Self-motion of a camphanic acid disk on water with different types of surfactants

Control of the self-motion of a camphanic acid disk on water was investigated upon the addition of different kinds of surfactants (Triton X-100 and Brij58 as neutral surfactants, cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, and sodium dodecyl sulfate (SDS) as an anionic surfactant) to the water phase. With an increase in the concentration of surfactant, continuous motion changed to no motion via intermittent motion (repetition between motion and rest), and the concentration regions of these motions were different among these surfactants. Although the concentration regions of these motions were determined by the surface tension for neutral surfactants, they were different than those for CTAB and SDS. These characteristics of self-motion are discussed in relation to the surface tension, depending on the concentration of individual surfactants, and the hydrophilic effect of the surfactants.     

Photo-sensitive self-motion of a BQ disk

The photo-sensitive self-motion of a benzoquinone (BQ) disk was investigated on a hydroquinone (HQ) aqueous solution. The mode-switching of self-motion, i.e., continuous → intermittent → no motion, was observed with an increase in the concentration of HQ. Upon irradiation with UV light (～254 nm), the critical concentrations of HQ that were associated with the three modes of motion shifted to lower values, and the average speed of motion decreased. We discuss the mechanism of the photo-sensitive self-motion in relation to the photochemical reaction from BQ to HQ and the driving force of the disk.     

Self-motion of a phenanthroline disk on divalent metal ion aqueous solutions coupled with complex formation

The self-motion of a 1,10-phenanthroline disk on divalent metal ion aqueous solutions was investigated as a simple autonomous motor coupled with complex formation. The characteristic features of motion (continuous and oscillatory motion) and their concentration regions differed among metal ions, and the frequency of oscillatory motion depended on the temperature of the aqueous solution. The nature of the characteristic motion is discussed in relation to the stability constant of complex formation between phenanthroline and a metal ion, and the difference in surface tension between phenanthroline and its metal complex as the driving force.     

Wettability of polymeric solids by ternary mixtures composed of hydrocarbon and fluorocarbon nonionic surfactants

Contact angle (θ) measurements on poly(tetrafluoroethylene) (PTFE) and polymethyl methacrylate (PMMA) surface were carried out for the systems containing ternary mixtures of surfactants composed of: p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycols), Triton X-100 (TX100), Triton X-165 (TX165) and Triton X-114 (TX114), and fluorocarbon surfactants, Zonyl FSN100 (FSN100) and Zonyl FSO100 (FSO100). The aqueous solutions of ternary surfactant mixtures were prepared by adding TX114, FSN100 or FSO100 to binary mixtures of TX100+TX165, where the synergistic effect in the reduction of the surface tension of water (γ(LV)) was determined. From the obtained contact angle values, the relationships between cosθ, the adhesion tension and surface tension of solutions, cosθ and the reciprocal of the surface tension were determined. On the basis of these relationships, the correlation between the critical surface tension of PTFE and PMMA wetting and the surface tension of these polymers as well as the work of adhesion of aqueous solutions of ternary surfactant mixtures to PTFE and PMMA surface were discussed. The critical surface tension of PTFE and PMMA wetting, γ(C), determined from the contact angle measurements of aqueous solutions of surfactants including FSN100 or FSO100 was also discussed in the light of the surface tension changes of PTFE and PMMA under the influence of film formation by fluorocarbon surfactants on the surface of these polymers. The γ(C) values of the studied polymeric solids were found to be different for the mixtures composed of hydrocarbon surfactants in comparison with those of hydrocarbon and fluorocarbon surfactants. In the solutions containing fluorocarbon surfactants, the γ(C) values were different taking into account the contact angle in the range of FSN100 and FSO100 concentration corresponding to their unsaturated monolayer at water-air interface or to that saturated.     

Mode change in the self-motion of a benzoquinone disk coupled with a NADPH system

The self-motion of a benzoquinone (BQ) disk on NADPH was investigated as the coupling of an autonomous motor and an enzyme reaction. In the absence of the enzyme reaction, features of motion changed depending on the concentration of NADPH, that is, continuous motion→ intermittent oscillatory motion→ no motion. When the reverse reaction from NADP(+) to NADPH was introduced into the system with the addition of an enzyme reaction, continuous motion changed to intermittent oscillatory motion with small amplitude. The mechanism of this mode change is discussed in relation to the surface tension as a driving force and the time course of UV spectra as a window to the progress of the reaction. Characteristic features of the mode change were qualitatively reproduced by a numerical calculation.     

