Cationic Fluorocarbon Surfactant Research Articles

Phase Behavior and Phase Structure of a Cationic Fluorosurfactant in Water

The phase behavior of the cationic fluorocarbon surfactant 1,1,2,2-tetrahydroperfluorodecylpyridinium chloride in water has been studied using small-angle X-ray and 2H NMR spectroscopy as the main techniques. The following phase sequence was found: micellar (L1), hexagonal (HI), centered rectangular (R; spacegroup c2mm) and centered trigonal (T, spacegroup R3m) with increasing surfactant concentration. At higher concentrations evidence for random mesh phase and a lamellar phase was found, at high temperatures a bicontinuous cubic phase was found. Compared to a cationic hydrocarbon surfactant of similar hydrophobicity, the occurrence of the intermediate phases is more extensive in the phase diagram, and the fluorocarbon surfactant prefers to form intermediate phases instead of a cubic phase. The surface curvature of the aggregates changes from highly curved cylindrical structures of the hexagonal phase to the planar bilayer structure of the lamellar phase over a sequence of geometries that allow the aver...

Aggregation Behavior of Cationic Fluorosurfactants in Water and Salt Solutions. A CryoTEM Survey

The aggregation behavior of the cationic fluorocarbon surfactants 1,1,2,2-tetrahydroperfluoroalkylpyridinium chloride and 2-hydroxy-1,1,2,3,3-pentahydroperfluoroalkyldiethylammonium chloride in aqueous solution have been studied using cryo-transmission electron microscopy as the main technique. The effects on aggregate structure of factors such as surfactant and salt concentration, counterion type, and alkyl chain length were investigated. Similar to hydrocarbon surfactants the fluorocarbon surfactants self-assemble into various aggregates such as micelles, threadlike micelles, vesicles, and other lamellar aggregates. A distinctive property of the fluorocarbon surfactants is their tendency to form structures with little curvature, such as cylindrical micelles and bilayer structures. Even a very small reduction of the repulsion between the headgroups is sufficient to accomplish a sphere to rod transition, so that a solution of globular micelles in water is turned into a highly viscous, sometimes viscoelastic solution on the addition of low concentrations of a simple salt. The differences between the fluorocarbon and hydrocarbon surfactants are discussed.

Micellar Pseudophase Separation Regions of 1H,1H,2H,2H-Perfluoroalkylpyridinium Chloride and Hydrocarbon Surfactants by Group Contribution Method

New cationic fluorocarbon surfactants 1H,1H,2H,2H-perfluorooctylpyridinium chloride (HFOPC) and 1H,1H,2H,2H-perfluorodecylpyridinium chloride (HFDePC), are synthesized and their cmc's have been determined by the conductivity method. HFOPC -DPC (dodecylpyridinium chloride) and HFDePC-CTAC (cetyltrimethylammonium chloride) mixed systems were investigated from the viewpoint of micellar miscibility. The mutual solubilities of fluorocarbon and hydrocarbon in the micellar phase are predicted by the group contribution method. One can estimate the micellar pseudophase separation regions by using the molecular structure data and the group interaction parameters and predict the alkyl chain length dependence of immiscibility without additional parameters.

Interaction between cationic fluorocarbon surfactant and polyoxyethylated surfactants having a sulfate group

Interaction between a cationic fluorocarbon surfactant, bis(2-hydroxyethyl)(2-hydroxy-3-perfluorooctylpropyl)-methylammonium chloride (DEFUMAC) and sodium dodecyl poly(oxyethylene)sulfate (SDE n S, n = 3, 5, 8) in dilute aqueous solutions has been investigated by means of surface tension, fluorescence probing, solubilization, and static and dynamic light scattering measurements. The same systems in concentrated aqueous solutions have been characterized from the phase diagram. In the concentrated solution no crystals are formed at any molar fraction in the DEFUMAC-SDE 8S system, whereas precipitation of crystals is observed over wide regions in the DEFUMAC-SDE 3S or SDE 5S systems. On the other hand, in the dilute solution, the mixed critical micelle concentration (CMC), the surface tension at the CMC, an interaction parameter β (from regular solution theory), the apparent aggregation number and the diffusion coefficient of the mixed micelles all depend on the oxyethylene chain length of SDE n S. These characteristics change markedly with decreasing value of n. This is predominantly due to the strong electrostatic attractive interaction between the surfactants in spite of the mutual phobicity of hydrocarbon and fluorocarbon chains.

Micellization of fluorocarbon surfactants in mixtures of water and polar solvents

Micellization of anionic and cationic fluorocarbon surfactants in mixtures of ethylene glycol H 2O and ethanol H 2O has been investigated by measuring surface tension and absorption spectra of a dye. The critical micelle concentration (CMC) values of both surfactants determined from the surface tension measurement decrease and then increase with an increase of ethylene glycol or ethanol concentration in the mixtures. In higher concentrations of ethanol, in which the CMC can not be determined from the surface tension measurement, the dye method is useful to estimate the CMC of both surfactants.

