Contact Angles Of Aqueous Solutions Research Articles

Effect of Spontaneous and Water-Based Passivation on Components and Parameters of Ti6Al4V (ELI Grade) Surface Tension and Its Wettability by an Aqueous Solution of Sucrose Ester Surfactants

Solid wettability is especially important for biomaterials and implants in the context of microbial adhesion to their surfaces. This adhesion can be inhibited by changes in biomaterial surface roughness and/or its hydrophilic–hydrophobic balance. The surface hydrophilic–hydrophobic balance can be changed by the specifics of the surface treatment (proper conditions of surface preparation) or adsorption of different substances. From the practical point of view, in systems that include biomaterials and implants, the adsorption of compounds characterized by bacteriostatic or bactericidal properties is especially desirable. Substances that are able to change the surface properties of a given solid as a result of their adsorption and possess at least bacteriostatic properties include sucrose ester surfactants. Thus, in our studies the analysis of a specific surface treatment effect (proper passivation conditions) on a biomaterial alloy’s (Ti6Al4V ELI, Grade 23) properties was performed based on measurements of the contact angles of water, formamide and diiodomethane. In addition, the changes in the studied solid surface’s properties resulting from the sucrose monodecanoate (SMD) and sucrose monolaurate (SML) molecules’ adsorption at the solid–water interface were also analyzed. For the analysis, the values of the contact angles of aqueous solutions of SMD and SML were measured at 293 K, and the surface tensions of the aqueous solutions of studied surfactants measured earlier were tested. From the above-mentioned tests, it was found that water environment significantly influences the components and parameters of Ti6Al4V ELI’s surface tension. It also occurred that the addition of both SMD and SML to water (separately) caused a drop in the water contact angle on Ti6Al4V ELI’s surface. However, the sucrose monolaurate surfactant is characterized by a slightly better tendency towards adsorption at the solid–water interface in the studied system compared to sucrose monodecanoate. Additionally, based on the components and parameters of Ti6Al4V ELI’s surface tension calculated from the proper values of components and parameters of model liquids, it was possible to predict the wettability of Ti6Al4V ELI using the aqueous solutions of SMD and SML at various concentrations in the solution.

Mutual influence of ethanol and surfactin on their wetting and adhesion properties

The measurements of the contact angle of aqueous solution of ethanol and surfactin mixture in the whole range of ethanol concentration on PTFE, PMMA and quartz were made at changing ethanol concentration and constant of surfactin and vice versa. Based on the obtained results, the Young-Dupre and van Oss et al. equations, the intermolecular interactions parameter between the solution and solid phases was determined and used to explain the possibility to form the ethanol and surfactin mixed layer beyond the solution drop settled on the PMMA and/or quartz surface. This layer pressure and that at the PMMA-solution, the quartz-solution interface was determined using the Young-Dupre and van Oss et al. equations and applied for the ethanol and surfactin Frumkin isotherm adsorption determination. The Gibbs adsorption isotherm was also determined. The ethanol and surfactin Gibbs and Frumkin isotherms at the solid-solution, solid-air interfaces were compared to those at the solution-air one. From these isotherms of surfactin and ethanol adsorption at three interfaces, the slope of the linear dependence between the adhesion and surface tension was explained. The Gibbs isotherm was applied for determination of the Gibbs standard free energy of ethanol and surfactin adsorption at the solid-air and solid-water interfaces.

Effects of catanionic surfactant mixture adsorption on the wettability of PTFE and PMMA

Surfactants can regulate the wettability of a liquid on a solid substrate as they adsorb to solid-liquid and gas-liquid interfaces. In the present work, a catanionic surfactant mixture, sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (C12TAB) mixed at a molar ratio of 2:1, showed outstanding synergistic effect in improving the wettability of low energy substrates (PTFE and PMMA). The adsorption behaviors of the catanionic surfactant mixture on PTFE and PMMA substrates were studied. The surface tensions and contact angles of aqueous solutions of SDS, C12TAB, and their mixture on PTFE and PMMA were measured, and the adhesion tension and adhesion work were calculated. Compared to individual SDS and C12TAB, the SDS-C12TAB mixture formed a compactly arranged layer at the PTFE-aqueous interface, thereby leading to a more significant hydrophilic modification of PTFE. In the PMMA system, the SDS-C12TAB mixture adsorbed to the PMMA-aqueous interface through acid-base interactions between the positively charged surfactant headgroups and the basic groups at PMMA surface and increased the hydrophobicity of the PMMA substrate at low surfactant concentrations. When the surfactant concentration exceeded the critical micelle concentration (CMC), the surfactant started to adsorb to the PMMA-aqueous interface through hydrophobic interactions between the hydrophobic surfactant tails and the nonpolar sites at PMMA surface, which further improved the wettability of PMMA. Overall, the wettability of low energy substrates can be significantly improved under the strong synergistic effect of commercial anionic and cationic surfactants without need of complex synthesis of new amphiphiles. Therefore, the catanionic surfactant mixtures may be a very promising system for regulating wettability.

