Fluorocarbon polymerizable surfactants: viscometric behavior, micellar polymerization and interactions with associating polymers

 The micellar aggregation of two fluorocarbon surfactants bearing a polymerizable acrylamido group and differing only in the degree of amido substitution (CONH or CONC₂H₅) has been investigated by viscometry. The two surfactants exhibit distinct solution properties with a micellar growth occurring at a much lower concentration for the N-monosubstituted sample which shows in addition a shear thickening and rheopectic behavior. The ability of the latter surfactant to form hydrogen bonding is responsible for this difference in behavior. Micellar copolymerization of acrylamide with these surfactants or with a hydrocarbon analogue gives copolymers with a polysoap-like behavior. The copolymers in aqueous solution show a pronounced intramolecular hydrophobic aggregation expressed by relatively low-viscosity values when compared with those of other hydrophobically modified water-soluble polymers reported in the literature. Surfactant–polymer mixed systems do not show a strong incompatibility between fluorocarbon and hydrocarbon moieties. Received: 24 March 1998 Accepted: 30 June 1998     

Partial molar volume of dodecyltrimethylammonium hydroxide in water and NaOH aqueous solutions

 The partial molar volume of dodecyltrimethylammonium hydroxide in water and aqueous NaOH solutions was measured. The addition of NaOH did not affect either the micellized or the unmicellized molecules. The expansion on micellization is much larger than in dodecyltrimethylammonium bromide systems, which reflects the stronger ionization of the hydroxide surfactant micelles, when compared with that of the bromide amphiphile. Received: 27 October 1997 Accepted: 4 March 1998     

Structure and phase behaviour of the ternary system water, n-heptane and the nonionic surfactant Igepal® CA520

The phase behavior of the system water, n-heptane and the nonionic surfactant Igepal^® CA520 has been studied by visual inspection, high-performance liquid chromatography, polarizing microscopy and freeze-fracture electron microscopy. The phase diagram at 25?°C contains two large homogeneous microemulsion phases, an extended region of a lamellar liquid crystalline structure and some two- and three-phase regions. The oil-rich part of the phase diagram has been investigated by static and dynamic light scattering in order to examine the behavior of the collective diffusion coefficient and the scattering intensity in the presence of increasing concentrations of water, starting from the binary system of n-heptane and Igepal^® CA520. The results suggested that at a very low water content the aggregates of the microemulsion are small. With the exception of this region the structure is bicontinuous.     

Photophysical and viscometric properties of naphthalene-labeled acrylamide/N,N-dimethyl maleimido propyl ammonium propane sulfonate copolymer

 The synthesis, viscometric, and fluorescence properties of a water-soluble zwitterionic sulfobetaine copolymer, poly(ADMMAPS)/NA, are reported. When fluorescent hydrophobes (naphthyl group) are incorporated into the zwitterionic copolymer, the photophysical response may effectively probe solution behavior on the microscopic level. Experimental results indicate that I _E/I _M steadily increases with increases in polymer concentration. I _E/I _M in aqueous solution is greater than that in aqueous potassium chloride solution. Dynamic light scattering (QELS) measurements show that hydrodynamic diameters of the naphthalene-labeled zwitterionic sulfobetaine copolymer increase with an increasing salt concentration. Viscosity studies reveal that the polymer coil expanded as more salt is added. In fluorescence quenching study, the reduction in the quenching efficiency of Tl⁺ with salt addition can arise from enhanced compartmentalization of naphthalene labels as added electrolyte enhances intrapolymer micellization. The intrapolymer micelle is easily formed, indicating that the thallium ion has difficulty reacting with bound naphthalenes located in the polymer coil. The naphthalene-labeled zwitterionic sulfobetaine copolymer is depicted as a compacted polymer coil conformation in deionized water because of intra-and inter-associations. Consequently, salt addition breaks up the associations and enhances the intrapolymer micellization. The microscopic and macroscopic behaviors of zwitterionic sulfobetaine copolymer differ a lot from those of the corresponding cationic copolymer. Received: 4 February 1997 Accepted: 1 May 1997     

Studies on the interactions between anionic surfactants and polyvinylpyrrolidone: Surface tension measurement, 13C NMR and ESR

