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1.
The behavior of an ionic liquid (IL) within aqueous micellar solutions is governed by its unique property to act as both an electrolyte and a cosolvent. The influence of the surfactant structure on the properties of aqueous micellar solutions of zwitterionic SB‐12, nonionic Brij‐35 and TX‐100, and anionic sodium dodecyl sulfate (SDS) in the presence of the “hydrophobic” IL 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF6]) is assessed along with the possibility of forming oil‐in‐water microemulsions in which the IL acts as the “oil” phase. The solubility of [bmim][PF6] within aqueous micellar solutions increases with increasing surfactant concentration. In contrast to anionic SDS, the zwitterionic and nonionic surfactant solutions solubilize more [bmim][PF6] at higher concentrations and the average aggregate size remains almost unchanged. The formation of IL‐in‐water microemulsions when the concentration of [bmim][PF6] is above its aqueous solubility is suggested for nonionic Brij‐35 and TX‐100 aqueous surfactant solutions. 相似文献
2.
Schrade P Klein H Egry Ademovic Z Klee D 《Journal of colloid and interface science》2001,234(2):445-447
Density measurements of aqueous albumin solutions as a function of concentration and temperature are reported. The solvents were H(2)O, D(2)O, and a physiological H(2)O-based buffer. An anomaly of the density at very small concentrations of albumin in D(2)O was found. Furthermore, the partial specific volume of albumin is remarkably different in D(2)O and H(2)O. We attribute both effects to structural differences of the solvents. Copyright 2001 Academic Press. 相似文献
3.
A. S. Komolov A. B. Mel'nikov K. Schaumburg E. I. Ryumtsev A. V. Lezov 《Colloid Journal》2002,64(2):155-159
The conformations of the molecules of DNA–surfactant complexes in dilute solutions and on the atomic smooth surfaces of mica and highly oriented pyrolytic graphite were comparatively studied by the methods of isothermal diffusion, electric birefringence, and atomic force microscopy. The DNA–surfactant complexes were deposited onto the substrates from a chloroform solution. The number of particles of the DNA–surfactant complex on the substrate was changed by varying the concentration of the initial solution within three orders of magnitude. The particles of a shape close to ellipsoidal, 25–70 nm in diameter and 2–4 nm high, were observed at the lowest concentration of DNA–surfactant solution on the mica substrate. The shape and size of these particles correspond to those of a single DNA–surfactant complex, calculated from its translational diffusion coefficient and the time of orientational relaxation in dilute solutions. An increase in the number of molecules deposited onto the substrate leads to an increase in the characteristic sizes of DNA–surfactant complex particles observed by the atomic force microscopy. This may be associated with the aggregation of DNA–surfactant complexes. 相似文献
4.
This paper presents the results of numerical simulations of the unsteady motion of a single bubble that is released or injected into water. The governing equations are solved with a finite difference method using an adaptive boundary-fitted coordinate system. Results are shown for bubbles in the size range 0.72 to 1.5 mm. The effects of surfactants on the motion and shape of the bubble are investigated. When the surfactant concentration is sufficiently small, the bubble attains a maximum velocity before slowing down to its steady-state velocity. Although the steady-state velocity is nearly independent of surfactant concentration, the maximum velocity can be comparable to steady-state velocity in pure water. This behavior is observed even when the bubble is allowed to equilibrate prior to releasing it. The formation of an immobilized surfactant cap is observed soon after the bubble is released. The effect of the injection velocity on the bubble velocity profile is investigated. The effects of the sorption rate constants and the bulk surfactant concentration on the behavior of the bubble are investigated. The feasibility of using experimental measurements and simulations of unsteady bubble velocities to estimate sorption rate constants is discussed. Copyright 2000 Academic Press. 相似文献
5.
Active carbon, used in various types of chemical protection devices, can absorb an extremely wide range of hazardous compounds. Unfortunately, this universal absorption includes ubiquitous water molecules, which can result in saturation and premature loss of efficacy. The purpose of this work has been to treat active carbon-impregnated fabric with appropriate low-pressure plasmas, so as to render the carbon surface hydrophobic, while minimally affecting its ability to absorb toxic gases or vapors (simultated here by CCl4). The best results have been achieved using plasma polymerization of organosilicon (PP-HMDSO) thin films onto the fabric surface: This has been done in a pilot-scale microwave plasma reactor system, designed for treating continuously-moving flexible web materials up to 30 cm in width. Under optimal treatment conditions, a plasma exposure duration of 10 s (PP-HMDSO film thickness, d 40 nm) is found to be sufficient to reduce water absorption by 85%, while the corresponding reduction in CCl4absorption is small (<20%). The treatment demonstrates long-term stability, and it holds promise for commercial implementation on existing roll coaters. 相似文献
6.