Advances in Surfactants in Foliar Application of Agrochemicals on Mango Leaf Surfaces

Abstract The surface tension, pH and contact angle of the wetting liquid as well as the complex composition of the leaf surface are important parameters to describe the spreading, wettability and absorption of agrochemicals on the leaf surfaces. The contact angle of aqueous solutions of agrochemicals (multi-micronutrient fertilizers, growth regulator and insecticides) with/without Leaf guard, bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) and Sapindus mukorrossi (Ritha) were measured over the surface of mango leaves. The order of contact angle (mean) values was found to be AOT < Ritha < Leaf guard, which implies that AOT is a better wetting agent, but Ritha has a higher range of adhesion work because of its acidic nature (low pH). The wetting free energy was found to be more negative in the presence of Leaf guard, Ritha and AOT than in water, which indicates that wetting is more spontaneous in the presence of surfactants. The adaxial surface of mango leaves had a higher surface free energy than the abaxial part and hence showed higher wettability than the abaxial part.

Wetting properties of Saponaria officinalis saponins

The contact angles of water, formamide and diiodomethane on the polytetrafluoroethylene (PTFE), poly(methyl methacrylate) (PMMA) and quartz covered with Saponaria officinalis saponins and pure hederagenin films as well as the contact angles of aqueous solutions of saponins on the PTFE, PMMA and quartz surface, were measured. The adsorption of the saponins at the solid-water interface was also compared to that at the water-air one. The possibility to adsorb the saponins at the solid-water interface was analyzed on the basis of the Gibbs standard free energy of adsorption relative to the Gibbs free energy of interactions of saponins molecule with solid surface through the water phase. The changes in the solid-water and water-air interface tension under the influence of saponins adsorption were considered in the light of the PTFE, PMMA and quartz wettability by the aqueous solution of saponins. From this consideration it results that the contact angle of aqueous solution of saponins on PTFE, PMMA and quartz surface as well as the adhesion work of these solutions to solid can be predicted on the basis of the components and parameters of the water, solid and solution surface tensions. Experiments indicated that saponins are poor wetting agents and the adhesion work of the saponins solution does not depend on their concentration.

Effect of Polysorbates on Solids Wettability and Their Adsorption Properties

The wettability of solids is important from both practical and theoretical viewpoints. In this study, we measured the contact angle of aqueous solutions of polysorbates (Tween 20, Tween 60, and Tween 80) on polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), polyamide (nylon 6), and quartz. Based on the obtained results, the adsorption of Tween 20 (T20), Tween 60 (T60), and Tween 80 (T80) at the solid-water interface was determined based on the structure and size of their molecules. Next, the tendency of polysorbates to adsorb at the solid-water interface was considered based on the Gibbs standard free energy of adsorption (ΔGadso). This energy was evaluated using various methods, including a method we propose based on the critical micelle concentration (CMC) and the contact angle of water and solution at the CMC, as well as their surface tension. The ΔGadso values obtained by this method were comparable to those calculated from the Langmuir equation. Taking into account the Tweens tendency to adsorb at the solid-water interface, the measured contact angle, the components and parameters of surface tension of Tweens solutions and solids, and the surface tension of water and its Lifshitz-van der Waals component that we determined, the wetting process in the solid-solution drop-air system was analyzed. The results based on the mentioned parameters showed that it is possible to predict the wettability of apolar, monopolar, and bipolar solids using the aqueous Tweens solution and their solution adhesion.