 The interaction between anionic surfactants and polyvinylpyrrolidone (PVP) are investigated using ¹³C NMR, ESR spectroscopy and surface tension measurements at the air/water interface. The behavior of single-chained surfactant, sodium dodecyl sulphonate (AS), is compared with that of the double-chained surfactant, sodium bis(2-ethylhexyl) phosphate (NaDEHP). The results showed that a surfactant–polymer complex of “necklace and head structure” is formed in AS aqueous solutions in the presence of PVP due to the hydrophobic interaction between PVP and AS. The AS micelles nucleate on the polymer hydrophobic sites, and the mobility of the AS head groups is not affected. But, for NaDEHP surfactant, it was found that PVP is little effective in influencing the monomer–micelle equilibrium and no surfactant– polymer complex formed in the NaDEHP aqueous solution. Received: 8 May 1996 Accepted: 14 August 1997     

A proton NMR study on aggregation of cationic surfactants in water: effects of the structure of the headgroup

 ¹H NMR chemical shifts of solutions of the following cationic surfactants in D₂O were determined as a function of their concentrations: cetyltrimethylammonium chloride, CTACl, a 1 : 1 molar mixture of CTACl and toluene, cetylpyridinium chloride, CPyCl, cetyldimethylphenylam-monium chloride, CDPhACl, cetyldimethylbenzylammonium chloride, CDBzACl, cetyldimethyl-2-phenylethylammonium chloride, CDPhEtACl, and cetyldimethyl-3-phenylpropylammonium chloride, CDPhPrACl. Plots of observed chemical shifts versus [surfactant] are sigmoidal, and were fitted to a model based on the mass-action law. Satisfactory fitting was obtained for the discrete protons of all surfactants. From these fits, we calculated the equilibrium constant for micelle formation, K, the critical micelle concentration, CMC and the chemical shifts of the monomer, δ_mon and the micelle δ_mic. ¹H NMR-based CMC values are in excellent agreement with those which we determined by surface tension measurements of surfactant solutions in H₂O, allowing for the difference in structure between D₂O and H₂O. Values of K increase as a function of increasing the size of the hydrophilic group, but the free energy of transfer per CH₂ group of the phenylalkyl moiety from bulk water to the micellar interface is approximately constant, 1.9±0.1 kJ mol^-1. Values of (δ_mic–δ_mon) for the surfactant groups at the interface, e.g., CH₃–(CH₂)₁₅–N+(CH₃)₂ and within the micellar core, e.g., CH₃–(CH₂)₁₅–N⁺ were used to probe the (average) conformation of the phenyl group in the interfacial region. The picture that emerges is that the aromatic ring is perpendicular to the interface in CDPhACl and is more or less parallel to it in CDBzACl, CDPhEtACl, and CDPhPrACl. Received: 23 February 1996 Accepted: 29 August 1996     

Solubilizing interactions of octylphenol surfactants with liposomes modeling the stratum corneum lipid composition

 The interaction of a series of polyethoxylated octylphenols (ethylene oxide units average 8.5–20.0) with liposomes modeling the stratum corneum (SC) lipid composition (40% ceramides, 25% cholesterol, 25% palmitic acid and 10% of cholesteryl sulfate) was investigated. The surfactant/lipid molar ratios (Re) and the bilayer/aqueous-phase partition coefficients (K) were determined by monitoring the changes in the static light scattering of the system during solubilization. The fact that free concentration for each surfactant tested was always similar to its critical micelle concentration (CMC) indi-cates that the liposome solubilization was mainly ruled by the formation of mixed micelles. The Re and K para-meters for liposome saturation fell as the surfactant HLB increased. Thus, at this interaction step the higher the surfactant HLB, the higher the ability of these surfactants to saturate SC liposomes and the lower their degree of partitioning into liposomes. However, the maximum solubilizing ability was achieved at intermediate HLB values. Thus, the octylphenols with 20 and 12.5 ethylene oxide units showed, respectively, the highest power of saturation and solubilization of SC structures in terms of the total surfactant amounts needed to produce these effects. Different trends in the interaction of these surfactants with SC liposomes were observed when comparing the Re and K parameters with those reported for PC ones. Thus, whereas the SC liposomes were more resistant to the surfactant action, the affinity of these surfactants with these bilayer structures was higher in all cases. Received: 3 March 1997 Accepted: 22 May 1997     