Surfactants are widely spread in nature and are increasingly used in industry as wetting, cleaning and disinfecting agents. Recently, there are newly discovered trisiloxanes and other silicone based surfactants which show very unusual spreading behaviour. Although a number of experimental and theoretical investigations have been carried out, the underlying spreading mechanism remains unclear. Experiments using trisiloxanes and comparison with 3 different poly(ethylene glycol) monododecyl ethers (C12E4, C12E5, and C12E6) surfactants were performed to understand the influence of Marangoni force as the driving force for the spreading. We then compared our experimental results to available theoretical predictions in the literature. The obtained experimental data showed the opposite trend as compared with the theoretical predictions developed for regular surfactants. The latter is assumed to be a special feature of “superspreaders”. The article is published in the original. 相似文献
7.
8.
Masrat Maswal Altaf Hussain Pandith Nasrul Islam Aijaz Ahmad Dar 《Journal of solution chemistry》2013,42(7):1374-1392
Co-solubilization of the hydrophobic drugs Carbamezipine (CBZ) and Nifedipine (NFD) by micellar solutions at 25 °C, using two series of polyoxyethylene based nonionic surfactants, was measured and compared. The first series is composed of surfactants with a 12 carbon (C12) hydrophobic chain while the second series had 16 carbon (C16) hydrophobic chains. Experimental results were obtained for solubilization and co-solubilization of CBZ and NFD within the micelles at saturation and quantification was done in terms of the molar solubilization ratio and the micelle–water partition coefficient employing spectrophotometric and tensiometric techniques. The extent of micellar solubilization of CBZ is much greater than NFD. The C12 series of surfactants exhibit higher solubilization capacities for CBZ than the C16 series while the reverse is the case for NFD. Co-solubilization results showed competitive solubilization of the drugs. A synergistic effect on the solubilization of NFD was observed in the presence of CBZ in Brij30 and Brij56 surfactant systems while, in the remaining surfactants, the solubility of NFD was slightly reduced. Since the surfactants used in the present study are either nontoxic or have minimal toxicity, it is expected that they can be employed as drug delivery vehicles for co-administration of the two drugs in vivo. Both from industrial and research points of view, this paper reports a comprehensive study for co-solubilization of differently structured drugs in micellar media. 相似文献
9.
Ghannam MT 《Journal of colloid and interface science》2003,262(2):435-441
Wetting characteristics of crude oil droplets over limestone substrates in the presence of different aqueous solutions are investigated in terms of wetting length, droplet depth, contact angle, and spreading coefficient. A wide range of concentration of NaOH, Alcoflood polymer, and nonionic Triton X-100 surfactant are used as a continuous phase for the crude oil droplet. NaOH and Triton X-100 significantly enhanced the spreading characteristics of the crude oil droplet; however, AF1235 polymer caused a huge reduction in the spreading behavior of crude oil. 相似文献
10.
Starov VM Kosvintsev SR Sobolev VD Velarde MG Zhdanov SA 《Journal of colloid and interface science》2002,246(2):372-379
Spreading of small liquid drops over thin porous layers saturated with the same liquid is investigated from both theoretical and experimental points of view. A theory is presented that shows that spreading is governed by the same power law as in the case of spreading over a dry solid substrate. The Brinkman's equations are used to model the liquid flow inside the porous substrate. An equation of the drop spreading is deduced, which shows that both an effective lubrication and the liquid exchange between the drop and the porous substrates are equally important. The presence of these two phenomena removes the well-known singularity at the moving three-phase contact line. Matching of the drop profile in the vicinity of the three-phase contact line with the main spherical part of the drop gives the possibility to calculate the pre-exponential factor in the spreading law via permeability and effective viscosity of the liquid in the porous layer. Unfortunately, the latter dependency turns out to be very weak. Spreading of silicone oils over different microfiltration membranes is carried out. Radii of spreading on time experimental dependencies confirm the theory predictions. Experimentally found coefficients agree with theoretical estimations. 相似文献
11.
