The Effects of Alcohol with Different Chain Length on the Phase Equilibria of Nonionic Surfactant System

Addition of alcohol with longer chain length (C₆H₁₃OH, C₈H₁₇OH, and C₁₂H₂₁OH) caused a reduction the cloud point of a commercial nonionic surfactant, Tesgitol (T_15-s-9). The formation of lamellar liquid crystal (LLC) was favored so that isotropic liquid (L₁)-LLC two-phase region became wider with increasing temperature at an appropriate weight ratio of surfactant to alcohol. The isotropic liquid phase/liquid two phase transformation was replaced by a two-phase transformation to isotropic liquid/lamellar liquid crystal at the cloud point for the system without alcohol.     

Striking differences between alkyl sulfate and alkyl sulfonate when mixed with cationic surfactants

The properties of alkyl sulfate and alkyl sulfonate are similar except for their Krafft points. However, alkyl sulfate and alkyl sulfonate behave quite differently when they are mixed with cationic surfactants and show some totally unexpected results. In this work sodium alkyl sulfate (C_nH_2n+1SO₄Na,C_nSO₄)–alkyl quaternary ammonium bromide [C_nH_2n+1N(C_mH_2m+1)₃Br, C_nN, m=1–4] mixtures and sodium alkyl sulfonate (C_nH_2n+1SO₃Na, C_nSO₃)–C_nN mixtures were studied. It was found that, in contrast to the single surfactants, C_nSO₃–C_nN mixtures were much more soluble than C_nSO₄–C_nN mixtures. Besides, the two kinds of catanionic surfactant mixtures were quite different in their phase behavior and aggregate properties. The results were interpreted in terms of the interactions between surfactant molecules, which were very different in the two kinds of mixed systems owing to the distinction between alkyl sulfate and alkyl sulfonate in the molecular charge distribution.     

Effect of Organic Solvents on the Electrodeposition of Copper from Acidified CuSO4

Using Guerbet tetradecyl alcohol C₁₄GA (synthesized by Guerbet reaction using 1-heptanol as raw material) as intermediate, sodium Guerbet tetradecyl polyoxyethylene ether sulfates [C₁₄GA(EO)_nS, n = 1, 2, 4] were obtained through following steps: synthesizing Guerbet tetradecyl polyoxyethylene ether alcohols [C₁₄GA(EO)_nH, n = 1, 2, 4] by Williamson reaction, then esterifying with chlorosulfonic acid so as to form Guerbet tetradecyl polyoxyethylene ether alcohol sulfates [C₁₄GA(EO)_nSO₃H, n = 1, 2, 4], and finally neutralizing with sodium hydroxide; while sodium Guerbet tetradecyl sulfate(C₁₄GAS) was synthesized only through esterifying and neutralizing reactions. The structures of these anionic surfactants were determined by infrared, nuclear magnetic resonance, and element analysis. The surface activity of these surfactants was studied by means of surface tension. The results have shown that these surfactants possess higher surface activity than the common surfactant C₁₂H₂₅OSO₃Na. Branched-tail structure coming from Guerbet alcohol makes the anionic surfactant (C₁₄GAS) have higher critical micelle concentration (CMC) and better effectiveness in lowering the interface tension between air and water than their linear counterpart (C₁₄H₂₉OSO₃Na). Introducing oxyethyene group into the place between head group and tail group of the surfactant molecule with branched tail can lower the CMC, γ_cmc, and Krafft point. And the effectiveness for reducing the CMC, γ_cmc, Γ_max, and Krafft point of surfactant increased with the increase of oxyethylene group number (n = 1, 2, 4). The relationship between the molecular structure and surface activity of surfactant is discussed.     

Cationic–anionic fluorinated surfactant mixtures based on short fluorocarbon chains as potential aqueous film-forming foam

