ABSTRACT
Despite the fact that the wetting properties of multicomponent mixtures including the surface active compounds play a very important role in many practical applications, they are not sufficiently known. Thus, the wettability of polytetrafluoroethylene (PTFE) and poly (methyl methacrylate) (PMMA) by the water + ethanol (ET) solution of rhamnolipid (RL) with Triton X-165 (TX165) mixture was studied. The investigations involved measuring the advancing contact angles of this solution on PTFE and PMMA by varying the concentration of TX165 while maintaining a constant concentration of ET and RL. Additionally, a thermodynamic analysis was conducted to obtain the compositions and concentrations of the ET, RL, and TX165 mixtures at the different interfaces. The composition and concentration of the interface mixed layer were considered using two different approaches to the wetting process. From these considerations, it follows that, depending on the ET concentration, it is possible to form the TX165 + RL layer at the solid-water + ET mixed solvent, as well as the water + ET-air interfaces, but not at the solid-water and water-air ones. This conclusion is in accordance with the Gibbs standard free energy of adsorption of particular components of the studied mixture at the solution-air and solid-solution interfaces.
ABSTRACT
In many industrial fields, in medicine or pharmacy, there are used multi-component mixtures of surfactants as well as more and more often mixtures containing biosurfactants. Thus, in our study the mixtures of rhamnolipid (RL), ethanol (ET) and Triton X-165 (TX165) were applied. For these mixtures the surface tension of aqueous solutions with constant concentration and composition of ET and RL as well as the variable concentration of TX165 was measured. Based on the obtained results and the literature data, thermodynamic analyses of the adsorption process of ET, RL, TX165, binary mixtures of ET + RL, ET + TX165 and RL + TX165 as well as the ternary mixtures of RL + ET + TX165 at the water-air interface were made. This analysis allows to propose a new equation for calculation of the total ethanol concentration at the water-air interface using the Guggenheim-Adam adsorption isotherm. The constants in the Langmuir and Szyszkowski equations for each component of the studied mixtures as well as the composition of the mixed monolayer at the water-air interface were also successfully analysed based on the contribution of particular surface active compounds to the water surface tension reduction as well as based on the Frumkin isotherm of adsorption.
Subject(s)
Ethanol , Water , Surface-Active Agents , Surface Tension , Thermodynamics , AdsorptionABSTRACT
The aim of this research was to elucidate the surface active properties of Saponaria officinalis (soapwort) extract containing the plant surfactants saponins. To this end, the advancing contact angle (θ) of water, formamide and diiodomethane on the glass, as well as θ of the aqueous solution of S. officinalis extract fractions on PTFE, PMMA and glass, were studied. Based on the obtained results, the wetting behaviour of saponins was considered with regard to the surface tension components and parameters of the solutions and solids. The investigations also involved the description of the θ isotherms, the dependences between the cosine of contact angle and/or the adhesion of the solution to the solid surfaces and solution surface tension, as well as the critical surface tension of PTFE, PMMA and glass wetting. These dependences were studied based on the saponin adsorption at the different interfaces, which was deduced from the dependence between the adhesion and surface tension of the solution, as well as using the Gibbs and Frumkin isotherm equations. This proved that the saponins are poor wetting agents and that the contact angle isotherm can be described by the exponential function of the second order as well as the Szyszkowski equation, but only for PTFE.