Structure of salted-out, solubilized micelles and microemulsions on the perfluorinated anionic surfactant tetraethylammonium perfluorooctyl sulfonate studied by cryogenic transmission electron microscopy

 Tetraethylammonium perfluorooctyl sulfonate (TEAFOS; critical micelle concentration, 1 mM), which forms a threadlike micelle in its pure solution, was adopted to study the structure of salted-out, solubilized micelles and microemulsions by cryogenic transmission electron microscopy. The concentration of the surfactant was kept constant at 60 mM. The micelle solution salted out with LiNO₃ provided a surfactant phase in the presence of a clear interface. The surfactant phase was studded, being formed of homogeneously dispersed spherical micelles, and had no obvious threadlike forms. The micelles, which solubilized the maximum amount of perfluorinated oil, were spherical and had the same size as isolated spherical micelles in pure TEAFOS solution. The microemulsions were formed in the presence of perfluorinated alcohol as cosurfactant and the particles were rotund even when the concentration of the perfluorinated oil was equivalent to that for solubilization and the sizes increased with increasing oil content. The difference in size between the solubilized micelles and microemulsions with the same amount of oil suggested that the oil molecules had been solubilized between palisades of perfluorinated alkyl chains in the micelles and had dissolved in the cores of the microemulsions. Received: 10 September 1999/Accepted: 2 December 1999     

Apparent molar volume and apparent molar adiabatic compressibility of 2-hydroxy-5-methyl acetophenone in <Emphasis Type="Italic">N,N</Emphasis>-dimethylformamide at different temperatures

The speed of sound and density of 2-hydroxy-5-methyl acetophenone in dimethylformamide have been measured over the range of temperatures 25–40 °C. From the experimentally determined data, values of apparent molar volume (V _ϕ), adiabatic compressibility (β_s), apparent molar adiabatic compressibility (K _s,ϕ) and their limiting values have been computed. Values at infinite dilution provide information regarding solute–solvent interaction. The density and velocity increases with increase in concentration and decreases with increase in temperature. These results have been analyzed in terms of molecular interactions between acetophenone and dimethylformamide.     

Phase behaviour and physical properties of the cationic quaternary system tetradecyldimethylamine oxide hydrochloric acid 1-hexanol water

 The phase behaviour and properties of the tetradecyldimethylamine oxide/HCl/hexanol/water quaternary surfactant system have been studied by means of electric conductivity, rheology, freeze-fracture transmission electron microscopy (FF-TEM) and small-angle neutron scattering (SANS). In this system the originally zwitterionic surfactant can become increasingly charged by protonation through the addition of HCl, i.e. the degree of charging can be changed continuously. An interesting, isotropic phase (L₁ ^* phase) of low viscosity was observed for intermediate degrees of charging. From viscosity and conductivity measurements this phase can clearly be distinguished from the conventional L₁ phase that is composed of micelles. Investigation of the structures present by means of FF-TEM and SANS showed that the L₁ ^* phase is made up of unilamellar vesicles of extremely small diameter of 8–10 nm. Evidently such highly curved structures are stabilized by the electrostatic conditions in this system. Received: 11 July 1999/Accepted: 25 August 1999     

Reactive surfactants in heterophase polymerization: Colloidal properties,film‐water absorption,and surfactant exudation

In this article the results obtained with latexes prepared by emulsion polymerization with a conventional surfactant and a polymerizable surfactant (surfmer) are presented. For this study, well‐defined styrene‐butylacrylate latexes with a conventional nonreactive surfactant (sodium dodecyl sulfate) and a maleate diester surfmer, of which films can be easily cast, were used. The latex with the surfmer was prepared following a surfmer addition strategy to maximize the amount of surfmer bound to the particle surface, and not buried in the particle interior. The latex properties in terms of mechanical stability, film‐water absorption, and film‐surfactant exudation were assessed and compared. The mechanical stability and water‐absorption properties of the latex prepared with surfmer were better than those of the latex with sodium dodecyl sulfate. Additionally, by using a surfmer the surfactant migration to the film‐substrate and film‐air interfaces can be inhibited. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2994–3000, 2002     

Investigation on the basic hydrolysis of crystal violet in mixed reverse micelles formed with AOT and nonionic surfactants