A new method for the determination of the critical micelle concentration of Triton X-100 in the absence and presence of beta-cyclodextrin by resonance Rayleigh scattering technology

A new method for the determination of the critical micelle concentration (CMC) of Triton X-100 in aqueous solution and beta-cyclodextrin solution by resonance Rayleigh scattering (RRS) has been developed. The method is based on the measurement of the RRS intensity of different concentration of Triton X-100 in aqueous solution and beta-cyclodextrin solution (6.0 x 10(-4) mol l(-1)). When the RRS intensities were plotted against the concentration of Triton X-100, an inflection point appeared at the Triton X-100 concentration of 5.0 x 10(-4) mol l(-1) in aqueous solution and 1.1 x 10(-3) mol l(-1) in beta-cyclodextrin solution, respectively. These values of concentration corresponded to the CMC of Triton X-100 in aqueous solution and beta-cyclodextrin solution, which also agreed closely with the results reported by surface tension and UV-Vis absorption spectrophotometry. Therefore, the present RRS method is very convenient, rapid and accurate and can be used as a new technology for the determination of CMC values of surfactants without any probe. The relationship between the RRS intensity and the concentration, aggregate state and the aggregate molecular size of Triton X-100 has been primarily discussed.     

Triton X-100在乙二醇中的胶体性质

表面活性剂在非水溶剂中聚集态的研究所见的报导与水体系相比要少得多．然而近年来对非水体系的研究日益增多．这是因为表面活性剂在非水溶剂中的应用日趋增加，但与水体系相反，对非水体系的性质了解甚少．对表面活性剂非水体系的研究还有助于对其聚集体的共溶剂效应有更深的认识．TritonX－100（以下简写为TX－100）是典型的非离子表面活性剂，在工业上有着广泛的应用．乙二醇在多醇中与水的化学结构最相近问，然而它却是水结构的破坏剂，加入少量的乙二醇会使水的冰点急剧下降．乙二醇又是蛋白质的变性溶剂．表面活性剂在乙二醇中的胶…     

Adsorption kinetics of octylphenyl ethers of poly(ethylene glycol)s on the solution—air interface

We studied the dynamic surface tension of aqueous solutions of Triton X-100 and Triton X-405 by the maximum bubble pressure and the inclined plate methods in the lifetime range from 0.001 s up to 10 s. It is established that in the region of large and ultimately small surface pressure and time the adsorption follows diffusion kinetics, but in the region of intermediate values of lifetime and surface pressure both the surfactants decrease the surface tension faster than predicted by the existing diffusion theory. We offer a model that provides for the ability of poly(ethylene glycol) chains to adsorb on the water-air interface and to change the area that a molecule occupies on the surface. For this model we achieve full coincidence of the measured values and the values calculated according to the diffusion theory of the dynamic surface tension.

It is ascertained that the Triton X-405 molecule can exist in the surface layer in different states: with the poly(ethylene glycol) chain fully expanded or with it partially or fully submerged in solution. The first state is most probable at surface pressures less than 5 mN m⁻¹, and the second is probable at a pressure of about 8–10 mN m⁻¹. At pressures larger than 15–20 mN m⁻¹, the poly(ethylene glycol) chain is fully submerged in the solution. The Triton X-100 molecule can also expand its poly(ethylene glycol) chain at low pressures and fully submerges it in the solution at higher values of the surface pressure.     

Surface Property of Nonionic Surfactant Triton X-100 in an Ionic Liquid

A common nonionic surfactant Triton X-100 was dissolved in a commercial ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF₄). The surface tension of the bmimBF₄ solution was decreased with increasing the content of surfactant Triton X-100, a similar phenomenon with aqueous solution systems. Dynamic surface properties of Triton X-100 in bmimBF₄ were measured. It was found that pure IL solvents need rearrangement at the air-bmimBF₄ interface during the beginning stage of absorption. Moreover, the adsorption model was found to be in accord with the diffusion-controlled adsorption mechanism, and further, the dilute bmimBF₄ solutions are close to the diffusion-controlled adsorption.     