A strategy for aqueous film-forming foam (AFFF) using cationic-anionic surfactant mixtures with short fluorocarbon chains (≤C₄) in both cationic and anionic surfactants was proposed. The minimum surface tension (γ_min) of mixtures of C₄F₉SO₂NH(CH₂)₃N(CH₃)₃I (C₄FI) and C_nF_2n+1COONa (n?=?1, 2, 3, 4) with different molar ratios (5:1, 2:1, 1:1, 1:2, 1:5) was measured at 25?°C. The γ_min for all mixtures of C₄FI–C_nF_2n+1COONa were remarkably lower than that of pure C₄FI. Among these mixtures, the equimolar mixture of C₄FI–C₃F₇COONa was chosen because of the low γ_min, qualified solubility and relatively high fluorine efficiency. The spreading coefficients of its aqueous solution on n-heptane, toluene, benzene, cyclohexane and gasoline were all positive, indicative of its potential in AFFF. The film spreading, sealability and foaming were also tested. The influences of ‘green’ additives (alkyl glucose amide, xanthan gum and sodium carboxymethylcellulose) on foaming performance were studied, in which small dosage of xanthan gum could greatly retard the drainage of foam. It was confirmed that the mixing of oppositely charged surfactants both possessing short fluorocarbon chains was a valuable thought to design AFFF. In application, the quaternary ammonium surfactant likewise can be bromide or chloride rather than iodide for reasons of cost-reduction and stability.     

Über das Phasenverhalten ternärer Systeme des Typs H2O-Öl-Nichtionisches Tensid

This paper deals with the change of the phase diagram of ternary systems of the type H₂O-oil-nonionic surfactant with temperature, in particular, with the question regarding the reasons for the separation of such mixtures into three phases. It is shown that the phase behavior is mainly determined by the interplay between the lower miscibility gap between oil and surfactant with the upper miscibility gap between H₂O and surfactant. From systematic investigations with dodecane, octane, cyclohexane and toluene as oils with ?simple“ alkylpolyethyleneglycolethers C_iE_j as surfactants, ten qualitative rules are derived concerning the dependence of the position and the width of the three-phase temperature interval on the hydrophobicity of the oil and the amphiphilicity of the surfactant. The rules permit the choice of the appropriate surfactant for application in chemical engineering. Finally, the phase behavior with mixtures of oils and mixtures of surfactants, resp., is studied.     

Thermal properties of ternary systems: The calculation of the standard enthalpy of solution for compounds in binary mixtures

An equation free of fitting parameters is proposed for calculating the standard heats of solution for compounds in nonaqueous binary mixtures. The parameters of the equation are the standard heats of solution of a compound in the components of the mixed solvent. Nonlinear ΔH ⁰(x) trends are reconstructed for solutions of water in i-PrOH + MeOH and MeCN + MeOH, t-BuOH in MeCN + MeOH, squalane in CHCl₃ + CCl₄ and C₆H₆ + CHCl₃, and hexadecane in MeOH + i-Pr₂O and in mixtures of butyl acetate, ethyl acetate, and 1,4-dioxane with 1-octanol. The standard heats of solutions are calculated for water in alcohol + alcohol, alcohol + aprotic solvent, and aprotic solvent + aprotic solvent mixtures     

Improved direct electron transfer and electrocatalytic activity of horseradish peroxidase immobilized on gemini surfactant–polyvinyl alcohol composite film

The voltammetric and electrocatalytic behavior of horseradish peroxidase (HRP) immobilized on a cationic gemini surfactant (i.e. C₁₂H₂₅N(CH₃)₂–C₁₂H₂₄–N(CH₃)₂C₁₂H₂₅Br₂, C₁₂–C₁₂–C₁₂)–polyvinyl alcohol (PVA) composite film-coated glassy carbon electrode (GCE) has been studied. It is found that on the novel composite film HRP presents excellent electroactivity and can exhibit a pair of well-defined voltammetric peaks in 0.10 M pH 7.0 phosphate buffer solution (PBS). The immobilized HRP also presents good bioelectrocatalytic activity, and it can catalyze the reduction of oxygen (O₂), hydrogen peroxide (H₂O₂), nitrite ion (NO₂^?) and trichloroacetic acid (TCA). For H₂O₂ the catalytic current is linear to its concentration in the range of 0.195–97.5 μM, and the detection limit is down to 6.5 × 10^?8 M. The response shows Michaelis–Menten feature and the apparent Michaelis–Menten constant is estimated to be 110.5 μM. Similarly, the electrode can sense NO₂^? and TCA. In addition, it is observed that the spacer group of gemini surfactant affects the electroactivity of HRP significantly. A spacer group with higher flexibility and hydrophility is favorable to the electron transfer of HRP. UV–vis spectrum indicates that the structure of HRP in the PVA–C₁₂–C₁₂–C₁₂ film is similar to that of native HRP. Thus the C₁₂–C₁₂–C₁₂–PVA composite possesses good biocompatibility and has promising application in fabricating biosensor and bioelectronics.     