 The kinetics and thermodynamics of the basic hydrolysis of crystal violet (CV) in mixed reverse micelles formed with anionic surfactant AOT and nonionic surfactants have been investigated. It was found that the mixed reverse micelles had inhibitory effects on CV hydrolysis compared with the normal aqueous solution, and the equilibrium constant K of the reaction in mixed reverse micellar systems is smaller than that in pure water. The influence of water content and surfactant composition in reverse micelles on the second-order rate constant k ₁ of the positive reaction, on the first-order rate constant k _-1 of the reverse reaction, as well as on the equilibrium constant K of the reaction has been studied, and the results obtained were interpreted in terms of the nature of surfactants and the properties of microenvironment where the reaction took place. Received: 24 October 1997 Accepted: 18 March 1998     

Rheological properties and structures of cationic surfactants and fatty alcohol emulsions: effect of surfactant chain length and concentration

 Rheological and optical properties of cetyltrimethylammonium chloride (CTAC)/fatty alcohol (FA), behenyltrimethylammonium chloride (BTAC)/FA and CTAC/FA/hydroxyethyl cellulose (HEC) emulsions have been studied with particular emphases on the effects of FA content, the difference in the chain length of the hydrophobic groups between CTAC and BTAC, and the addition of a water soluble polymer, HEC. The effects of the FA content are to accelerate the structure development during the aging period and to increase the storage modulus, the yield stress, and the zero-shear-rate viscosity in the three emulsion systems investigated. At a low FA content of 2% w/w, lamellar and vesicular aggregates and isolated multilamellar vesicles can be observed in the CTAC/FA and BTAC/FA emulsions, respectively. At a high FA content of 6% w/w or with an excess of FA present, networklike structures and sunflower-like structures form, respectively, instead, inducing a higher entanglement storage modulus and a higher yield stress relative to those emulsions with a low FA content. The effect of adding HEC to the CTAC/FA emulsion is to reduce the entanglement storage modulus and the yield stress, consistent with the optical observation that the presence of the polymer disrupts the formations of lamella and vesicular aggregates and network structures. Received: 27 July 2000 Accepted: 28 November 2000     

Conductivity,apparent molar volume and isentropic compressibility of 12-tungstosilicic acid and potassium 12-tungstosilicate in aqueous solutions at different temperatures

12-Tungstosilicic acid and potassium 12-tungstosilicate were synthesized and conductivities, densities and ultrasound velocities of their aqueous solutions were studied in the 283.15–303.15 K temperature range at 5 K intervals. Apparent molar volume and apparent molar isentropic compressibility of 12-tungstosilicic acid and potassium 12-tungstosilicate and isentropic compressibility of the studied aqueous solutions have been determined from the experimental density and sound velocity data.     

Apparent molar volume, isentropic compressibility and conductivity of di-sodium hydrogen phosphate in water and in aqueous solutions of 1-propanol

Precise measurements on the density and sound velocity of solutions of di-sodium hydrogen phosphate in 1-propanol + water mixed-solvent media with alcohol mass fractions of 0.00, 0.05, 0.10 and 0.15 are reported in the 283.15–303.15 K temperature range at 5 K intervals. Electrical conductivity and refractive index of the solutions are studied at 298.15 K. From the experimental density and sound velocity data, the apparent molar volume and isentropic compressibility values of di-sodium hydrogen phosphate have been evaluated. The results show a positive transfer volume of di-sodium hydrogen phosphate from an aqueous 1-propanol solution to a more concentrated 1-propanol solution. The apparent molar isentropic compression of di-sodium hydrogen phosphate in aqueous 1-propanol solutions is negative and it increases with increasing the concentration of 1-propanol and temperature. The negative values of apparent molar isentropic compression imply that the water molecules around the di-sodium hydrogen phosphate are less compressible than the water molecules in the bulk solutions. The effects of the electrolyte concentration and relative permittivity of the medium on the molar conductivity were also investigated.     