Adsorption Kinetics of Some Polyethylene Glycol Octylphenyl Ethers Studied by the Fast Formed Drop Technique

The adsorption kinetics of Triton X-100 and Triton X-405 at solution/air and solution/hexane interfaces is studied by the recently developed fast formed drop technique. The dynamic interfacial tension of Triton X-100 and Triton X-405 solutions against hexane has been measured without preequilibration of the water and oil phases. It is found that the dynamic interfacial tension of Triton X-100 solutions passes through a minimum. This strange behavior is attributed to partial solubility of the surfactant in hexane. Such minima of the dynamic interfacial tension of Triton X-405 solutions have not been observed, which correlates well with the solubilities of both surfactants in hexane reported in the literature. The dynamic surface tension of solutions of both surfactants and the dynamic interfacial tension of Triton X-405 solutions are interpreted by the Ward and Tordai model for diffusion controlled adsorption. It is shown that proper interpretation of the experimental data depends on the type of isotherm used. More consistent results are obtained when the Temkin isotherm is used instead of the Langmuir isotherm. The results obtained with Triton X-100 at the solution/air interface confirm that the adsorption of this surfactant occurs under diffusion control. The adsorption of Triton X-405 at solution/air and at solution/hexane interfaces seems to occur under diffusion control at short periods of time, but under mixed (diffusion-kinetic) control at long periods of time. A hypothesis is drawn to explain this phenomenon by changes in the shape of the large hydrophilic heads of Triton X-405 molecules. Copyright 2000 Academic Press.     

聚醚型非离子型表面活性剂的混合表面膜I:Triton X-100,Triton X-305与硬脂酸、十六醇、聚丙二醇的二元混合膜

非离子型表面活性剂在乳化、起泡、分散、润湿、洗涤、润滑、防锈、抑制水蒸发等许多重要过程中有着广泛的应用.这些应用的关键往往在于界面膜性质的有效控制.关于非离子型表面活性剂的表面膜虽有过一些研究,但很少注意混合膜的,而实践中涉及的界面膜一般都是混合型的.本文报道Triton X-100. Triton X-305与硬脂酸. 十六醇. 聚丙二醇所组成的二元混合物在水面上的单分子膜,并对结果作了初步解释.     

Thermodynamic studies of mixed ionic/nonionic surfactant systems

Mixtures of alkyltrimethylammonium bromide (CnTAB, n=12, 14, 16, 18) and Triton X-100 were studied at a range of mole fractions of ionic surfactant per nonionic surfactant. For each mixture, the cmc obtained from surface tension measurements differed from that obtained using potentiometry. The behavior of these mixed-surfactant systems showed three different regions with increasing total surfactant concentration. From the surface tension and potentiometry data, we obtained the free monomer concentration of ionic surfactant (mi), the micellar mole fraction of surfactant (xi), and the degree of dissociation (alpha) of ionic surfactant. We also obtained the free monomer concentration of Triton X-100 (m2) using PFG-NMR technique. A new equation was introduced to evaluate the activity coefficient in the micellar phase. The excess free energy (GE) and the synergetic parameters of mixtures were determined at various mole fractions of CnTAB/Triton X-100. Finally, the complexity of the synergism parameters was investigated.     

Effect of surface composition on the adsorption of photosystem I onto alkanethiolate self-assembled monolayers on gold

We have used self-assembled monolayers (SAMs) prepared from omega-terminated alkanethiols on gold to generate model surfaces and examine the effect of surface composition on the adsorption of Photosystem I (PSI), stabilized in aqueous solution by Triton X-100. Triton-stabilized PSI adsorbs to high-energy surfaces prepared from HO- and HO2C-terminated alkanethiols but does not adsorb to low-energy surfaces. The inhibition of PSI adsorption at low-energy surfaces is consistent with the presence of a layer of Triton X-100 that adsorbs atop the hydrophobic SAM and presents a protein-resistant poly(ethylene glycol) (PEG) surface. While the presence of the PEG surface prevents the adsorption of PSI, the displacement of the inhibiting layer of Triton X-100 by dodecanol, a more active surfactant, greatly enhances the adsorption of PSI. This inhibiting effect by Triton X-100 can be extended to other protein systems such as bovine serum albumin.     

Dynamic Interfacial Tension of Surfactant Mixtures at Liquid-Liquid Interfaces

Dynamic interfacial tensions for surfactant mixtures at liquid-liquid interfaces were obtained with a drop volume tensiometer. The surfactants tested were Triton X-100, palmitic acid, and Span 80 at both the water-hexadecane and water-mineral oil interfaces. Two-surfactant mixtures were examined with the surfactants initially dissolved in different phases to minimize bulk-phase interactions. For concentrations below the CMC, it was found that the adsorption kinetics of palmitic acid and Triton X-100 mixtures were dominated by the latter surfactant. Apparent diffusion coefficients were obtained for Triton X-100 both in the absence and in the presence of palmitic acid. These values were largely insensitive to the presence of palmitic acid. For mixtures of Span 80 and Triton X-100, the adsorption kinetics were found to be influenced significantly by both surfactants. In this case, relative changes in surfactant concentrations affected the dynamic interfacial tension of the mixed system. A previously proposed multicomponent adsorption model described the dynamic interfacial tension adequately at low concentrations of Triton X-100, when desorption could be neglected. At higher concentrations, modifications were needed to account for solubilization into the oil phase. These corrections allowed the model to describe the long time adsorption quite well. However, predicted values of short time interfacial tensions were overestimated, likely due to a synergistic interaction of the two surfactants. Copyright 1999 Academic Press.     