Active Sites Decorated Nonpolar Pore-Based MOF for One-step Acquisition of C2H4 and Recovery of C3H6

Herein, a 2-fold interpenetrated metal-organic framework (MOF) Zn-BPZ-TATB with accessible N/O active sites in nonpolar pore surfaces was reported for one-step C₂H₄ purification from C₂H₆ or C₃H₆ mixtures as well as recovery of C₃H₆ from C₂H₆/C₃H₆/C₂H₄ mixtures. The MOF exhibits the favorable C₂H₆ and C₃H₆ uptakes (>100 cm³ g⁻¹ at 298 K under 100 kPa) as well as selective adsorption of C₂H₆ and C₃H₆ over C₂H₄. The C₃H₆- and C₂H₆-selective feature were investigated detailedly by experimental tests as well as sorption kinetic studyies. Molecular modelling revealed the multiple interactions between C₃H₆ or C₂H₆ molecules and methyl groups as well as triazine rings in pores. Zn-BPZ-TATB not only can directly generate 323.4 L kg⁻¹ and 15.4 L kg⁻¹ of high-purity (≥99.9 %) C₂H₄ from C₃H₆/C₂H₄ and C₂H₆/C₂H₄ mixtures, but also provide a large high-purity (≥99.5 %) C₃H₆ recovery capacity of 60.1 L kg⁻¹ from C₃H₆/C₂H₄ mixtures. More importantly, the high-purity C₃H₆ (≥99.5 %) and C₂H₄ (≥99.9 %) with the productivities of 38.2 and 12.7 L kg⁻¹ can be simultaneously obtained from C₂H₆/C₃H₆/C₂H₄ mixtures through a single adsorption/desorption cycle.     

KINETIC EFFECTS OF SURFACTANT / POLYMER MIXTURES UPON ACIDIC HYDROLYSIS OF HYDROXAMIC ACIDS

The influence of surfactant / polymer (polyethylene glycol, PEG, mol. wt. = 400) mixtures upon the acidic hydrolysis of two N-substituted hydroxamic acids, i.e., R(CO). N(OH)R' : R = C₆H₅, R' = C₆H₅;4-CH₃C₆H₄ has been studied using cationic (CTAB, TTAB and CPC) and nonionic (TX-100 and Brij-35) surfactants. An inhibitory effect was observed. The results have been explained by Porinoy - Menger model. The critical aggregation concentration and polymer saturation point of the corresponding systems have also been measured with the conductivity and surface tension methods.     

The Influences of Polymers and Temperature on the Foam Properties of 3‐Dodecylalkoxyl‐2‐hydroxylpropyl Trimethylammonium Chloride

The foam performances of 3‐dodecoxy‐2‐hydroxypropyl trimethylammonium chloride (C₁₂TAC) have been determined in the existence of different relative amount of polymer. The experimental results show that the foaming ability of the mixture systems of the C₁₂TAC/PEG and C₁₂TAC/PVP is stronger than that of the surfactant solutions in the absence of polymer, and with the increase of relative amount of polymer both foaming efficiency and foam stability of the surfactant solutions are evidently enhanced. For the aqueous solution of the surfactant, effect of temperature on foaming properties has also been examined. The results show that both the foaming ability and stability of the foams of the surfactant solutions are highest (or strongest) at 30°C.     

Investigation of aqueous foam stability containing pigment colorant using polyoxyethylene nonionic surfactant

To improve foam stability in pigment foaming dispersions, a series of fatty alcohol polyoxyethylene ether (CmEOn) with different alkyl chain and ethylene oxide (EO) chain length (m = 12, 14, 16 and n = 5, 7, 9) were used as foam stabilizer to select the most superior structure for stabilizing foam. The effects of CmEOn on surface tension were investigated which revealed that the CMC of CmEOn in the pigment foaming dispersion decreased with the increase of surfactant hydrophobicity or the decrease of hydrophilicity. Compared to the alkyl chain, EO chain length influenced foam more significantly. C₁₄EO₅ in the pigment foaming dispersion showed lowest CMC and equilibrium surface tension. The presence of wormlike micelles and lamellar liquid crystal of SDS and C₁₄EO₅ endowed the C₁₄EO₅ pigment foaming dispersion with highest viscosity which was distinctly different with other CmEOn. C₁₄EO₅ showed the most superior stabilization effects with foam half-life of 172.9 min at 9 wt%. To further analyze the stabilization mechanism of C₁₄EO₅, the foam volume and bubble diameter change were observed with a digital microscope. The results demonstrated that the superior stabilization effects of C₁₄EO₅ were closely related to its high viscosity, which mainly resulted in the decrease of foam drainage and gas permeability. C₁₄EO₅, the optimal CmEOn structure for stabilizing foam, shows excellent foam stabilization capability in pigment foaming dispersions, which is a promising tool to realize pigment foam coloring.     