Wettability and Adhesion Work Prediction in the Polymer–Aqueous Solution of Surface Active Agent Systems

The wettability of solids by aqueous solutions of surfactants is very important in many practical applications. Thus, the measured advancing contact angles of aqueous solutions of chosen surfactants on polyethylene (PE) and those taken from the literature on polytetrafluoroethylene (PTFE), poly(methyl methacrylate) (PMMA), and polyamide (nylon 6) were analyzed. Based on the measured values of the contact angles and the literature data of the surface tensions of the studied surfactant solutions, their adsorption at the PE–water interface and the work of adhesion (Wa) were determined. The values of Wa to PE calculated on the basis of the contact angles and surface tensions of these solutions were compared to those determined by applying the new Lifshitz–van der Waals component of the water–PE surface tension. There was a good agreement between the Wa values determined in two different ways. Their contact angles were calculated using the values of PE surface tension, the new Lifshitz–van der Waals component of the water surface tension, and the surface tension of aqueous solutions of the studied surfactants. The contact angle values calculated in such a way were close to the measured values. In the case of PTFE, the same relations were obtained. The values of Wa to PMMA and nylon 6 could be also predicted.

Surface tension of polytetrafluoroethylene and its wetting by aqueous solution of some surfactants and their mixtures

Measurements of the contact angle of aqueous solution of rhamnolipid (RL) mixture with n-octyl-β-d-glucopyranoside (OGP), Triton X-100 (TX-100) or/and sodium dodecylsulfate (SDDS) on polytetrafluoroethylene (PTFE) were made. To this aim there was used a plate whose surface topography was analyzed by means of optical profilometry method. Additionally, plate surface chemistry was studied employing the Fourier transform infrared spectroscopy. The obtained values of contact angle were discussed based on the PTFE surface tension (γSV) as well as the Lifshitz-van der Waals component of the water surface tension (γWLW). The contact angle of aqueous solution of several surfactants and their mixtures on PTFE was also considered on the basis of γSV and γWLW. It occured that by using the values of γSV, γWLW and surface tension of the aqueous solution of surfactants and their mixtures, the contact angle on PTFE can be predicted. It also occured that changes of adhesion tension of aqueous solutions of surfactants as a function of their concentration can be determined by the exponential function of the first or second order. Using such functions Gibbs surface excess concentration of surfactants at the PTFE-water interface, mole fraction of surfactant in the mixed monolayer and fraction of the area occupied by given surfactants in the monolayer were determined. Gibbs surface free energy of adsorption of a given surfactant in the presence of another one and adhesion work of the aqueous solution of surfactants to the PTFE surface were also evaluated.

Fabrication on low voltage driven electrowetting liquid lens by dip coating processes

A low voltage driven electrowetting on dielectric liquid focus lens was fabricated based on a tiny glass tube which had been coated with ITO (indium tin oxide)–Al2O3–TiO2–Teflon multilayered thin films on the inside. Method of sol–gel/chemical solution dip coating was used for the film preparation. A cambered interface between silicon oil and aqueous solution containing NaCl and sodium dodecyl sulfate (SDS) was used for the lens refraction. The curvature of the interface was adjusted by changing the applied voltage. The contact angle of aqueous solution in oil atmosphere was reduced from 155° to 67° when −10V DC was applied. The leakage current was only 28nA at that applied voltage and its focal length changed from −2mm to infinity then to 10mm.

Wetting and adsorption properties of cetyltrimethylammonium bromide and Triton X-100 mixture with short-chain alcohol in polymer–solution–air system

Measurements of the contact angle of the aqueous solutions of Triton X-100 (TX-100) and cetyltrimethylammonium bromide (CTAB) mixture with methanol or propanol on the polytetrafluoroethylene (PTFE) and nylon-6 surfaces were made. On the basis of the obtained results, the Gibbs surface excess concentration of alcohol and TX-100 + CTAB mixture at the polymer–solution and polymer–air interfaces was calculated and compared to that at the solution–air one. The standard Gibbs free energy of alcohol adsorption was determined by different methods. For TX-100 and CTAB mixture, this energy was calculated using the values of critical micelle concentration (CMC) of that mixture, the surface tension and contact angle of aqueous solution of alcohol as well as the surface tension and contact angle of the aqueous solution of TX-100 and CTAB mixture with alcohol at CMC. The polymer–solution interfacial tension, the adhesion tension, and the adhesion work of the studied solutions to the polymer surface were also determined. From the obtained data, it results that the studied solutions can wet completely only the nylon-6 surface and that below alcohol critical aggregation concentration the adsorption of surfactants and alcohols at the polymer–water and water–air interfaces is similar for PTFE and different for nylon-6.