Mixed micelles involving a cationic fluorocarbon surfactant

Micellization of a cationic fluorocarbon surfactant with surfactants having various head groups in aqueous solution is discussed. The cationic fluorocarbon surfactant micelles can be characterized by growth from sphere to rod-like form, which is explained by counterion binding and packing ratio. Non-ideality of the mixed surfactant systems using interaction parameters obtained from a regular solution theory is greater for the cationic—cationic than for the cationic—non-ionic systems. The cationic—anionic systems show a larger negative interaction parameter and in particular, in the cationic fluorocarbon—anionic hydrocarbon mixed system, vesicles are formed.

Vesicle Formation in Aqueous Mixtures of Anionic Hydrocarbon and Cationic Fluorocarbon Surfactants

The formation of vesicles in aqueous mixtures of a single-chain anionic hydrocarbon surfactant, lithium dodecyl sulfate (LiDS), and a cationic fluorocarbon surfactant, bis (2-hydroxy ethyl) (2-hydroxy-3-perfluorooctyl propyl) methylammonium chloride (DEFUMAC), was confirmed. The vesicles were formed in all lamellar phase regions at a total surfactant concentration; C t of 10 mmol.dm −3 . Vesicles size showed a wide range of distribution, the average becoming larger as the mixed ratio approached an equimolar ratio.

Adsorption of Poly (styrenesulfonate) and Cationic Fluorocarbon Surfactant from their Mixed Solutions on Particles

Adsorption of Poly (styrenesulfonate) and Cationic Fluorocarbon Surfactant from their Mixed Solutions on Particles

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.

Micellar properties and growth of cationic fluorocarbon surfactant; diethanolheptadecafluoro-2-undecanolmethylammonium chloride

The micellar properties of a cationic fluorocarbon surfactant, diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMAC), are studied by surface tension, fluorescence of pyrene-3-carboxaldehyde (PCA), and electric conductivity measurements. These measurements indicate that DEFUMAC solution provides a low surface tension and that its micelles present higher polar conditions under PCA than do cationic hydrocarbon surtactant micelles. Moreover, the micellar elongation induced by increasing concentrations of salt and surfactant concentration is observed by use of dynamic light scattering, transient electric birefringence, and viscosity measurements. The elongation by addition of salt can be explained by a multiple equilibrium description, while the elongation by increasing surfactant concentration is rapid above a particular concentration, viz. second CMC. Consequently, DEFUMAC micelle elongates more rapidly than do corresponding cationic hydrocarbon surfactants with chloride counterion.

Sessile drops of surfactant solutions on nonhorizontal solid surfaces

The effects of surface active agents on contact angle hysteresis is examined by photographing sessile drops at the point of incipient motion on an inclined solid. For solutions of anionic and cationic fluorocarbon surfactants Zonyl FSA and FSC and nonionic surfactant octanol on Teflon, contact angle hysteresis is substantially higher than that for pure water. Hydrophobic bonding of the surfactant molecules at the solid—liquid interface appears to be responsible for this change. Although inhomegeneities on the Teflon surface cause the advancing and receding contact angles to vary at a fixed surfactant concentration, their difference displays significantly lower scatter, indicating that hysteresis is a more reproducible material property than the individual contact angles. Experimental dimensionless sessile drop volumes at the critical inclination angle are compared to an analytical prediction by E. B. Dussan. ( J. Fluid Mech. 151, 1 (1985)). For the cationic and anionic surfactant solutions these volumes are between three and four times the prediction from the analysis. This disagreement is especially surprising because the analysis represents a force balance on the drop at the critical configuration, and a reasonable match was obtained for pure liquids by H. V. Nguyen et al. ( J. Colloid Interface Sci. 115, 410 (1987)). For solutions of the weak surfactant 1-octanol, the experimentally observed drop volumes at the critical inclination angle match the analytical predictions, indicating that the surfactant strength has an important bearing on the results. One possible explanation is that as the solid substrate is tilted from the horizontal, the sessile drop morphology is modified and the contact line shape changes from circular to one with parallel sides. Such a change must be accompanied by fluid motion. The presence of strong surfactants imposes some hydrodynamic rigidity to the solution—vapor interface and opposes this movement. Therefore, for a fixed drop volume, the inclination angle required for the drop to achieve its critical shape is greater than that predicted by the analysis.

Spreading of mixed solution of fluorocarbon and hydrocarbon surfactants on oil

The surface tension and the spreading (on oil) properties of the mixed solution of anionic (or cationic) and cationic (or anionic) fluorocarbon and hydrocarbon surfactants have been studied. The anionic-cationic system has a much higher surface activity than the single component ones. The mixed aqueous solution has not only a very low surface tension, but also a very low oil/water interfacial tension, so that it can spread on oil (n-heptane, light kerosene) efficiently. The high surface activity has been attributed to the strong interaction between the surface active ions with opposite charges.