Influence of ethyl alcohol in the preparation, morphology and properties of compound DAS–Eu3+ and its thermal degradation products

In this study, two compounds presenting characteristics different from each other were produced from there action between hydrated Eu³⁺ sulfate and Ba²⁺ diphenylamine-4-sulfonate using, respectively, aqueous solution for producing the Eu(C₁₂H₁₀NSO₃)₃·7H₂O (A) compound and water/ethyl alcohol (7:1) solution for the Eu(C₁₂H₁₀NSO₃)₃·5H₂O (B) production. The presence of alcohol molecules in the solution will interfere in the structural arrangement of anionic surfactant DAS^? (diphenylamine-4-sulfonate) around the metal ions Eu³⁺ allowing differentiation in the stoichiometric formulas, morphology, and thermal properties of these compounds and their derivatives. Thus, when treating both compounds under oxidizing atmosphere, we found different temperatures of the water loss and conversion of the intermediate pair oxydisulfate [Eu₂O(SO₄)₂]/dioxysulfate [(Eu₂O₂SO₄)]. However, the effect of water/surfactant/alcohol interactions in the metal ion structural arrangement becomes still more evident under reducing atmosphere. After this thermal treatment, significant changes were observed in the morphological characteristics and physical properties of the (Eu₂O₂S oxysulfide) in compound B with respect to compound A.     

Influence of polyvinylalcohol on the solvation volumes of FeCl<Subscript>3</Subscript> and CoCl<Subscript>2</Subscript> in aqueous ethanol solutions

The effect of polyvinylalcohol (PVA) on molar, Van-der Waals and the electrostriction volumes of FeCl₃ and CoCl₂ in pure H₂O and 50% ethanol (EtOH)–water mixtures was studied. Excess volumes were also calculated and their values were discussed in terms of Pierotti theory (Scaled Particle Theory). Different theoretical energy values were calculated to explain the following parameters: volumes, dispersion, induction energies and 6-12 Lennard–Jones parameters. The increase and the decrease in excess volumes of FeCl₃, CoCl₂ in the absence and in the presence of polyvinyl alcohol in both aqueous and 50% EtOH–H₂O mixtures were also discussed in terms of the increase or decrease of different interaction energies.     

Thermodynamic and Dynamic Properties of Micellar Aggregates of Nonionic Surfactants with Short Hydrophobic Tails

The densities and viscosities of binary aqueous mixtures of poly(ethylenoxide)hexanols [C₆H₁₃(OCH₂CH₂)_mOH, C₆E_m] (m= 3, 4, and 5) have been studied in the micellar composition range. For the same surfactants the self-diffusion coefficients in mixtures with heavy water have been determined by the spin-echo pulsed field gradient method. The volumetric data are interpreted by means of the phase separation model, and values of the CMC, volume change, and standard free energy change of micellization are obtained. From the viscosity data the hydration numbers of the surfactant hydrophilic head in the micellar state are computed; they are in agreement with those obtained from HDO self-diffusion data. The surfactant self-diffusion data are used to calculate the apparent micelle radius and the aggregation number. The micellization parameters obtained for the different surfactants are compared and discussed.     

Small angle neutron scattering study of alkyl polyoxyethylene sulfate micelles. Sodium dodecyl-(oxyethylene)2 sulfate in D2O-H2O mixtures at 25°C

SANS data have been obtained for C₁₂H₂₅ (OC₂H₄)₂SO₄ Na. Results have been obtained for i) a series of solutions of variable concentration of the surfactant, ii) an approximately 0.07 M surfactant concentration to which variable amounts of NaCl were added, iii) a series of solutions 0.058M in surfactant but in different D₂O-H₂O mixtures. The SANS data can be described in terms of a model of monodispersed hard spheres interacting via a screened Coulombic potential. The micelles seem to be able to tolerate substantial amounts of salt without changing the internal structure.     