Quantification of H, B and F in Kornerupine: Accuracy of SIMS and SREF (X-Ray Single-Crystal Structure-Refinement) Data

 We use a multiple-analytical approach based on secondary-ion mass-spectrometry (SIMS), X-ray single-crystal structure refinement (SREF) and electron-probe micro-analysis (EPMA) to derive the complete crystal-chemical formula of a B-rich kornerupine-group mineral, prismatine, from Hrarigahy, Madagascar: (Ca_0.01Li_0.02Mg_0.20Fe²⁺ _0.10) (Mg_3.57Fe²⁺ _0.06 Al_5.37) (Si_3.84B_0.91Al_0.26)O₂₁ (OH_1.08F_0.07). SIMS matrix effects related to crystal structure were investigated by analyzing two grains with a known crystallographic orientation relative to the ion beam. Boron orders at the T3 site. The refined site-scattering for T3, 6.33 eps (electrons per site) agrees well with the mean bond-length for this site (1.512 ?), which indicates nearly complete occupancy by B (85% rel.). B₂O₃ (∼ 4 wt%), derived by SREF, agrees with the SIMS data within analytical uncertainty using Si as the inner reference for the matrix. The occupancy of the X site obtained by combining the SIMS and EPMA data (5.30 eps; electrons per site) agrees with the refined site-scattering value (5.75 eps). Trace quantities of Li and Ca are ordered at this site. SIMS data for H₂O is in accord with the stoichiometric value, indicating complete occupancy at O10 by OH. Fluorine (∼ 0.17 wt%) orders at O10: it corresponds to ∼ 0.07 atoms per formula unit (apfu) vs. 0.15 apfu (atoms per formula unit) by SREF, indicating a slight overestimation of F with SREF, as previously observed in fluoborite. Our data show that SIMS chemical matrix effects are well-calibrated, and emphasize the usefulness of independent micro-analytical techniques in testing the mutual accuracy and consistency of experimental data.     

Kinetics of alkaline fading of methyl violet in micellar solutions of surfactants: Comparing Piszkiewicz's,Berezin's,and pseudophase ion-exchange models

The micellar effect of surfactants of various types on the rate of the reaction between methyl violet and hydroxide ion is studied. The absorption spectra show that the cation of methyl violet is bound by micelles of all types at proper concentrations of surfactants. The observed rate constant in micellar systems containing nonionic Brij-35, zwitterionic 3-(dimethyldodecylammonio)-propanesulfonate, cationic cetyltrimethylammonium bromide and hydroxide surfactants is higher, whereas in solutions of the anionic surfactant sodium dodecylsulfate is lower than that one in the surfactant-free system. Piszkiewicz's, Berezin's, and pseudophase ion-exchange models of the kinetic micellar effect are used for the treatment of the dependences of the above-mentioned constants on the surfactant concentration. The values of the corresponding kinetic parameters are compared and discussed. The influence of nonionic, zwitterionic, and anionic micelles on the reaction rate is discussed on the basis of medium and concentration kinetic effects. The character of the cationic micelles effect is somewhat paradoxical. Although the observed pseudo–first-order reaction rate constant substantially increases in the presence of such micelles, the second order-rate constant in these micelles is lower than the corresponding value in surfactant-free aqueous solution. As a possible explanation, the decrease in the reactivity of the HO^– ions is proposed, owing to their electrostatic association with the cationic headgroups (“diverting effect”).     

Contribution to the certification of B, Cd, Mg, Pb, Rb, Sr, and U in a natural water sample for the International Measurement Evaluation Programme Round 9 (IMEP-9) using ID-ICP-MS

 The present paper describes the contribution of the Institute for Reference Materials and Measurements to the certification of B, Cd, Mg, Pb, Rb, Sr, and U amount contents in a natural water sample, in round 9 of the International Measurement Evaluation Programme (IMEP-9). The analytical procedure to establish the reference values for B, Cd, Mg, Pb, Rb, Sr, and U amount contents was based on isotope dilution inductively coupled plasma-mass spectrometry used as a primary method of measurement. Applying this procedure reference values, traceable to the SI, were obtained for the natural water sample of IMEP-9. For each of the certified amount contents presented here a total uncertainty budget was calculated using the method of propagation of uncertainties according to ISO and EURACHEM guidelines. The measurement procedures, as well as the uncertainty calculations are described for all seven elements mentioned above. In order to keep the whole certification process transparent and so traceable, the preparations of various reagents and materials as well as the sample treatment and blending, the measurements themselves, and finally the data treatment are described in detail. Explanations focus on Pb as a representative example. The total uncertainties (relative) obtained were less than 2% for all investigated elements at amount contents in the pmol/kg up to the high μmol/kg range, corresponding to low μg/kg and mg/kg levels. Received: 21 October 1999 / Accepted: 29 January 2000