the investigated ionic liquids decreases with increasing the water content in the sample. On the other hand, no clearly dependence of the surface tension with the water content up to a weight fraction of 16% was found. The prediction of the refractive index for the studied ionic liquids was also accomplished by a group contribution method and new values for the cation and diverse anions were estimated and proposed. The studied ionic liquids show lower surface tension in comparison with imidazolium-, pyridinium- or pyrrolidinium-based ionic liquids with a similar anion; also they show higher surface entropy than cyclic nitrogen-based fluids which indicates a lower surface organization. The anion dependence of the surface tension and surface entropy for the investigated ionic liquids is weaker than that for short-chain imidazolium-based ionic liquids. Their critical temperatures evaluated from Eötvos and Guggenheim equations are also lower than those of N-heterocyclic ionic fluids.     

Hofmeister效应对生物和化学体系的影响

Hofmeister效应涉及到的问题范围十分广泛,对很多化学、生物体系都有影响。总的说来,Hofmeister效应会影响到溶液的冰点、沸点、黏度、偏摩尔体积、饱和蒸汽压、传导率、pH、表面张力。文章主要介绍了Hofmeister效应的主要影响因素,以及相关理论的建立与完善,并对不同体系中Hofmeister效应的影响进行了描述。