Subject(s)
Polymethyl Methacrylate , Saponins , Surface Properties , Thermodynamics , Water , PolytetrafluoroethyleneABSTRACT
The poor solubility of berberine (Ber) in water limits its practical use. Its solubility can be increased, among other ways, by the addition of surfactants. Of the surfactants, Kolliphor® ELP (ELP) and Kolliphor® RH 40 (RH40) can be very useful in this respect. The increase of Ber's solubility in water in the presence of ELP and RH40 should be reflected in the composition of the surface layers at the water-air interface and the micelles. The determined composition is reflected in the Gibbs energy of interactions of berberine with ELP and RH40 through the water phase and the standard Gibbs free energy, enthalpy, and entropy of adsorption and micellization. These energies were determined from the equations proposed by us, based on the Gibbs surface excess concentration of the Ber mixture with ELP and RH40, the activity of these compounds in the surface layer at the water-air interface and in the micelles obtained by the Hua and Rosen method, and the contributions of Ber, ELP, and RH40 to the reduction in the water surface tension. For this determination, the measurements of the surface tension of the aqueous solution of the Ber mixture with ELP or RH40 and that of the Ber mixture with these two surfactants, as well as the density and conductivity were performed. Moreover, the fluorescence emission spectra for the Ber + surfactant mixtures were recorded.
ABSTRACT
The adsorption and volumetric properties of the Triton X-114 (TX114), Tween 80 (T80), quercetin (Q) and rutin (Ru) at the different temperatures in relation to above properties of the TX114 and T80 mixtures with quercetin and rutin in the absence and presence of alcohol were discussed based on the studies reported in the literature. The adsorption isotherms of the mixtures of the nonionic surfactants with flavonoids in the presence and absence of alcohol were analyzed based on the isotherms of the surface tension of the particular mixture components and thermodynamic parameters of the adsorption of these components at the water-air interface. The surface tension isotherms of the particular component of the mixtures were taken into account while considering the surface tension isotherms of the mixtures and the composition of the mixed surface layer at the water-air interface. Different ways of the mixed surface layer composition determination were shown. The values of the surface tension and composition of the mixed surface layers obtained using different methods were discussed in the light of the intermolecular interactions and their contribution to the surface tension of the surfactants mixture with flavonoids and alcohol. The composition of the mixed monolayer and the bulk phase were compared and the differences between them were explained. The behaviour of the nonionic surfactants and flavonoids in the presence and absence of alcohol was analyzed in relation to the micelle formations and molar volumes of the mixtures and their components. Moreover, the micelles composition and their size as well as the thermodynamic parameters of the micellization process were analyzed.
ABSTRACT
The studies on the behavior of Auramine O (AuO) at the water-air interface and in the bulk phase of the aqueous solution of Kolliphor® ELP (ELP) and Kolliphor® RH 40 (RH40) and their mixture were based on the results obtained from the measurements of the contact angle of water, formamide and diiodomethane on the polytetrafluoroethylene covered by the AuO layer, the surface tension of the aqueous solution of AuO, AuO + ELP, AuO + RH40, AuO + ELP + RH40, density and fluorescence intensity. Based on the obtained results, it was possible to determine components and parameters of the AuO surface tension, concentration and composition of the mixed monolayer, including AuO, ELP and RH40, as well as that of the mixed micelles, and to determine the Gibbs standard free energy of adsorption, micellization and AuO solubilization. The obtained results also showed that surface tension isotherms of the studied solutions can be described by the Szyszkowski equation and the exponential function of the second order and predicted by the Fainerman and Miller equation. In addition, the mixed surface layer composition can be predicted based on the contribution of the components of this layer to the water surface tension reduction.
Subject(s)
Benzophenoneidum , Water , Solutions , Surface Tension , MicellesABSTRACT
The wetting properties of the rhamnolipid and surfactin mixtures with Triton X-165 were considered based on the contact angle measurements of their aqueous solution on the polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA) and quartz (Q) surfaces. The obtained contact angle isotherms were described by the exponential function of the second order as well as by Szyszkowski equation in some cases. Using the contact angle isotherms of individual biosurfactants and TX165 as well as the earlier obtained isotherms of their surface tension the contact angle isotherms of the biosurfactants mixtures with TX165 were deduced. As follows the presence of the maxima on the contact angle isotherms of the biosurfactants mixtures with TX165 is justified. They do not prove negative adsorption of the biosurfactant and TX165 at the interfaces. However, the mutual exchange of the biosurfactant and TX165 molecules is observed in the layers at the interfaces. The concentration of the studied mixtures at the PTFE-solution interface was established to be close to that at the solution-air one but that at the PTFE-air is equal to zero. However, the concentration of the studied mixtures at the PMMA-solution and quartz-solution is greater than zero. The concentration at the PMMA(quartz)-air and PMMA(quartz)-solution interfaces is smaller than that at the solution-air one.
