Synthesis and Surface Properties of Novel Cationic Gemini Surfactants

A series of novel cationic gemini surfactants, p-[C _n H_2n+1N⁺(CH₃)₂CH₂CH(OH)CH₂O]₂C₆H₄·2Cl^? [A(n = 12), B(n = 14) and C(n = 16)], containing a spacer group with two flexible and hydrophilic groups (2-hydroxy-1,3-propylene) on both sides of a rigid and hydrophobic group (1,4-dioxyphenylene) has been synthesized by the reaction of hydroquinone diglycidyl ether with N,N-dimethylalkylamine and N,N-dimethylalkylamine hydrochloride. Their surface-active properties have been investigated by surface tension measurement. The critical micelle concentration (cmc) values of the synthesized cationic gemini surfactants are one order of magnitude lower than those of their corresponding monomeric surfactants (C _n H_2n + 1N⁺(CH₃)₃·Cl^?). Both the cmc and surface tension at the cmc (γ_cmc) of A are lower than those of p-[C₁₂H₂₅N⁺(CH₃)₂CH₂]₂C₆H₄·2Cl^? (D). The novel cationic gemini surfactants A and B also show good foaming properties.     

Ternary diffusion coefficients of diethanolamine and N-methyldiethanolamine in aqueous solutions containing diethanolamine and N-methyldiethanolamine

Ternary diffusion coefficients of diethanolamine (DEA) and N-methyldiethanolamine (MDEA) in aqueous solutions containing DEA and MDEA using the Taylor dispersion technique have been measured for temperatures (303.2, 313.2, and 323.2 K). The systems studied were aqueous solutions containing total amine concentrations of 2.5 and 4.0 kmol m⁻³, each having four different amine molar ratios. The density and viscosity of the blended amine solutions were also measured. The mutual diffusion coefficients of aqueous DEA and aqueous MDEA solutions were also reported. The main diffusion coefficients (D₁₁ and D₂₂) and the cross-diffusion coefficients (D₁₂ and D₂₁) were reported as function of temperature and concentration of alkanolamines. The limiting conditions for the main diffusion coefficients and the cross-diffusion coefficients were discussed at first, and a comparison between the ratios of the cross-diffusion coefficients to the main diffusion coefficients for DEA and MDEA was made. The dependence of the main diffusion coefficients on the viscosity of solutions was also investigated.     

Synthesis and Surface Activity of Anionic Gemini Surfactants with Alkyl Spacers

A series of anionic Gemini surfactants called alkanediyl-α,ω-bis(m-octylphenoxy sulfonate) with different length of (CH₂)_x spacer, C₈C_xC₈ (x = 2, 4, 6, 8), have been synthesized from 4-n-octylphenol and their basic physicochemical properties are investigated. The results indicate that they are different from cationic Gemini surfactants called alkanediyl-α,ω-bis(dimethyldodecylammonium bromide), 12-(CH₂)_s-12, in the literature. It is found that as the carbon atom number of the spacer increases, the cmc (critical micelle concentration) decreases gradually, and the surface area per molecule (A_min) decreases initially and then increases. The breakpoints appear at number 4 of carbon atom in the spacer. Though the length of the spacer is different for the Gemini surfactants from C₈C₂C₈ to C₈C₆C₈, there is no obvious change on the micropolarity.     

Solubilization and Transfer Free Energy of Some Organic Compounds from Bulk Aqueous Phase to Micelle of a New Type of Surfactant