Transfer of coenzyme Q0 from water to aqueous surfactant solutions: the case of Triton X-100

The effect of UQ0 on the micellization equilibrium of Triton X-100 has been studied by the analysis of the UV absorption spectra of Triton X-100. In the range of the UQ0 concentration investigated, the critical micelle concentration (CMC) increases at increasing of the solute concentration. The dependence of the CMC on UQ0 concentration has been used to calculate the generalized Setchenov constant. Mixing and dilution enthalpies of aqueous solutions of UQ0 and Triton X-100 were measured and used to calculate the enthalpies of transfer of UQ0 from water to Triton X-100 aqueous solutions. From the dependence of the enthalpy of transfer on surfactant concentration, the distribution constant between aqueous and micellar phase and the standard enthalpy of transfer from water to Triton X-100 micelles were evaluated along with the standard transfer free energy and entropy. All measurements were carried out at 298 K.     

Wettability of a polytetrafluoroethylene surface by an aqueous solution of two nonionic surfactant mixtures

Measurements of the advancing contact angle (theta) were carried out for an aqueous solution of p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycol)s (Triton X-100 (TX100) and Triton X-165 (TX165) mixtures) on polytetrafluoroethylene (PTFE). The obtained results indicate that the wettability of PTFE depends on the concentration and composition of the surfactant mixture. The minimum of the dependence between the contact angle and composition of the mixtures for PTFE for each concentration at a monomer mole fraction of TX100, alpha = 0.8, points to synergism in the wettability of PTFE. This effect was confirmed by the negative values of interaction parameters calculated on the basis of the contact angle and by the Rosen approach. In contrast to Zisman, there was no linear dependence between cos theta and the surface tension of an aqueous solution of TX100 and TX165 mixtures for all studied systems, but a linear dependence existed between the adhesional tension and surface tension for PTFE over the whole concentration range, the slope of which was -1, indicating that the surface excess of the surfactant concentration at the PTFE-solution interface was the same as that at the solution-air interface for a given bulk concentration. Similar values of monomer mole fractions of the surfactants at water-air and PTFE-water interfaces calculated on the basis of the surface tension and contact angles showed that adsorption at these two interfaces was the same. It was also found that the work of adhesion of an aqueous solution of surfactants to the PTFE surface did not depend on the type of surfactant and its concentration. This means that for the studied systems the interaction across the PTFE-solution interface was constant and was largely of Lifshitz-van der Waals type. On the basis of the surface tension of PTFE, the Young equation, and the thermodynamic analysis of the adhesion work of an aqueous solution of surfactant to the polymer surface, it was found that in the case of PTFE the changes in the contact angle as a function of the mixture concentration of two nonionic surfactants resulted only from changes in the polar component of the solution surface tension.     

Composition of Surface Layer at the Water–Air Interface and Micelles of Triton X-100 + Rhamnolipid Mixtures

Measurements of the surface tensions, densities and viscosities of aqueous solutions of Triton X-100 (TX-100) and rhamnolipid (RL) mixtures, at constant concentration of RL or TX-100, were carried out. The measured values of the surface tension were compared to those determined using different theoretical models and on the basis of the surface tension of aqueous solutions of individual surfactants. From the surface tension isotherms, the Gibbs surface excess concentration of TX-100 and RL, the composition of surface layer and the standard Gibbs free energy of adsorption at the water–air interface were determined. Moreover, on the basis of surface tension, density and viscosity isotherms, the CMC of surfactants mixtures were evaluated. From the density isotherms, apparent and partial molar volumes of TX-100 and RL were also determined. These volumes were compared to those calculated from the sizes of TX-100 and RL molecules. There was observed a synergetic effect in the reduction of water surface tension and micelle formation, which was confirmed by the intermolecular interactions parameter. In the case of micelle formation, this effect was discussed based on the standard Gibbs free energy of micellization as well as of TX-100 and RL mixing in the micelles. The synergism of TX-100 and RL mixtures in the reduction of water surface tension and micelle formation was explained on the basis of electrostatic interactions between the hydrophilic part of TX-100 and RL molecules; this was supported by pH measurements.     