Subject(s)
Polymethyl Methacrylate , Quartz , Benzene Derivatives , Glycolipids , Polyethylene Glycols , Polytetrafluoroethylene , Surface-Active AgentsABSTRACT
The surface tension of aqueous solutions of Triton X-165 with rhamnolipid or surfactin mixtures was measured. The obtained results were applied for the determination of the concentration and composition of the Triton X-165 and biosurfactants mixture at the water-air interface as well as the contribution of the particular component of the mixtures to water surface tension reduction and the mutual influence of these components on the critical micelle concentration. The determination of these quantities was based on both the commonly used concepts and a new one proposed by us, which assumes that the composition of the mixed monolayer at the water-air interface depends directly on the pressure of the monolayer of the single mixture component and allows us to determine the surface concentration of each mixture component independently of surface tension isotherms shape. Taking into account the composition of the mixed monolayer at the water-air interface, the standard Gibbs adsorption free energy was considered. The obtained results allow us to state that the concentration of both mixture components corresponding to their saturated monolayer and the surface tension of their aqueous solution can be predicted using the surfactants' single monolayer pressure and their mole fraction in the mixed monolayer determined in the proposed way.
Subject(s)
Water , Adsorption , Benzene Derivatives , Glycolipids/chemistry , Polyethylene Glycols/chemistry , Surface Tension , ThermodynamicsABSTRACT
Due to the increasing practical use of mixtures of flavonoids with nonionic surfactants the presented studies were based on the measurements of surface tension and conductivity of aqueous solution of the quercetin (Q) and rutin (Ru) in the mixtures with Triton X-114 (TX114) and Tween 80 (T80) as well as the contact angle of model liquids on the PTFE surface covered by the quercetin and rutin layers. Based on the obtained results components and parameters of the quercetin and rutin surface tension were determined and the mutual influence of Q and Ru in the mixtures with TX114 and T80 on their adsorption and volumetric properties were considered. It was found, among others, that based on the surface tension isotherms of the aqueous solution of the single flavonoid and nonionic surfactant, the surface tension isotherms of the aqueous solution of their mixture, the composition of the mixed monolayer at the water-air interface as well as the CMC of flavonoid + nonionic surfactant mixture can be predicted. The standard Gibbs energy, enthalpy and entropy of the adsorption and aggregation of the studied mixtures were also found, showing the mechanism of the adsorption and aggregation processes of the flavonoid + nonionic surfactant mixture.
Subject(s)
Flavonoids , Surface-Active Agents , Adsorption , Polysorbates , Quercetin , Rutin , Temperature , WaterABSTRACT
The studies on the adsorption properties and composition of the adsorbed monolayer at the water-air interface of the binary Kolliphor® ELP (ELP) and Kolliphor® RH 40 (RH40) mixtures based on the measurements of the surface tension (γLV) of their aqueous solution in the temperature range from 293 to 318 K were carried out. The γLV isotherms were described by the exponential function of the second order and the Szyszkowski equation as well as predicted by Fainerman and Miller equation. The obtained γLV isotherms were analyzed using the exponential function of the second order, the Szyszkowski, Fainerman and Miller as well as independent adsorption equations. The γLV isotherms were also used for determination of the Gibbs surface excess concentration of RH40, ELP and their mixture (Γ) at the water-air interface as well as the mixed monolayer composition. Based on Γ and the constant a in the Szyszkowski equation, the standard thermodynamic functions of adsorption were considered. From the consideration dealing with the γLV isotherms obtained by us, it results, among others, that these isotherms for the non-ideal solution of macromolecular surfactants mixture can be predicted using the Fainerman and Miller equation. From this consideration, it also results that a simple method proposed by us, based on the isotherms of RH40 and ELP, allows us to predict the composition of their mixed monolayer in the whole concentration range of RH40 and ELP in the bulk phase.