The zwitterionic micelles formed with two carboxybetaines and fivesulfobetaines have been investigated by micellar catalysis and dye solubility studieswith the probe Ni2+/PADA complexation reaction and the dye,pyridine-2-azo-p-dimethylaniline (PADA). Catalysis occurs with the carboxybetaines, butinhibition of the probe reaction arises with all of the sulfobetaines. Bothreactants enter carboxybetaine micelles, but Ni2+ ions are not appreciablyadsorbed by sulfobetaine micelles. 相似文献
12.
The kinetics of dewetting (a decrease in contact angles and wetted surface area) during the evaporation of drops of cetyltrimethylammonium bromide (CTAB) solutions from paraffin and Teflon surfaces was studied in a wide concentration range. Three different stages of this process were found: (1) a monotonic decrease in the contact angle at a fixed position of the three-phase contact line, (2) contraction of the wetted surface area (the drop base) at a constant contact angle, and (3) simultaneous contraction of the drop base and a decrease in the contact angle. The CTAB distribution over a solid surface after the drop evaporation was studied by autoradiography. Depending on the surfactant concentration and the nature of a hydrophobic substrate, dewetting occurs by two mechanisms: slipping and carpet rolling. 相似文献
13.
Spreading of aqueous drops on hydrocarbon liquids occurs only when particular surfactants are added to the droplets above a critical concentration. For surfactant solutions of didodecyl ammonium bromide (DDAB) in water spreading over mineral oil, rates of droplet expansion are much slower than those corresponding to pure liquids spreading over immiscible liquid substrates with the same initial spreading coefficients. We present a sorption-kinetic model to explain quantitatively the spreading histories for aqueous DDAB droplets on mineral oil. Due to surfactant transport limitations, spreading occurs only when enough surfactant arrives at the dilating lens surfaces to establish a slightly positive, but near-zero spreading coefficient. We solve the convective diffusion equation for a cylindrical disk-like lens under the integral constraint of a constant surfactant adsorption density corresponding to a near-zero spreading coefficient. All observed spreading behavior is correctly portrayed by the proposed sorption-kinetic model including final equilibrium lens formation and spreading rates that are sensibly independent of drop volume, but are strongly dependent on drop surfactant concentration. Quantitative agreement is found with the experimental spreading data for a surfactant diffusion coefficient of 6x10(-12) m(2)/s and an effective adsorption rate constant of 6.5x10(-7) m/s. Both values prove physically reasonable. The sorption-kinetic model provides a new mechanism for understanding slow surfactant-driven spreading. Copyright 2000 Academic Press. 相似文献
14.
Theoretical results published in the last 17 years on the kinetics of aggregation and relaxation in micellar surfactant solutions have been reviewed. The results obtained by the analytical and direct numerical solution of the Becker–Döring kinetic equations and the Smoluchowski generalized equations, which describe different possible mechanisms of aggregation and relaxation on all time scales from ultrafast relaxation while reaching the quasi-equilibrium in the region of subcritical molecular aggregates to the last stage of slow relaxation of micelles to the final aggregated state, have been considered in detail. The droplet model and the model linear with respect to aggregation numbers have been used for the work of aggregation to describe the dynamics of the rearrangement of micellar systems consisting of only spherical, only cylindrical, and coexisting spherical and cylindrical aggregates, with the dynamics being both linear and nonlinear with respect to deviations from equilibrium. The results of molecular simulation of the rearrangement kinetics of micellar systems subjected to initial disturbance have been reviewed. 相似文献
15.