Formation and coexistence of the micelles and vesicles in mixed solution of cationic and anionic surfactant

In the aqueous mixtures of sodium alkylcarboxylate and alkyltrimethylammonium bromide, large unilamelar vesicles can be formed spontaneously or by sonication as the total carbon number in the HC chains is 19 (or larger). Vesicle formation can be influenced by changes of pH, molar ratio of the two surfactant components, and the polar head group of cationic surfactant. Micelles may coexist with the vesicles in these mixed systems. The larger hydrodynamic radius (200 nm) and aggregation number (800) illustrate that the shape of the micelle in 1:1 C₉H₁₉COONa–C₁₀H₂₁N(CH₃)₃Br is rod-like. In some mixed systems, the micelles can be transformed into stable vesicles by sonication — a phenomenon revealed for the first time. The surface-chemical properties of these catanionic surfactant solutions and the stabilities of vesicle have been studied systematically.     

Effect of surfactant adsorption time on the observation of Newton black film in foam film

Observation of Newton black film (NBF) in foam film is possible only with a certain probability W which depends on the concentration C of surfactant in the solution and on the time t_a during which adsorption of surfactant at the solution/air interface has taken place. In the paper, the W(C,t_a) dependence is derived and used to analyze the effect of t_a on the critical surfactant concentration C_c below which NBF in foam film practically cannot be observed. An expression for the C_c(t_a) function is obtained which reveals that C_c decreases substantially with increasing t_a. This expression is found to describe well experimental C_c(t_a) data for foam films obtained from aqueous solution of the therapeutic surfactant INFASURF.     

Micelle formation of a cationic surfactant in the presence of 1,n-alkanediol and the miscibility of alcohols in micelles

Micelle formation of dodecyltrimethylammonium bromide (DTAB) was examined in the presence of α,ω-alkanediols applying conductivity measurements. Octanediol and hexanediol promoted the formation of mixed micelles of DTAB and the alcohol, but butanediol interfered with micellization. Analysis of the critical micelle concentration (cmc) based on the lattice model for mixed solution with the Bragg–Williams approximation indicated an unfavorable interaction between alcohol and water and a favorable interaction between the alcohol and surfactant, with the exception of butanediol. The exchange energy between alcohol and water was 0.5kT higher for alkanediol (C_2n(OH)₂) than for the corresponding regular alcohol (C_nOH), which is believed to have resulted from the smaller mixing entropy for the alkanediol than for the corresponding regular alcohol. It was inferred from the analysis that the cmc increase for C₄(OH)₂ was caused by favorable interaction with water but unfavorable interaction with the micellar surfactant.     

Influence of the Structure of Nonionic Surfactants and the Length of Alkyl Substituents of Calix[4]resorcinarenes on Their Solubility, Acid–Base, and Complexation Properties

Regularities of solubilization of calix[4]resorcinarenes (H₈L) with the variable length of hydrophobic radicals (R = CH₃, C₃H₇, C₅H₁₁, C₇H₁₅, C₈H₁₇, C₉H₁₉, C₁₁H₂₃) by the micelles of nonionic surfactants Triton X-100 and Triton X-405 in aqueous solutions were studied using solubility measurements. It was found that the solubilization capacity of surfactant micelles with respect to H₈L and [H₄L]^4– depends on the extension (thickness) of their polar layers. It was shown by means of potentiometric titration that, in solutions of nonionic surfactants, the constants of the interaction between tetraanions [H₄L]^4– and tetrametylammonium ions depend on the structure and concentration of nonionic surfactants and the hydrophobicity of H₈L molecules. A change in the affinity of the [H₄L]^4– anions for protons and tetramethylammonium cations in nonionic surfactant solutions was revealed in relation to the length of substituents R and reagent concentrations.     

Studies on the Physicochemical Properties of 3-Alkoxyl-2-hydroxypropyl Trimethylammonium Chloride–Sodium Dodecyl Sulfonate Binary-Surfactant Aqueous Systems

Surface tension, micelle formation, surface adsorption, and solubilization of dimethylaminoazobenzene (DMAB) are studied in aqueous solutions of 3-alkoxyl-2-hydroxypropyl trimethylammonium chloride (alkoxyl = C_nH_2n+1O, n = 8, 12, 14, 16), of sodium dodecyl sulfonate, and of mixtures of these cationic surfactants and the anionic surfactant at 40°C. Synergistic effects on micelle formation, surface tension reduction, and solubilization enhancement of DMAB are observed in the cationic–anionic mixed surfactant systems. The experimental results are discussed in the light of the interactions between the two kinds of surfactant ions.