Guy Broze | Université de Liège (original) (raw)

Papers by Guy Broze

The emergence of new flexible and wearable technologies should be performed with environmental an... more The emergence of new flexible and wearable technologies should be performed with environmental and safety considerations1. To meet these challenging aspects, this research focused on a new aqueous slurry formulation for the preparation of flexible and free-standing electrodes for Li-ion batteries. Carbon black, polyvinyl alcohol (PVA) and polyethylene glycol (PEG) were added to the active material. The anode material Li4Ti5O12 was chosen to develop this aqueous system thanks to it compatibility with aqueous process. The PVA/PEG ratio was optimized to obtain flexible and self-sustained electrodes after drying of the suspensions. The DSC (differential scanning calorimetry) measurements demonstrate the interaction between PVA and PEG polymers chains. SEM show good dispersion of all components within the electrodes. The PEG 6000 based electrodes displayed excellent electrochemical performances: up to 90% of the theoretical capacity at high current density (1C rate), which is comparable to the performances reported in the literature for flexible LTO electrode containing either CNTs or metallic current collector. Mild mechanical stress applied to the electrodes allowed to enhance the electrochemical performances. This could be related to the creation of tiny cracks leading to better penetration of the electrolyte in the electrode[2]. References 1- A.Vlad et al., Adv. Energy Mater. 2015, 5, 1402115 2- C. Piffet et al., Chem. Eng. J., 2020, 397, 125508Peer reviewe

Chemical Engineering Journal, 2020

processing of flexible, free-standing Li 4 Ti 5 O 12 electrodes for Li-ion batteries,

Polymer Bulletin, 1981

Halato-telechelic polymers (HTP) resulting from the neutralization of carboxy telechelic polymers... more Halato-telechelic polymers (HTP) resulting from the neutralization of carboxy telechelic polymers behave as useful ion-containing model compounds. Carboxy telechelic polybutadiene (Mn : 4,600) neutralized by magnesium methoxide exhibits a secondary relaxation mechanism characteristic of the ionic component. The activation process of this secondary relaxation obeys to an Arrhenius-type dependence and an activation energy of 30.5 Kcal/mole is calculated.

Journal of Colloid and Interface Science, 2001

The interaction of polyvinylpyrrolidone (PVP) with an anionic surfactant (sodium dodecyl sulfate,... more The interaction of polyvinylpyrrolidone (PVP) with an anionic surfactant (sodium dodecyl sulfate, SDS), a nonionic surfactant (pentaethylene glycol monodecyl ether, C 10 E 5), and a zwitterionic surfactant (lauryl amido propyl betaine, LAPB) has been investigated by means of pulsed gradient spin-echo NMR (FT-PGSE NMR), allowing self-diffusion coefficients to be determined. The results confirm the strong interaction prevailing in the PVP/SDS system, whereas no association has been observed in the PVP/C 10 E 5 and PVP/LAPB systems. Mixing PVP with two surfactants, namely SDS and C 10 E 5 or SDS and LAPB, results in the formation of ternary aggregates between the polymer and the mixed micelles.

Langmuir, 2000

Instability driven by diffusion flux across an asymmetric liquid film is theoretically investigat... more Instability driven by diffusion flux across an asymmetric liquid film is theoretically investigated. To specify the system, we consider an oil-water-air film; the transported species are oil molecules. The latter are dissolved (solubilized) at the oil-water interface, then they are transferred by diffusion across the aqueous film to the water-air interface, where they penetrate between the tails of adsorbed surfactant molecules. Fluctuational capillary waves at the two film surfaces are considered. The set of theoretical equations is solved to derive a dispersion relation between the wavenumber and the exponent of wave growth. The results reveal that if a local decrease in the film thickness appears, the water-air interface enters a zone enriched in dissolved oil. The newly adsorbed oil creates a surface tension gradient, which carries water away and causes a further decrease of the local film thickness in the concave zone, until eventually the film ruptures. The numerical results show that the film becomes less stable when its thickness decreases, its radius increases, and the diffusion flux across it is more intensive. Even very small decrements of the water-air surface tension, caused by the adsorbed oil, are sufficient to trigger the instability. Its appearance is not so sensitive to the degree of mobility of the oil-water interface. If the water-air surface is preequilibrated with the transported component (there is prespread oil), then the surface tension decrement and the instability disappear. The rupture of an asymmetric oil-water-air film is a precondition for entry of an oil drop at the water-air interface and effectuation of its foam-destructive action. Our results about a specific source of film instability could be helpful for a deeper understanding of the mechanisms of antifoaming.