A new type of surfactant, 3‐alkoxyl‐2‐hydroxylpropyltrimethyl ammonium bromide (C_nH_2n+1OCH₂CH(OH)CH₂N(CH₃)₃ ⁺Br^?, abbreviated as R_nTAB, n=8, 12, 14, 16) was synthesized. The solubilization of n‐pentanol, n‐hexanol, n‐heptanol, benzyl alcohol, n‐hexane, benzene, toluene, heptane, and carbon tetrachloride in aqueous solutions of R_nTAB, sodium dodecyl sulfonic(R₁₂SO₃N_a), and in the mixed solution of R₁₆TAB/R₁₂SO₃N_a have been studied by the microtitration method. The experimental results show that the solubilized amounts of the organic compounds increase with the growing of the hydrocarbon chain of R_nTAB, and the solubilizing ability of the binary system is lower for polar substances than for a mono‐surfactant aqueous solution. “V” isothermal curves of the solubilized amount of polar substances have been observed, and the minimum solubilized amount is at the molar ratio 1∶1 of R₁₆TAB/R₁₂SO₃N_a. However, the solubilizing ability of mixed surfactants for non polar substances is higher than that for a mono‐surfactant solution, the solubilizing isotherm curves present a “saddle” shape, and the maximum solubilized amount is at the molar ratio 1∶1 of R₁₆TAB/R₁₂SO₃N_a too. The length of hydrophobic chains of surfactant and the polarity of the organic compound affect the transfer free energy from aqueous to micelle phase. The longer the hydrophobic chain of R_nTAB and the lower the polarity of the organic compound, the more easily will the compound transfer from aqueous phase to micelle phase.     

Surfactant Diffusion Near Critical Micelle Concentrations

Taylor dispersion and differential refractometry are used to measure mutual diffusion coefficients (D) for binary aqueous solutions of octylglucopyranoside, dodecylsulfobetaine, and sodium dodecyl sulfate (nonionic, zwitterionic and ionic surfactants, respectively). Aggregation causes a sharp drop in D as the concentration of each surfactant is raised through the critical micelle concentration (cmc). Differential mutual diffusion coefficients are determined in this composition region by using small initial concentration differences (3 mmol-dm^–3) and by extrapolating the measured D values to zero initial concentration difference relative to the carrier stream. The drop in D for each surfactant is more gradual than the concentration dependence predicted by the chemical equilibrium model of surfactant diffusion. Micelle polydispersity and nonideal solution behavior are discussed as possible explanations for this discrepancy. Intradiffusion coefficients (D*) for aqueous octylglucopyranoside and dodecylsulfobetaine are evaluated by integrating the relation d(cD*) = Ddc previously derived for dilute solutions of self-associating nonelectrolyte solutes.     

Quinary Mutual Diffusion Coefficients of Aqueous Mannitol + Glycine + Urea + KCl and Aqueous Tetrabutylammonium Chloride + LiCl + KCl + HCl Solutions Measured by Taylor Dispersion

Taylor dispersion is widely used to measure binary mutual diffusion. Studies of three- and four-component solutions show that the dispersion method is also well suited for multicomponent diffusion measurements, including cross-coefficients for coupled diffusion. Numerical procedures are reported here to calculate mutual diffusion coefficients from dispersion profiles measured for solutions of any number of components. The proposed analysis is used to measure the sixteen quinary mutual diffusion coefficients of five-component aqueous mannitol + glycine + urea + KCl solutions and aqueous NBu₄Cl + LiCl + KCl + HCl solutions. Mannitol, glycine, urea and KCl interact weakly at the low solute concentrations used (0.010 mol·dm^?3). The diffusion coefficients of this system are compared with pseudo-binary predictions. Strong coupling of the NBu₄Cl, LiCl, KCl and HCl fluxes is interpreted by using ionic conductivities and Nernst equations to calculate limiting quinary diffusion coefficients for mixed electrolytes that interact by the electric field generated by ion concentration gradients.     

Mutual diffusion coefficients of aqueous MnCl2 and CdCl2, and osmotic coefficients of aqueous CdCl2 at 25°C

Volume-fixed mutual diffusion coefficients have been measured for aqueous MnCl₂ and CdCl₂ solutions from 0.004 to 4.93–5.00 mol-dm^–3 (M) at 25°C. Diffusion coefficients for MnCl₂ decrease to a minimum, rise to a maximum, and then decrease rapidly; such behavior is typical for strong electrolytes. In contrast CdCl₂ diffusion coefficients decrease continuously with concentration; similar behavior is known for certain other associated electrolytes. Since thermodynamic diffusion coefficients for both salts are qualitatively similar, diffusion differences may be primarily due to thermodynamic rather than mobility factors. Isopiestic data were measured for CdCl₂ from 1.79 to 7.29 mol- (kg H₂O)^–1, and critically compared to other isopiestic and emf data for CdCl₂. Higher quality emf data are completely consistent with isopiestic data. Recommended smoothed values of activity coefficients, osmotic coefficients, water activities, and activity derivatives are given for CdCl₂ at 25°C.Work performed under the auspices of the Office of Basic Energy Sciences (Geosciences) of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract number W-7405-ENG-48.     

