Mixtures Of Hydrocarbon Surfactants Research Articles

Stability and thinning behaviour of aqueous foam films containing fluorocarbon and hydrocarbon surfactant mixtures

The stability and thinning behaviour of the liquid foam film containing fluorocarbon and hydrocarbon surfactant mixtures were investigated quantitatively by using the optical interferometry technique. Multiscale characterization methods were employed to study the relationships between foam stability, film thinning behaviour, and bulk and interfacial properties. The results show that the liquid film from the SDS solution is unstable with rapid marginal regeneration. Adding fluorocarbon surfactant FC1157 can significantly enhance film stability and slow down liquid drainage rates of the liquid film. For the SDS film with mobile surfaces, the film thinning process follows a power-law behaviour and the thinning exponent becomes less negative by increasing FC1157 concentrations. At very high FC1157 concentrations, the film surface becomes relatively immobile and the thicknesses profile is close to the theoretical prediction of a rigid film. It should be emphasized that the bulk aggregation and surface adsorption behaviours of surfactants affect the thinning rate and stability of the liquid film. Large aggregates assembled from FC1157 molecules produce a viscous solution that offers high resistance to liquid motion. Due to low compression velocities at the film border, the film containing SDS/FC1157 mixtures with relatively immobile surfaces has larger marginal regeneration wavelengths than that of the mobile film stabilized by SDS alone. In addition, foam stability results indicate that there is a qualitative relationship between the macroscale foam and microscale single film in terms of their lifetime.

Work of adhesion and activity of aqueous solutions of ternary mixtures of hydrocarbon and fluorocarbon nonionic surfactants at the water–air and polymer–water interfaces

The values of the surface tension and contact angle on the polytetrafluoroethylene surface (PTFE) of aqueous solutions of the ternary mixtures of hydrocarbon surfactants, TX100 and TX165, and fluorocarbon FSN100 at different mole fractions of surfactants in the bulk phase were applied for the studies of the correlation between the adsorption of surfactants at the solution–air and polymer–solution interfaces, the work of adhesion determined from the Young–Dupree equation, the parameter of the intermolecular interactions and the spreading coefficient of aqueous solutions of the studied mixtures on the PTFE surface. For this purpose the values of the total mole fraction and activity of surfactants at the polymer–solution interface obtained from the Sprow and Prausnitz equation were compared to those at the solution–air one. Also on the basis of the mole fraction of the particular surfactants at the PTFE–solution and water–air interface and on the assumption of the additivity of the adhesion work, the work of adhesion of the fluorocarbon tail to the PTFE surface as well as the Lifshitz–van der Waals component of the PTFE surface tension were calculated.

Phase Behavior, Rheological Property, and Transmutation of Vesicles in Fluorocarbon and Hydrocarbon Surfactant Mixtures