ABSTRACT
Measurements were made of the surface tension of the aqueous solutions of p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycols) having 10 oxyethylene groups in the molecule (Triton X-100, TX100) and cetyltrimethylammonium bromide (CTAB) with Zonyl FSN-100 (FC6EO14, FC1) as well as with Zonyl FSO-100 (FC5EO10, FC2) ternary mixtures. The obtained results were compared to those provided by the Fainerman and Miller equation and to the values of the solution surface tension calculated, based on the contribution of a particular surfactant in the mixture to the reduction of water surface tension. The changes of the aqueous solution ternary surfactants mixture surface tension at the constant concentration of TX100 and CTAB mixture at which the water surface tension was reduced to 60 and 50 mN/m as a function of fluorocarbon surfactant concentration, were considered with regard to the composition of the mixed monolayer at the water-air interface. Next, this composition was applied for the calculation of the concentration of the particular surfactants in the monolayer using the Frumkin equation. On the other hand, the Gibbs surface excess concentration was determined only for the fluorocarbon surfactants. The tendency of the particular surfactants to adsorb at the water-air interface was discussed, based on the Gibbs standard free energy of adsorption which was determined using different methods. This energy was also deduced, based on the surfactant tail surface tension and tail-water interface tension.
ABSTRACT
The adsorption of Zonyl FSN-100 (FSN100, having an average 14 oxyethylene units and 6 -CF2 groups) and Zonyl FSO-100 (FSO100, having an average 10 oxyethylene units and 5 -CF2 groups) as well as of their mixtures with p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycols) having 10, 16 and 8 oxyethylene groups in molecule (TX100, TX165, TX114) and cetyltrimethylammonium bromide (CTAB) at the solution-air and polytetrafluoroethylene (PTFE)-solution and polymethyl methacrylate (PMMA)-solution interfaces as well as the composition of the surface mixed layer was discussed based on the literature data. The adsorption properties of nonionic fluorocarbon surfactants were compared to those of the classical ones on the basis of the Gibbs standard free energy of adsorption determined by different ways and the intermolecular interactions of the surfactant molecules through the water phase. The synergetic effect in the reduction of the water surface tension by the mixture of fluorocarbon and classical nonionic surfactant was shown and explained by the comparison of the composition of the mixed surface layer to those in the bulk phase. The composition of the mixed fluorocarbon and classical surfactant layer at the solution-air interface was compared to that formed at the PTFE-solution and PMMA-solution interfaces. The changes of the surface tension of the aqueous solution of the fluorocarbon surfactants and their mixtures with classical hydrocarbon ones and their adsorption were analyzed taking into account the PTFE and PMMA surface wettability. This analysis was also based on the components and parameters of the head and tail of the surfactants surface tension as well as those of PTFE and PMMA. Apart from adsorption and wetting properties the aggregation of the fluorocarbon surfactants and their mixtures was discussed. A specific attention was paid to the possibility of two CMC values in the case of nonionic fluorocarbon surfactants as well as the synergism in CMC of mixtures of nonionic fluorocarbon and hydrocarbon surfactants.