Viscosity of aqueous NH4Cl and tracer diffusion coefficients of ions,water and non-electrolytes in aqueous NH4Cl,KI, and MgCl2 at 25°C

Viscosities for aqueous NH₄Cl and tracer diffusion coefficients for²²Na⁺,³⁶Cl^–, HTO, and CH₃OH, acetone and dimethylformamide (all¹⁴C-labelled) in NH₄Cl supporting electrolyte are reported for 25°, together with tracer diffusion coefficients for²²Na⁺,³⁶Cl^–, and¹⁴CH₃OH in 1M KI, and for¹⁴CH₃OH in 1M MgCl₂. The diffusion coefficient of HTO in NH₄Cl solutions is slightly larger, for most of the concentration range investigated (0.05 to 4.5 M), than the value for pure water and is almost unaffected by the supporting electrolyte up to about 4M. Similar behavior is shown by CH₃OH, acetone and dimethylformamide in NH₄Cl solutions. Onsager limiting law behavior is approached by Cl^– at NH₄Cl concentrations in the 0.05–0.1M region but at much lower concentrations by Na⁺.     

Salt effects on cloud points and viscosities of polymethacrylates with pendant oligo-oxyethylene chains

Comblike polymethacrylates with oligo-oxyethylene side chains were synthesized from the commercially available monomers CH₂ ? C (CH₃) COO (CH₂CH₂O)_nCH ₃, the average n being 4, 8, and 22. The three polymers exhibited lower critical solution temperatures in aqueous media. Cloud points were determined as a function of the nature and concentration of salt. For salts that destabilize the polymer solutions, the cloud points decrease linearly with salt concentration, the extent of the decrease being strongly anion dependent. Salt effects on the viscosity of the polymers were measured in water, methanol, and acetonitrile. In water the viscosity decreases on adding salt, but in methanol and acetonitrile the neutral polymers are converted to polycations as cations form stable adducts with the oligo-oxyethylene side chains. The increase in viscosity is both cation and anion dependent. The general behavior of the comblike polymers resembles that reported for aqueous or methanolic salt solutions of poly (ethylene oxide) and nonionic surfactants.     

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.     

Investigation on extremely dilute solution of PEO by PFG-NMR

The technique of pulsed-field gradient nuclear magnetic resonance (PFG-NMR) was applied to study the solution properties of a series of low molecular weight poly(ethylene oxide). The self-diffusion coefficients of solutions from semi-concentrated to extremely diluted were measured, leading to a critical concentration. When the concentration of solution is higher than the value of critical concentration, the diffusion coefficient of the solute decreases as the concentration increases and remains the same when the concentration is lower than it. This critical concentration agrees well with the definition of dynamic contact concentration (C _s) and confirms indirectly the Flory's scaling law between the molecular weight and D ₀. In addition, the influences of molecular weight and terminal groups on C _s were discussed. All the diffusion coefficients determined at extremely dilute condition were equivalent to the diffusion coefficients at infinite concentration (D ₀), from which the polymer coil size was estimated.     

Nonisothermal membrane phenomena across perfluorosulfonic acid-type membranes,Flemion S: part I. Thermoosmosis and transported entropy of water

Solvent transports across the perfluorosulfonic acid-type membrane Flemion S were measured for aqueous electrolyte solutions under a temperature difference and under an osmotic pressure difference. H⁺, Li⁺, Na⁺, K⁺, NH ₄ ⁺ , CH₃NH ₃ ⁺ , (CH₃)₂NH ₂ ⁺ , (CH₃)₃NH⁺, (CH₃)₄N⁺, (C₂H₅)₄N⁺, (n-C₃H₇)₄N⁺ and (n-C₄H₉)₄N⁺ were used as counterions. Water flux across the membrane in HCl solution is higher than that in the other electrolyte solutions because hydrogen ions can exchange with the hydrogen of the neighbor water molecules and contribute to the water transport across the membrane as a proton jump in conductivity. The direction of thermoosmosis across the membrane in HCl, NaCl, (CH₃)₄NCl and (C₂H₅)₄NCl solutions was from the cold side to the hot side and that in LiCl, KCl, NH₄Cl, CH₃NH₃Cl, (CH₃)₂NH₂Cl and (n-C₄H₉)₄NBr solutions was from the hot side to the cold side, although thermoosmosis across anion-exchange membranes always occurs toward the hot side.     