We present a detailed study of a salt-free cationic/anionic (catanionic) surfactant system where a strongly alkaline cationic surfactant (tetradecyltrimethylammonium hydroxide, TTAOH) was mixed with a single-chain fluorocarbon acid (nonadecafluorodecanoic acid, NFDA) and a hyperbranched hydrocarbon acid [di-(2-ethylhexyl)phosphoric acid, DEHPA] in water. Typically the concentration of TTAOH is fixed while the total concentration and mixing molar ratio of NFDA and DEHPA is varied. In the absence of DEHPA and at a TTAOH concentration of 80 mmol·L(-1), an isotropic L(1) phase, an L(1)/L(α) two-phase region, and a single L(α) phase were observed successively with increasing mixing molar ratio of NFDA to TTAOH (n(NFDA)/n(TTAOH)). In the NFDA-rich region (n(NFDA)/n(TTAOH) > 1), a small amount of excess NFDA can be solubilized into the L(α) phase while a large excess of NFDA eventually leads to phase separation. When NFDA is replaced gradually by DEHPA, the mixed system of TTAOH/NFDA/DEHPA/H(2)O follows the same phase sequence as that of the TTAOH/NFDA/H(2)O system and the phase boundaries remain almost unchanged. However, the viscoelasticity of the samples in the single L(α) phase region becomes higher at the same total surfactant concentration as characterized by rheological measurements. Cryo-transmission electron microscopic (cryo-TEM) observations revealed a microstructural evolution from unilamellar vesicles to multilamellar ones and finally to gaint onions. The size of the vesicle and number of lamella can be controlled by adjusting the molar ratio of NFDA to DEHPA. The dynamic properties of the vesicular solutions have also been investigated. It is found that the yield stress and the storage modulus are time-dependent after a static mixing process between the two different types of vesicle solutions, indicating the occurrence of a dynamic fusion between the two types of vesicles. The microenvironmental changes induced by aggregate transitions were probed by (19)F NMR as well as (31)P NMR measurements. Upon replacement of NFDA by DEHPA, the signal from the (19)F atoms adjacent to the hydrophilic headgroup disappears and that from the (19)F atoms on the main chain becomes sharper. This could be interpreted as an increase of microfluidity in the mixed vesicle bilayers at higher content of DEHPA, whose alkyl chains are expected to have a lower chain melting point. Our results provide basic knowledge on vesicle formation and their structural evolution in salt-free catanionic surfactant systems containing mixed ion pairs, which may contribute to a deeper understanding of the rules governing the formation and properties of surfactant self-assembly.

Hydrothermal Synthesis of Ordered Mesoporous Materials with High Stability at High Temperatures

The hydrothermal synthesis of ordered mesoporous materials with high stability at high temperatures is currently a hot topic in the materials field.This review covers recent developments in the synthesis of ordered mesoporous silicas, titanosilicates and polymer materials with high hydrothermal stability at high temperatures.The uses of fluorocarbon and hydrocarbon surfactant mixtures and solo hydrocarbon surfactants are also discussed.

Aggregation Behavior of Fluorocarbon and Hydrocarbon Cationic Surfactant Mixtures: A Study of 1H NMR and 19F NMR

The aggregation behavior and the interaction of four mixed systems for a cationic fluorocarbon surfactant, diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMACl), mixing with cationic hydrocarbon surfactants, alkyltrimethylammonium chloride, CnTACl (n=12, 14, 16, and 18; where n=12 is DTACl, n=14 is TTACl, n=16 is CTACl, and n=18 is OTACl), were studied by 1H and 19F NMR in more detail. The results of 19F NMR measurements strongly indicate that in the three mixed systems of DEFUMACl/DTACl, DEFUMACl/TTACl, and DEFUMACl/CTACl at different molar fractions of fluorocarbon surfactant (alphaF=(cDEFUMACl/cDEFUMACl+cCnTACl)), with an increase of the total concentration of fluorocarbon and hydrocarbon surfactants (cT=cF+cH), the mixed micelles at the first break point and the individual DEFUMACl micelles at the second break point form. However, three different types of micelles were determined in DEFUMACl/OTACl mixtures by 19F NMR measurements, OTACl-rich and DEFUMACl-rich mixed micelles and individual DEFUMACl micelles, respectively. The chemical shifts of proton Deltadelta (1H) for -CH3 in the mixed systems of DEFUMACl/CnTACl (n=12, 14, 16, and 18) have different variation trends from the 19F NMR measurements. For the two systems of DEFUACl/DTACl and DEFUMACl/TTACl, the mixed micelles form at the first break point. At the second break point, for lower alpha F values the DTACl-rich and TTACl-rich mixed micelles form with a strong downfield shift and for higher alpha F values DEFUMACl-rich mixed micelles form with a strong upfield. For the other two systems of DEFUMACl/CTACl and DEFUMAC/OTACl, the chemical shifts of proton Deltadelta (1H) of -CH3 increase with an increase of the total concentration of DEFUMACl/CTACl or OTACl, and mixed CH- and CF-surfactant micelles form. At higher total concentration, the greater effect of fluorinated chains of DEFUMACl on CH-chains was obvious, resulting in the strong upfield chemical shifts. In cationic fluorocarbon and hydrocarbon surfactant mixtures, the different kinds of micelles observed by 19F and 1H NMR measurements could be caused by the increase in alkyl chain length of hydrocarbon surfactants with different critical micelle concentrations. Combining two theoretical models for mixing, for the four different chain-length hydrocarbon surfactants studied, one can conclude that the two components of mixtures interact with each other and form mixed micelles in two completely different ways according to their molecular properties and cmc values in a certain range of total concentrations. One is close to an ideal mixing case with the formation of one type of mixed micelles, such as the DEFUMACl/DTACl and DEFUMACl/TTACl systems. The other is a demixing case with the formation of two types of micelles, i.e., fluorocarbon-rich and hydrocarbon-rich mixed micelles, such as DEFUMACl/CTACl and DEFUMACl/OTACl systems. However, as the total concentrations of the mixed systems are high enough, the four systems tend to demix and to form individual micelles of corresponding components due to the initial respective interaction between fluorocarbon and hydrocarbon chains. That is to say, at high total concentration, the individual DEFUMACl micelles in all four systems could form. These results may be primarily directed toward acquiring an understanding of the mechanism of CF-CH mixtures in aqueous solution and secondarily directed toward providing more detailed information on nonideal mixing.