ABSTRACT
The adsorption of methanol, ethanol and propan-1-ol at the solution-air and solid-solution interfaces, their aggregation in the aqueous media as well as wetting properties regarding their applications as additives or co-surfactants in the surfactants aqueous solution were discussed based on the literature data. Mutual influence of alcohols and surfactants on the solution-air and solid-solution interface tension was considered. For this purpose there were used different methods allowing to describe or predict changes of water surface tension as a function of alcohols concentration. These, in turn, as a function of alcohol and/or surfactant concentration were also analyzed by means of the methods applied for prediction of surface tension of aqueous solution of the classical surfactants mixture. The same considerations related to the behaviour of alcohol and surfactant at the solid-solution and solution-air interfaces were made. To explain the behaviour of alcohols and surfactants mixture at the solution-air and solid-solution interfaces the components and parameters of water, alcohols, surfactants and solids surface tension as well as the Gibbs free energy changes during the adsorption process were taken into account. It was proved that wettability of some solids can be predicted based on alcohol and surfactants adsorption as well as surface tension components and parameters. As follows the mutual influence of alcohol and surfactant on their adsorption at the solution-air and solid-solution interfaces as well as on the wetting properties at the alcohol concentration from zero to its critical aggregation concentration (CAC) is different from that at its concentration higher than CAC.
ABSTRACT
Measurements of the surface tension of aqueous solutions of polysorbates (Tween 20, Tween 60 and Tween 80) at 293, 303 and 313 K were made. On the basis of the obtained results the Gibbs surface excess concentration of the Tweens at the water-air interface and critical micelle concentrations were determined. Knowing the Gibbs surface excess concentration and taking into account the difference between the limiting area occupied by water and Tween molecules at the water-air interface, the fraction occupied by Tween molecules was established. The limiting area occupied by the Tween molecule was calculated by applying the Joos equation. The area determined in such a way was confirmed by the calculations of cross section of Tween molecules based on the bond lengths and the angles between them as well as the average distance between the molecules, taking into account their different conformations. This area was used for calculation of the standard Gibbs energy of adsorption using the Langmuir equation. The standard Gibbs energy of Tweens adsorption at the water-air interface was also calculated from the hydrophobic part of Tween molecule-water interface tension and that of hydrophobic part. Using the determined values of standard Gibbs energy of adsorption at different temperatures, the standard enthalpy and entropy values were deduced. The standard thermodynamic functions of micellization were also determined and compared to the Gibbs energy of Tween molecules interactions through the water phase.
ABSTRACT
The adsorption of surfactants at the water-air and solid-water interfaces and their wetting properties decide their practical applications. Therefore the adsorption of monorhamnolipid, surfactin, n-octyl-ß-d-glucopyranoside, n-dodecyl-ß-d-glucopyranoside, n-dodecyl-β-d-maltoside, sucrose monodecanoate, sucrose monododecanoate, Tween 20, Tween 60, and Tween 80 at the water-air, polytetrafluoroethylene-water, polyethylene-water, poly(methyl methacrylate)-water, polyamide-water, and quartz-water interfaces, their tendency to form micelles as well as their wetting properties, were considered in the light of their microscopic properties. For this purpose, the components and parameters of the surfactant tail and head, water and solids surface tension, and surfactant contactable area with adherent medium were applied for prediction of surfactant-surfactant and surfactant-solid interactions through the water phase with regard to their adsorption, micellization, and wetting processes. Next, the Gibbs free energy of interactions was compared to the Gibbs free energy of surfactant adsorption at the water-air and solid-water interfaces as well as the micellization. It appeared that from the surfactant-surfactant and surfactant-solid interactions through the water phase determined on the basis of the tail and head of surfactant surface tension, it is possible to predict the surfactant tendency to adsorb at the water-air and solid-water interfaces, as well as to form micelles.
Subject(s)
Polymers/chemistry , Surface-Active Agents/chemistry , Adsorption , Polysorbates/chemistry , Surface Tension , WettabilityABSTRACT
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.
ABSTRACT
Measurements of the surface tension, density and viscosity of sodium dodecyl sulfate (SDS) and rhamnolipid (RL) mixtures were carried out in aqueous solution. From the obtained results, composition of mixed surface layer at the water-air interface, mixed micelles, parameter of intermolecular interactions, activity of SDS and RL in the surface layer and micelles, Gibbs standard free energy of adsorption and micellization as well as Gibbs free energy of SDS and RL mixing in the surface layer and micelles were established. These parameters were discussed in the light of independent adsorption of SDS and RL and the size of their molecules as well as the area in contact with water molecules. A correlation between the number of water molecules in contact with those of SDS and RL and standard free energy of adsorption as well as micellization of these surfactants was observed. A correlation between the apparent and partial molar volumes of RL and SDS in their mixture and size of surfactant molecules as well as the average distance between molecules was also found. The parameter of intermolecular interactions indicates that there is a synergetic effect in the reduction of water surface tension and micelle formation.