Ternary Solution Mutual Diffusion Coefficients and Densities of Aqueous Mixtures of Sucrose with NaCl and Sucrose with KCl at 25°C

Ternary solution isothermal mutual diffusion coefficients (interdiffusion coefficients) have been measured for aqueous mixtures of 0.250 mol-dm^–3 sucrose (component 1) with 0.5 and 1.0 mol-dm^–3 NaCl or with 0.5 and 1.0 mol-dm^–3 KCl (salt = component 2) at 25.00°C using Rayleigh interferometry with computerized data acquisition. Densities were also measured. The volume-fixed diffusion coefficients (D _ij)_V show the following characteristics. At all compositions (D ₂₁)_V is much larger than (D ₁₂)_V and (D ₂₁)_V is a fairly significant fraction (33 to 68%) of (D ₁₁)_V. In addition, (D ₁₂)_V is slightly larger for mixtures containing NaCl than for those containing KCl at the same concentration, whereas (D ₂₁)_V is significantly larger for mixtures containing KCl. Values of (D ₁₁)_V are slightly larger for solutions containing KCl than for solutions containing NaCl. The observed trends imply that (D ₂₁)_V will probably exceed (D ₁₁)_V in both mixtures if concentrations of NaCl or of KCl are increased much further while maintaining the sucrose concentration at 0.250 mol-dm^–3. Finally, the solvent-fixed cross-term diffusion coefficients (D ₁₂)₀ and (D ₂₁)₀ are significantly larger than their corresponding (D ₁₂)_V and D ₂₁)_V.     

Ternary mutual diffusion coefficients of KCl-LaCl3-water mixtures from taylor dispersion profiles

The Taylor dispersion (peak-broadening) method is used to measure ternary mutual diffusion coefficients at 25°C for fifteen different compositions of the system KCl–LaCl ₃ -water at ionic strengths from 0.02 to 0.24 mol-dm^–3. The diffusion coefficients are evaluated by least-squares analysis of the refractive index profiles across the dispersed solute peaks. Diffusing LaCl ₃ is found to cotransport significant amounts of KCl. Monte Carlo simulations are used to estimate the precision of ternary diffusion coefficients determined by the dispersion method. Tracer diffusion coefficients are also reported for La ³⁺ ions in aqueous KCl solutions and for K⁺ ions in aqueous LaCl ₃ solutions.     

Micellization of monomeric and dimeric (gemini) surfactants in polar nonaqueous-water-mixed solvents

Dimeric or gemini surfactants are novel surfactants that are finding a great deal of discussion in the academic and industrial arena. They consist of two hydrophobic chains and two polar head groups covalently linked by a spacer. Data on critical micelle concentration (cmc) and degree of counterion dissociation (α) are reported on bis-cationic C₁₆H₃₃N⁺(CH₃)₂–(CH₂)_s–N⁺(CH₃)₂C₁₆H₃₃, 2Br⁻, referred to as 16-s-16, for spacer lengths s=4, 5, 6 in aqueous and in polar nonaqueous (1-propanol, 2-methoxyethanol or methyl cellosolve, dimethyl sulfoxide, acetonitrile)-water-mixed solvents. The behavior is compared with conventional monomeric surfactant cetyltrimethylammonium bromide (CTAB). Thermodynamic parameters are obtained from the temperature dependence of the cmc values. It is observed that micellization tendency of the surfactants decreases in the presence of polar nonaqueous solvents. However, detailed studies with dimethylsulfoxide (DMSO) show that the geminis nearly outclass the micellization-arresting property of this solvent. Also, within geminis, higher spacer length is found suitable for showing micellization even with high DMSO content (50% v/v). The implications of these results of gemini micellization may be useful in micellar catalysis in polar nonaqueous solvents.     