Dynamics of Spontaneous Vesicle Formation in Fluorocarbon and Hydrocarbon Surfactant Mixtures

The spontaneous self-assembly of unilamellar vesicles was investigated by means of time-resolved synchrotron small-angle X-ray scattering. The self-assembly process was initiated by rapid mixing of anionic surfactant micelles with either zwitterionic or cationic surfactant micelles in equimolar ratio using a stopped-flow device. For the zwitteranionic systems, transient disklike mixed micelles are observed as structural intermediates prior to the onset of vesiculation. These disklike micelles display an exponential growth law, and above a critical size they close to form unilamellar vesicles. In the catanionic system, the earliest observable structures within the mixing time of 4 ms are unilamellar vesicles. Nevertheless, in both systems a narrow distribution of the vesicle size was observed at the initial stages of their formation. The subsequent evolution of the vesicle size distribution depends on the subtle differences in the bilayer composition and properties.

High-temperature synthesis of stable ordered mesoporous silica materials by using fluorocarbon-hydrocarbon surfactant mixtures.

Highly ordered hexagonal mesoporous silica materials (JLU-20) with uniform pore sizes have been successfully synthesized at high temperature (150-220 degrees C) by using fluorocarbon-hydrocarbon surfactant mixtures. The fluorocarbon-hydrocarbon surfactant mixtures combine the advantages of both stable fluorocarbon surfactants and ordered hydrocarbon surfactants, giving ordered and stable mixed micelles at high temperature (150-220 degrees C). Mesoporous JLU-20 shows extraordinary stability towards hydrothermal treatment (100 % steam at 800 degrees C for 2 h or boiling water for 80 h), thermal treatment (calcination at 1000 degrees C for 4 h), and toward mechanical treatment (compressed at 740 MPa). Transmission electron microscopy images of JLU-20 show well-ordered hexagonal arrays of mesopores with one-dimensional (1D) channels and further confirm that JLU-20 has a two-dimensional (2D) hexagonal (P6 mm) mesostructure. 29Si HR MAS NMR spectra of as-synthesized JLU-20 shows that JLU-20 is primarily made up of fully condensed Q4 silica units (delta=-112 ppm) with a small contribution from incompletely cross-linked Q3 (delta=-102 ppm) as deduced from the very high Q4/Q3 ratio of 6.5, indicating that the mesoporous walls of JLU-20 are fully condensed. Such unique structural features should be directly attributed to the high-temperature synthesis, which is responsible for the observed high thermal, hydrothermal, and mechanical stability of the mesoporous silica materials with well-ordered hexagonal symmetry. Furthermore, the concept of "high-temperature synthesis" is successfully extended to the preparation of three-dimensional (3D) cubic mesoporous silica materials by the assistance of a fluorocarbon surfactant as a co-template. The obtained material, designated JLU-21, has a well-ordered cubic Im3m mesostructure with fully condensed pore walls and shows unusually high hydrothermal stability, as compared with conventional cubic mesoporous silica materials such as SBA-16.