ABSTRACT
MEASUREMENTS: of the surface tension, density, viscosity and conductivity of aqueous solutions of rhamnolipid at natural and controlled pH were made at 293 K. On the basis of the obtained results the critical micelle concentration of rhamnolipid and its Gibbs surface excess concentration at the water-air interface were determined. The maximal surface excess concentration was considered in the light of the size of rhamnolipid molecule. Next the Gibbs standard free energy of rhamnolipid adsorption at this interface was determined on the basis of the different approaches to this energy. The standard free energy of adsorption was also deduced on the basis of the surface tension of n-hexane and water-n-hexane interface tension. Standard free energy obtained in this way was close to those determined by using the Langmuir, Szyszkowski, Aronson and Rosen, Gu and Zhu as well as modified Gamboa and Olea equations. The standard free energy of rhamnolipid adsorption at the water-air interface was compared to its standard free energy of micellization which was determined from the Philips equation taking into account the degree of rhamnolipid dissociation in the micelles.
Subject(s)
Glycolipids/chemistry , Water/chemistry , Adsorption , Air , Hexanes/chemistry , Hydrogen-Ion Concentration , Micelles , Solutions , Surface Tension , Temperature , Thermodynamics , ViscosityABSTRACT
Measurements of the surface tension, density and viscosity of aqueous solutions of n-oktyl-ß-D-glucopiranoside (OGP) were made at 293 K. From the obtained results the Gibbs surface excess concentration of OGP at the water-air interface and its critical micelle concentration were determined. The Gibbs surface excess concentration of OGP used in the Gu and Zhu isotherm equation allowed us to determine the Gibbs standard free energy of OGP adsorption at the water-air interface. The Gibbs standard free energy of OGP adsorption was also determined on the basis of the Langmuir, Szyszkowski, Gamboa and Olea equations as well the surface tension of "hydrophobic" part of OGP and "hydrophobic" part-water interface tension. It appeared that there is an agreement between the values of Gibbs standard free energy of OGP adsorption at the water-air interface determined by using all the above mentioned methods. It also proved that standard free energy of OGP micellization determined from CMC is consistent with that obtained on the basis of the free energy of the interactions between the "hydrophobic" part of the OPG through the water phase.
Subject(s)
Glucosides/chemistry , Micelles , Adsorption , Air , Solutions , Surface Tension , Thermodynamics , Viscosity , WaterABSTRACT
The contact angle measurements of the aqueous solutions of p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycol) (TX-100) and cetyltrimethylammonium bromide (CTAB) mixture with ethanol on polytetrafluoroethylene (PTFE) and poly (methyl methacrylate) (PMMA) were carried out in the range of the total concentration of TX-100 and CTAB mixture from 1×10(-6) to 1×10(-3) M and in the whole range of ethanol concentration. In the surfactant mixture, the mole fraction of TX-100 was equal to 0.2; 0.4; 0.6 and 0.8, respectively. From the obtained results, the critical surface tension of PTFE and PMMA wetting and the adhesion work of the solutions to the polymer surface were established. The PMMA surface tension was calculated from the Neumann's equation. It appeared that for the ethanol concentration higher than that corresponding to the association of its molecules, the surface tension of PMMA calculated from the Neumann's equation is close to the critical surface tension of PMMA wetting. It also appeared that it is possible to predict the work of adhesion of the studied solutions to the PMMA surface by using the PMMA surface tension data determined on the basis of the van Oss et al. approach to the interfacial tension and those from the Neumann's equation.