Synthesis and aggregation behaviors of tail-branched surfactant Guerbet-cetyl trimethyl ammonium chloride

A novel cationic surfactant Guerbet-cetyl trimethyl ammonium chloride (G-CTAC) was synthesized by combining several traditional synthetic processes in laboratory. The molecular structure of G-CTAC was characterized by Fourier transform infrared (FT-IR) spectra and proton nuclear magnetic resonance (1HNMR). This new amphiphile exhibited excellent performances in aqueous solution, which was investigated by surface tension measurement, contact angle on parafilm, particle size of aggregates, transmission electron microscopy (TEM), emulsifying experiments, and antistatic tests. It was found that the new quaternary ammonium compound could effectively decrease the surface tension of aqueous solution to 26.2 mN m−1 with the critical micelle concentration (CMC) being 5.9 mmol L−1. In addition, the cationic surfactant synthesized could efficiently decrease the contact angle of aqueous solution on paraffin surface. We suppose that these unique properties are attributed to the presence of the branching Guerbet-cetyl being hydrophobic group in the molecule. Moreover, according to TEM observations, this quaternary ammonium compound was inclined to aggregate into vesicles spontaneously without induction of any other additives in aqueous solution. Antistatic tests and emulsifying experiments were also conducted to explore the potential applications of this new material.

Adsorption and wetting properties of cationic, anionic and nonionic surfactants in the glass-aqueous solution of surfactant-air system

The measurements of the advancing contact angle for water, formamide, glycerol, diiodomethane and aqueous solutions of Triton X-100 (TX-100), Triton X-165 (TX-165), sodium decylsulfate (SDS), sodium dodecylsulfate (SDDS), hexadecyltrimethylammonium bromide (CTAB) and hexadecylpyridinium bromide (CPyB) on the glass surface were carried out. Using the values of the contact angle of these liquids and solutions, the glass surface free energy as well as its components and parameters were determined. This energy, its components and parameters were used for interpretation of the glass wettability by the surfactants solutions in the light of the surfactants adsorption in the three-phase systems and the adhesion of the solution to the glass surface. It appeared that the surface free energy of glass determined from the contact angle of aqueous solution of surfactants on its surface is useful for the determination of the Gibbs surface excess concentration of surfactant at the glass–air and glass–solution interfaces and consequently, the Gibbs standard free energy of surfactant adsorption at these interfaces. It also appeared that by using the Neumann et al. and van Oss et al. equations, it is possible to predict the work of adhesion of aqueous solution of surfactant to the glass surface.

Wetting and Adsorption Properties of Aqueous Solutions of Ternary Mixtures of Hydrocarbon and Fluorocarbon Nonionic Surfactants in PTFE-Solution–Air Systems

The surface tensions and contact angles of aqueous solutions of ternary mixtures of hydrocarbon, TX100 and TX165, and fluorocarbon, FSN100, surfactants at different mole fractions in the bulk phase on a poly(tetrafluoroethylene) (PTFE) surface were studied. The measured values were used in the Young equation for calculations of the polymer–solution interfacial tension in two ways, first, assuming that the surface tension of PTFE is constant and, second, assuming that this tension is not constant and is equal to the value determined for FSN100 at a given concentration. Next, the Gibbs surface excess concentrations of the studied mixtures at the polymer–solution interface were calculated and compared to the corresponding values at the solution–air interface. Also, the critical surface tension of polymer wetting was obtained from the relationship between the adhesion tension and the surface tension of aqueous solutions of the studied mixtures and then related to the adsorption of the surfactants at the water–air and PTFE–water interfaces.

The Effectiveness of Using Pulpotec® in Treatment of Pulpitis by Pulpotomy of Vital Deciduous Molar and Vital Immature Permanent Molar

Aims: To evaluate the effect of two types of disinfectant solutions(2% alkaline glutaraldehyde, 1% sodium hypochlorite) in wettability of three types of elastomeric impression materials (light body) which are used in crown and bridge restorations at different times of immersion. Materials and me-thods: Three types of elastomeric impression materials (light body) were formed on a flat acrylic resin block and allowed to set(five specimens of each impression material was done for each immersion time(15,30 and60 minutes)of each disinfectant solution in addition to control groups). The wettability is indicated by measuring the contact angle of aqueous solution of CaSO4 on surface of cured impres-sion materials. Results: indicated no significant effect of immersion times on wettability of three types of impression materials. The hydrophilic type produce high wettability. Conclusions: The disinfectant solutions have different effects on each impression material. Sodium hypochlorite has the greatest beneficial effect on wettability