External Reflection FTIR Spectroscopy of the Cationic Surfactant Hexadecyltrimethylammonium Bromide (CTAB) on an Overflowing Cylinder

External reflection Fourier transform infrared spectroscopy (ER-FTIRS) has been used to study the adsorption of the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) at the air-water interface under nonequilibrium conditions. An overflowing cylinder (OFC) was used to generate a continually expanding liquid surface with a surface age of 0.1-1 s. ER-FTIR spectra were acquired by a single bounce of p- or s-polarized radiation from the flowing surface of the OFC. The C-H stretching region of CTAB spectra was analyzed both by subtraction of a reference spectrum of pure water and by a chemometric technique known as target factor analysis (TFA). The TFA method is shown to give lower scatter in the weight of the component assignable to the adsorbed CTAB monolayer and to permit analysis of spectra at lower bulk surfactant concentrations. The surface sensitivity of ER-FTIRS is demonstrated both experimentally and by theoretical modeling. Modeling shows that surfactant adsorbed at the surface and dissolved in the bulk solution can be distinguished by reflection spectroscopy but also highlights potential errors that can arise from the neglect of the bulk surfactant contribution to the ER-FTIR spectra. Polarized spectra are consistent with an isotropic distribution of transition dipole moments of the hydrocarbon chains in CTAB. Component weights of the CTAB monolayer determined by TFA are compared with an independent determination of values of the dynamic surface excess, Gammadyn, by neutron reflection and ellipsometry. The relationship between the component weights and Gammadyn shows a small but significant deviation from linearity. Possible explanations for this deviation are discussed. The feasibility of using TFA to deconvolute ER-FTIR spectra of mixtures of hydrocarbon surfactants is demonstrated.

Appearance of pure fluorocarbon micelles surveyed by fluorescence quenching of amphiphilic quinoline derivatives in fluorocarbon and hydrocarbon surfactant mixtures.

A halide-sensitive fluorescence probe was utilized to evaluate the miscibility of fluorocarbon and hydrocarbon surfactants in aqueous micellar systems. The fluorescence of 6-methoxy-N-1,1,2,2-tetrahydroheptadecafluorodecylquinolinium chloride, FC10MQ, was quenched by halide ions dissociated from the surfactant. The fluorescence in micellar solutions showed an initially rapid decay. This suggests that halide ions effectively quench FC10MQ fluorescence at the micellar surface. The subsequent slow decay corresponds to the quenching of FC10MQ fluorescence in the aqueous bulk phase by the free counterions. The Stern-Volmer plots for fluorescence quenching gave a distinct break at the critical micelle concentration of the cationic surfactants. The abrupt increase in fluorescence quenching is attributed to the solubilization of the probe in the micelles. The fluorescence quenching behavior provides direct information about the immiscibility of fluorocarbon and hydrocarbon species in micelles, and the results indicate that almost pure fluorocarbon micelles appear in surfactants mixtures.

High-temperature generalized synthesis of stable ordered mesoporous silica-based materials by using fluorocarbon-hydrocarbon surfactant mixtures.

Highly ordered mesoporous silica materials are hydrothermally synthesized at high temperature by using fluorocarbon–hydrocarbon surfactant mixtures as templates. Because of the high temperature of the synthesis, the obtained materials show complete silica condensation, which give rise to ultra-stabile structures. JLU-20 for example (see TEM image of calcined JLU-20) has a fully condensed mesopore wall with a very high Q4/Q3 ratio of 6.5.