Self-Assembled Supramolecular Micellar Structures Based on Non-ionic Surfactants and Cyclodextrins

The complexation between non-ionic polyethylene oxide (PEO)-based surfactants (Triton X-45, Triton X-100, polyethylene glycol-1000-monostearate, and Brij 35) and cyclodextrins is studied. It is shown that the addition of surfactant solutions to the aqueous solution of alpha, beta-, and gamma-cyclodextrins affords poorly soluble crystalline precipitates. Parameters of crystalline structure and the composition of complexes are analogues to those obtained on the basis of polyethylene oxide. Using a method of surface tension it is shown that cyclodextrins favor the increase of the value of critical micelle concentration (CMC) of surfactants. The dependence of CMC from the molar ratio cyclodextrin/surfactant permits us to determine the composition of inclusion complexes in solution. For Triton X-100 and polyethylene glycol-1000-monostearate values of stoichiometric composition of complexes in solution and in condensed phase agree well. It is shown that in the presence of beta-cyclodextrin the destruction of micelles based on Triton X-100 occurs. UV-spectroscopy is used for the investigation of the microenvironment of a phenyl group in inclusion complexes based on alpha- and beta-cyclodextrins. The interaction of gamma-cyclodextrin with PEO surfactants results in the formation of novel double-tailed surfactants. The values of CMC registered in solutions of these complexes is lower than the corresponding value of Triton X-100 and polyethylene glycol-1000-monostearate. The stoichiometric composition of complexes in solution is established from the dependence of CMC versus the gamma-cyclodextrin/surfactant ratio. The composition of the complexes in solution and condensed phase agree well. The interaction of alpha- and gamma-cyclodextrins with Brij 35 results in the formation of nonstoichiometric complexes. The investigation of the dependences of CMC of modified surfactants from temperature shows that these supramolecular structures exist at high temperatures. Copyright 1999 Academic Press.     

The Micellization and Clouding Phenomena of a Nonionic Surfactant,Poly(ethylene glycol) t-octylphenyl ether (Triton X-100): Effect of (Chloride Salt) Electrolytes

Herein, we report the micellization and the clouding of a nonionic surfactant, poly(ethylene glycol) t-octylphenyl ether (Triton X-100), in aqueous solutions in the absence and presence of (chloride salt) electrolytes. In the absence and presence of electrolytes, the critical micelle concentration (CMC) of Triton X-100 was measured by surface tension measurements. Upon increasing the temperature as well as the concentration of electrolytes, the CMCs decreased. The surface properties and the thermodynamic parameters of the micellar systems were evaluated. From these evaluated thermodynamic parameters, it was found that in the presence of an electrolyte, the stability of the micellar system is high. The cloud points (CPs) of Triton X-100 were also measured in the absence and presence of metallic ions of electrolytes. Upon the addition of metallic ions of chloride salts (electrolytes), the decrease in CP values was observed and the order was found to be: K⁺ > Na⁺ > Li⁺ > NH⁺₄.     

Effect of nonionic surfactant on wetting behavior of an evaporating drop under a reduced pressure environment

The evaporation of sessile drops at reduced pressure is investigated. The evaporation of water droplets on aluminum and PTFE surfaces at reduced pressure was compared. It was found that water droplets on an aluminum surface exhibit a 'depinning jump' at subatmospheric pressures. This is when a pinned droplet suddenly depins, with an increase in contact angle and a simultaneous decrease in the base width. The evaporation of sessile water droplets with a nonionic surfactant (Triton X-100) added to an aluminum surface was then studied. The initial contact angle exhibited a minimum at 0.001 wt% Triton X-100. A maximum in the evaporation rate was also observed at the same concentration. Droplets with low surfactant concentrations are found to exhibit the 'depinning jump.' It is thought that the local concentration of the surfactant causes a gradient of surface tension. The balance at the contact angle is dictated by complex phenomena, including surfactant diffusion and adsorption processes at interfaces. Due to the strong evaporation near the triple line, an accumulation of the surfactant will lead to a surface tension gradient along the interface. The gradient of surface tension will influence the wetting behavior (Marangoni effect). At low surfactant concentrations the contact line depins under the strong effect of surface tension gradient that develops spontaneously over the droplet interface due to surfactant accumulation near the triple line. The maximum evaporation rate corresponds to a minimum contact angle for a pinned droplet.