Wettability, adhesion, adsorption and interface tension in the polymer/surfactant aqueous solution system. I. Critical surface tension of polymer wetting and its surface tension

The contact angle of aqueous solutions of Triton X-100, Triton X-114, Triton X-165, sodium dodecylsulfate, sodium hexadecylsulfonate, cetyltrimethylammonium bromide, cetylpyridinium bromide, sodium N-lauryl sarcosinate, dodecyldimethyethylammonium bromide, tetradecyltrimethylammonium bromide and benzyldimethyldodecylammonium bromide on polytetrafluoroethylene, polymethyl methacrylate and nylon 6 was studied. The contact angle values were used in the Young equation for the polymer–solution interface tension calculation and for the determination of the critical surface tension of polymer wetting. The critical surface tension of polymer wetting was obtained on the basis of the relationship between the cosine of contact angle and/or the adhesion tension as a function of the surface tension of aqueous solution of studied surfactants and then was discussed in relation to the Lifshitz–van der Waals components and electron-acceptor and electron-donor parameters of polytetrafluoroethylene, polymethyl methacrylate and nylon 6 surface tension. The role of the parameter of interfacial interactions in the relationship between the critical surface tension of polymer wetting and the surface tension was also considered. This parameter was calculated by using the polymer–solution interface tension as well as the polymer and aqueous solutions of surfactant surface tension.

Contact Angle of Ethanol and n-Propanol Aqueous Solutions on Metal Surfaces

The contact angles of the aqueous solution of ethanol and that of n-propanol on copper, aluminum, and stainless steel surfaces are reported. The contact angles were measured under atmospheric conditions, and then under vapor-liquid equilibrium conditions at 1 atm and different temperatures. The results showed the variations of the contact angles with the concentrations of aqueous solutions on different metal material surfaces with different roughness. Some unstable behavior of the wetting ability around the azeotropic point of a binary solution is reported. Influences of concentration, kind of materials, and the surface roughness on the wetting ability are discussed. The model for predicting the contact angle of alcohol aqueous solutions on metal surfaces under atmospheric and vapor-liquid two-phase equilibrium conditions at 1 atm is derived from the Young equation.

Multiparameter screening on SlipChip used for nanoliter protein crystallization combining free interface diffusion and microbatch methods.

This paper describes two SlipChip-based approaches to protein crystallization: a SlipChip-based free interface diffusion (FID) method and a SlipChip-based composite method that simultaneously performs microbatch and FID crystallization methods in a single device. The FID SlipChip was designed to screen multiple reagents, each at multiple diffusion equilibration times, and was validated by screening conditions for crystallization of two proteins, enoyl-CoA hydratase from Mycobacterium tuberculosis and dihydrofolate reductase/thymidylate synthase from Babesia bovis, against 48 different reagents at five different equilibration times each, consuming 12 microL of each protein for a total of 480 experiments using three SlipChips. The composite SlipChip was designed to screen multiple reagents, each at multiple mixing ratios and multiple equilibration times, and was validated by screening conditions for crystallization of two proteins, enoyl-CoA hydratase from Mycobacterium tuberculosis and dihydrofolate reductase/thymidylate synthase from Babesia bovis. To prevent cross-contamination while keeping the solution in the neck channels for FID stable, the plates of the SlipChip were etched with a pattern of nanowells. This nanopattern was used to increase the contact angle of aqueous solutions on the surface of the silanized glass. The composite SlipChip increased the number of successful crystallization conditions and identified more conditions for crystallization than separate FID and microbatch screenings. Crystallization experiments were scaled up in well plates using conditions identified during the SlipChip screenings, and X-ray diffraction data were obtained to yield the protein structure of dihydrofolate reductase/thymidylate synthase at 1.95 A resolution. This free-interface diffusion approach provides a convenient and high-throughput method of setting up gradients in microfluidic devices and may find additional applications in cell-based assays.

Biochemically Responsive Smart Surface

A design of smart surfaces responsive to biochemical analytes is demonstrated in the example of mixed monolayers of biotin/fluorocarbon. The contact angle of aqueous solutions on such surfaces decreases upon streptavidin binding and can be used in detecting this protein. The specificity of the effect is confirmed by the lack of a contact angle change by streptavidin blocked with biotin and by bovine serum albumin.