High‐Temperature Generalized Synthesis of Stable Ordered Mesoporous Silica‐Based Materials by Using Fluorocarbon–Hydrocarbon Surfactant Mixtures

Hoch geordnete, mesoporöse SiO2-Strukturen wurden durch Hydrothermalsynthese mit Fluoralkan/Alkan-Tensid-Mischungen als Templaten erhalten. Aufgrund der hohen Reaktionstemperatur ist die Silicatkondensation vollständig, und die Produkte sind besonders stabil. JLU-20 z. B. (siehe TEM-Bild einer calcinierten Probe) hat eine vollständig kondensierte Porenwand mit einem hohen Q4/Q3-Verhältnis von 6.5.

Micellization of cationic fluorocarbon and hydrocarbon surfactant mixture: Diethanolheptadecafluoro-2-undecanolmethylammonium chloride and dodecyltrimethylammonium chloride mixed system

To reveal the interaction between cationic fluorocarbon and cationic hydrocarbon surfactants, the mixed critical micelle concentration (CMC) of diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMAC) and dodecyltrimethylammonium chloride (DTAC) in aqueous solution was determined using electrical conductivity measurements. An interaction parameter, β, of 1 was obtained by applying a regular solution theory (RST) to the mixed CMC. Further, partition coefficients of alcohols and pyrene-3-carboxaldehyde between the micelles and the aqueous phase were measured. All these data were interpretable using RST with β = 1, indicating a rather small repulsive interaction between DEFUMAC and DTAC compared with anionic fluorocarbon and hydrocarbon surfactant mixtures. This is due to the large different CMC values of the two surfactants.

Micellization of Fluorocarbon and Hydrocarbon Surfactant Mixtures

Micellization of fluorocarbon and hydrocarbon surfactant mixtures in aqueous solution is reviewed. Simple fluorocarbon surfactant micelles can be characterized by growth from sphere to rod-and disk-like form, which is explained by packing constraint. Non-ideality of the mixed systems with head groups of same charge is summarized using interaction parameter calculated by Shinoda's equation. Examples of mixing of separate micelles in the concentrated solutions are given. The mixed systems with different head groups are described from the stand point of micellar growth and vesicle forming.

Mixed Micelle and Mixed Adsorbed Film Formations of Anionic Fluorocarbon-Nonionic Hydrocarbon Surfactant Mixtures Sodium Perfluorooctanoate with MEGA-8, 9 and 10

The formation of mixed micelles and mixed adsorbed films was investigated as a function of the mole fraction of each surfactant mixture for different combinations of an anionic fluorocarbon surfactant, sodium perfluorooctanoate (SPFO) with three nonionic hydrocarbon surfactants, MEGA-8, 9 and 10 (alkyl-N-methylglucamines) in water at 30°C. The results were obtained primarily from surface tension and ESR measurements. The critical micelle concentration (cmc) data for the MEGA-9-MEGA-10 mixed system included those determined from light scattering measurements. Based on the results obtained, the following conclusions were drawn. Mixing of MEGA- n's with SPFO synergetically enhances surface activity, and the cmc vs. composition curves for these show a negative deviation from ideal mixing. Thus possibly, interactions between head groups influence more for the curve than the mutual phobicity between hydrocarbon-fluorocarbon chains. The composition of micelles resembles that of adsorbed films for MEGA- n's-SPFO. ESR data indicate that SPFO and MEGA-n may mix well with each other.

Probe methods for the second cmc of fluorocarbon and hydrocarbon surfactant mixtures

Determination par spectrometrie RMN et par fluorescence, de la concentration critique micellaire des melanges perfluorooctanesulfonate de lithium/dodecylsulfate de lithium et perfluorooctanesulfonate de lithium/tetradecylsulfate de lithium

Fluorine nuclear magnetic resonance of fluorocarbon and hydrocarbon surfactant mixtures

Etudes des interactions dans les micelles mixtes fondees sur le deplacement chimique de 19 F du groupe CF 3 dans les systemes mixtes de tensioactifs fluorocarbure et hydrocarbure. Cas des perfluorooctanesulfonate de Li ou de Na et des decyl- ou -laurylsulfate de sodium