胶束及反胶束微环境中的槲皮素金属配合物

无机金属元素可与中药活性有机化合物通过配位键结合形成配合物,进而影响药物的生理活性[1]。但配合物的形成往往改变了原有机成分的溶解性能(如水溶性或脂溶性),而表面活性胶束体系可使金属有机配合物的水溶性或脂溶性得到明显改善,从而提高药物的生物利用度和改善药物的吸收。然而,胶束体系中已有的研究多是针对单纯的有机化合物[2]或生物分子如蛋白质[3]等,而涉及金属配合物胶束溶液的则很少,尤其是反胶束微环境中的中药金属配合物。反胶束亦称W/O型微乳液,是双亲物质在非极性有机溶剂中自发形成的具有纳米尺寸的含有水核的微小胶团聚集…     

Soret Coefficients for Aqueous Polyethylene Glycol Solutions and Some Tests of the Segmental Model of Polymer Thermal Diffusion

A thermogravitational cell is used to measure Soret coefficients (s) for dilute binary aqueous solutions of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol (PEG) fractions with average molecular weights from 200 to 20,000 g-mol^–1. The cell design allows the top and bottom halves of the solution column to be withdrawn and injected into a high-precision HPLC differential refractometer detector for analysis. Previously reported mutual diffusion coefficients D and the measured Soret coefficients are used to calculate thermal diffusion coefficients D _T. s and D vary with the PEG molecular weight M as M ^+0.53 and M ^–0.52, respectively; hence, D _T = sD is essentially independent of M. The segmental model of polymer thermal diffusion predicts D _T = D_seg U _S/RT ², where D _seg is the segment diffusion coefficient, U _S the solvent activation energy for viscous flow, R the gas constant, and T the temperature. The predicted D _T values, although independent of M, are too large by a factor of five. Additional tests of the segmental model are provided using literature data for polystyrene + toluene, n-alkane + CCl₄, and n-alkane + CHCl₃ solutions. Agreement with experiment is not obtained. In particular, the measured D _T values for the alkane solutions are negative.     

Investigations on a detergent system with rodlike micelles

Conductivity, kinetic, static and dynamic light scattering, electric birefringence and rheological measurements were carried out on aqueous solutions of Tetradecylpyridinium-n-Heptanesulfonate (C₁₄PyC₇SO₃) up to high concentrations. In dilute solutions between the critical micelle concentration (cmc) and another characteristic concentration (c _t) spherical micelles were detected whose radii were independent of detergent concentration and equal to the length of a detergent molecule; the aggregation numbern of these micelles of about 100 monomers per micelle was also in agreement with the existence of normal spherical micelles of aC ₁₄-detergent.Above the concentrationc _t, the spherical micelles were found to grow to rodlike aggregates whose short axis was still independent of concentration and equal to the length of a monomer, while the lengthsL of the rods increased with increasing detergent concentration. When the lengthsL of the rods became comparable with the mean distancea between them, the starting interaction between the rods slowed down their growth. In this concentration range of overlapping rods, the data could be evaluated with a recently developed theory by Doi and Edwards for stiff rods. The rods reached finally a maximum length of about 500 å and decreased again in size upon further increase of concentration when the overlap ratioL/a reached a value of about 1,5.     

ESR Studies on the Micellization Behaviors of a Series of Novel Asymmetric Gemini Surfactants

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｒｅｃｅｎｔｙｅａｒｓ ,ｂｉｓ(ｑｕａｔｅｒｎａｒｙａｍｍｏｎｉｕｍ)ｓｕｒｆａｃ ｔａｎｔｓｏｒｇｅｍｉｎｉｓｕｒｆａｃｔａｎｔｓ ,ｉｎｗｈｉｃｈｔｗｏｃａｔｉｏｎｉｃｓｕｒｆａｃ ｔａｎｔｍｏｉｅｔｉｅｓａｒｅｃｏｎｎｅｃｔｅｄｗｉｔｈｔｈｅａｍｍｏｎｉｕｍｈｅａｄｇｒｏｕｐｂｙａｐｌｏｙｍｅｔｈｙｌｅｎｅｃｈａｉｎ ,ｎａｍｅｌｙ ,ａｓｐａｃｅｒｈａｖｅｂｅｃｏｍｅｏｆｉｎｔｅｒｅｓｔｄｕｅｔｏｔｈｅｉｒｅｘｃｅｐｔｉｏｎａｌｓｕｒｆａｃｅａｃｔｉｖｉｔｙａｎｄｒｅｍ…