Wetting properties of aqueous solutions of hydrophobically modified inulin polymeric surfactant

The contact angles of aqueous solutions of a polymeric surfactant namely hydrophobically modified inulin (INUTEC®SP1) were measured on hydrophilic and hydrophobised quartz glass surfaces using the sessile drop technique. These measurements showed a large difference (>10°) between the advancing contact angle θ1 (that is measured immediately after placing the drop on the surface) and the constant contact angle θ2 (that is measured 30 minutes after placing the drop). In all the results only the contact angle θ2 was subsequently measured. θ versus INUTEC®SP1 concentration Cs curves were obtained at various NaCl concentrations both on hydrophilic and hydrophobic glass surfaces. On hydrophilic glass surface the θ versus Cs curves showed a maximum at a concentration range of 10–6 to 2 × 10–5 mol dm-3 INUTEC®SP1. These curves were shifted to lower values as the NaCl concentration was increased. On such hydrophilic surface the INUTEC®SP1 molecule adsorbs with the polyfructose loops and tails oriented towards the surface leaving the alkyl chains in solution. Saturation adsorption with this orientation occurs at 2 × 10–5 mol dm-3 INUTEC®SP1. However, the contact angles remain quite small ( 2 × 10–5 mol dm-3θ decreases with further increase of the INUTEC®SP1 concentration reaching 5° at the Critical Association Concentration (CAC) of the polymer. This indicates the formation of a bilayer of INUTEC®SP1 molecules with the alkyl chains hydrophobically attached to those of the first layer. On a hydrophobic glass surface, adsorption of INUTEC®SP1 occurs by multi-point attachment with the alkyl chains on the surface leaving the hydrophilic polyfructose loops and tails dangling in solution. This results in a gradual decrease of the contact angle with increase in INUTEC®SP1 concentration, reaching a plateau value (>85°) between 2 × 10–5 and 2 × 10–4 mol dm-3. The large contact angles obtained on adsorption of the polymeric surfactant on a hydrophobic surface indicate the presence of several uncovered hydrophobic patches. These results give a reasonable picture of the adsorption and orientation of the INUTEC®SP1 molecules on both hydrophilic and hydrophobic solid surfaces.

The wettability of polytetrafluoroethylene and polymethyl methacrylate by aqueous solution of two cationic surfactants mixture

Advancing contact angle ( θ) measurements were carried out for aqueous solutions of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPyB) mixtures on polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA). The obtained results indicate that the wettability of PTFE and PMMA by aqueous solutions of CTAB and CPyB mixtures depends on the composition and concentration of the mixture; however, synergism in the wettability does not exist. In the range of low concentrations of aqueous solution mixtures there is a linear dependence between the contact angle and composition of the mixtures, but at a concentration close to CMC a deviation from linear dependence is observed. In contrast to Zisman, there is no linear dependence between cos θ and the surface tension of aqueous solution of CTAB and CPyB mixtures, but a linear dependence exists between the adhesional and surface tension, and these lines have a slope −1 and −0.34 for PTFE and PMMA, respectively, which suggests that adsorption of CTAB and CPyB mixtures at water–air and PTFE–water is the same, and the orientation of the CTAB and CPyB molecules at both interfaces in the saturated monolayer should also be the same. Adsorption of these mixtures at water–air interface is considerably higher than at PMMA–water interface, and CTAB and CPyB molecules should be parallelly oriented to PMMA surface in the saturated monolayer. Extrapolation of the straight lines to the points corresponding to the surface tension of aqueous solution, which completely spreads over the PTFE and PMMA surface, gives a critical surface tension of wetting equal to 23.44 and 33.13 mN/m, respectively. The value of 23.44 mN/m is higher than that of the surface tension of PTFE, but the value of 33.13 is lower than that of Lifshitz–van der Waals components of PMMA surface tension. On the basis of the critical surface tension, the surface tension of PTFE and PMMA, the Young equation, and thermodynamic analysis of the adhesion work of aqueous solution of surfactant to polymer surface, it was found that for PTFE and PMMA the changes of the contact angle of aqueous solution of two cationic surfactants mixtures on their surfaces as a function of the solution concentration resulted only from the decrease of the polar component of the solution surface tension.