The Becker–Döring kinetic equations are employed to describe the stage of ultrafast relaxation in micellar surfactant solutions, which ends in the establishment of a quasi-equilibrium distribution in the premicellar region of aggregate sizes. This is performed by analyzing the spectrum of the eigenvalues of the matrix of kinetic coefficients of the linearized Becker–Döring difference equations, which describes the complete multistage relaxation in a micellar system. The first value of the spectrum ordered as an ascending series is equal to zero (infinite relaxation time), thereby corresponding to the law of conservation of the surfactant quantity. The second value is very small; it differs from the series of subsequent values by several orders of magnitude and determines the time of slow relaxation. The other eigenvalues describe the processes of fast relaxation and comprise the contributions from the relaxation processes in both micellar and premicellar regions of aggregate sizes. In the latter region of the spectrum, the contribution of the ultrafast relaxation can be numerically distinguished. The obtained result is confirmed by the analysis of the spectrum of relaxation times of premicellar aggregates, which are considered as a closed system. It is also shown that the spectrum of ultrafast relaxation times is mainly determined by the first diagonal elements of the matrix of the linearized Becker–Döring equations and can be described analytically. 相似文献
16.
The reverse flow (i.e., the efflux from glass capillaries occurring after the stop of capillary rise) of mixed aqueous solutions of nonionic (Triton X-100) and cationic (cetyl- and dodecyltrimethylammonium bromides) surfactants is studied. The effect of electrolytes (salts and acids) on the process kinetics and the wetting in these systems is investigated. Possible causes of the reverse flow are discussed. They are related to the peculiar features of the interaction of nonionic and cationic surfactants with glass and to the differences in the surfactant adsorption from quiescent and moving solutions. It is shown that the wetting by the mixed surfactant solutions, including its kinetics, can be controlled by the addition of electrolytes. 相似文献
17.
Yan An GAO Zhong Ni WANG Jin ZHANG Wan Guo HOU Gan Zuo LI* Bu Xing HAN* Feng Feng Lü Gao Yong ZHANG Key Laboratory of Colloid Interface Chemistry 《中国化学快报》2005,16(7):963-966
The surfactant TX-100 can be dissolved in ionic liquid bmimPF6 and decrease the surface tension of 1-buty1-3-methylimidazolium hexafluorophosphate (bmimPF6) solutions. Here, we confirmed that in this new system, the pure solvents need rearrangement at the air-wate rinterface at the initial stage. The dynamic surface tension (DST) study shows that at the initial adsorption stage, the adsorption model of surfactant accords with the diffusion-controlled adsorption mechanism, and the dilute ionic liquids solutions is further close to the diffusion-controlled adsorption. 相似文献
18.
Jennifer A. MacNeil Gargi B. Ray Poonam Sharma Derek G. Leaist 《Journal of solution chemistry》2014,43(1):93-108
Osmotic techniques for measuring thermodynamic activities, such as isopiestic equilibration, are well established for multicomponent solutions, especially mixed salt solutions. Surprisingly, these techniques have not yet been applied to mixed ionic surfactants, despite the numerous practical applications of these systems and the importance of the Gibbs free energy for micelle stability. In this study, mass-action equations are developed for the osmotic coefficients of solutions of ionic surfactant CA + ionic surfactant CB, with common counterion C. Extended Debye–Hückel equations are used for the ionic activity coefficients. The equilibrium constants for mixed micelle formation are evaluated by Gibbs–Duhem integration of critical micelle concentrations. Fitting the derived equations to the osmotic coefficients of aqueous sodium decanoate + sodium dodecylsulfate solutions measured by freezing-point osmometry is used to evaluate the activities of the total surfactant components. Very large departures from ideal solution behavior are indicated, including stoichiometric surfactant activity coefficients and micelle activity coefficients that drop below 0.05 and 10?8, respectively, relative to unity for ideal solutions. Osmometry offers many interesting and unexplored possibilities for studies of mixed surfactant thermodynamics. 相似文献
19.
Colloid Journal - The macroscopic theory of the van der Waals forces has been used to calculate disjoining pressure isotherms for silicone oil and perfluorodecalin films on silica substrates. Both... 相似文献
20.
Dianlong Zhang Wenshan Qu Cuiping Zhang 《Journal of Dispersion Science and Technology》2016,37(12):1778-1782
The dynamic surface activity in solutions and dynamic spreading on low-energy surfaces of isotridecanol ethoxylates with two different units were investigated by using the Wilhelmy plate, maximum bubble pressure, and contact angle method. The dynamic surface activity was analyzed by using the classical Rosen model, and the dynamic spreading was depicted by decay function. The equilibrium contact angle (θe value) and the spread rate (K value) were suggested to evaluate effectiveness and efficiency of spreading. 相似文献