Langmuir, 1997

We present experimental data showing that the surface tension, σ, of anionic surfactant (sodium d... more We present experimental data showing that the surface tension, σ, of anionic surfactant (sodium dodecyl dioxyethylene sulfate: SDP-2S) solutions undergoes a substantial change in the vicinity of the transition from sphere to cylinder in the micelle shape. The formation of cylindrical (rodlike) micelles at relatively low surfactant concentrations (between 2 and 8 mM) is promoted by the presence of Al 3+ ions in the solution. In the experiments we fixed the ionic strength of the added electrolyte but varied the molar fractions of NaCl and AlCl3. We established that the observed variation of σ in a vicinity of the sphereto-rod transition can be attributed to two competitive effects: (i) competition between Na + and Al 3+ counterions for the adsorption in the subsurface Stern layer and (ii) competition between the solution surface and the surfaces of the micelles to adsorb the Al 3+ counterions. The concentration of free Al 3+ ions in the solution is substantially reduced due to binding of Al 3+ to the micelles. The latter effect is studied experimentally by means of ultrafiltration experiments. We develop a theoretical model that allows us to calculate the true bulk (background) concentrations of Na + and Al 3+ ions, and the variation of σ in the vicinity of the sphere-to-rod transition. Good agreement between theory and experiment is achieved. The results show that the transition from sphere to cylinder in the micelle shape can be detected from the plot of the surface tension vs the surfactant-to-Al 3+ ratio. The paper also contains experimental data for the dependence of the CMC and surface tension of SDP-2S solutions on the ionic strength, which may represent independent interest.

Langmuir, 1997

The motion of the front between thick and thin foam film formed in a vertical frame is studied bo... more The motion of the front between thick and thin foam film formed in a vertical frame is studied both experimentally and theoretically. In the experiments we used sodium dodecyl sulfate solutions with added NaCl. The rate of motion of the front turns out to be constant for a given electrolyte concentration. Other important quantities that are measured are the thickness of the black film and the jump of the film tension, when the front reaches the bottom meniscus. The rate of the front turns out to be proportional to the jump of the film tension irrespective of the amount of added electrolyte. The theoretical model we developed allows quantitative interpretation of the experimental data. It is demonstrated that the motion of the front "thick-thin" film is accompanied with the formation of microscopic steady capillary waves in the transition zone. We show that the energy dissipation in the film is concentrated mainly into the latter part of the transition zone. The study can be helpful for the understanding of the mechanism of the foam films drainage as related to the stability of foams.

Langmuir, 1998

To study the electric properties of adsorption monolayers of an amphoteric surfactant, in our cas... more To study the electric properties of adsorption monolayers of an amphoteric surfactant, in our case lauryl dimethyl amine oxide (LDAO), we measured the-potential of latex particles covered with this surfactant. Its adsorption on the latex particles is estimated by dynamic surface tension measurements coupled with light scattering experiments. The influence of pH, ionic strength, and surfactant concentration on the electric properties of the adsorption monolayer has been examined. We propose a theoretical model which describes the dependence of-potential on both pH and the ionic strength. The model accounts for the adsorption of H + , Na + , and Clions on the amphoteric surfactant headgroups. Very good agreement between theory and experiment is achieved. The-potential measurements, coupled with the theoretical model, can be considered as a method for quantitative characterization of the ionization properties of amphoteric surfactants in adsorption layers. The latter properties are, in general, different from the surfactant ionization properties in the bulk of solution. We hope this approach can find application for characterizing various formulations used in the house hold and personal-care detergency, foaming, emulsification, etc.

Journal of Colloid and Interface Science, 1996

A theoretical approach to the kinetics of adsorption on the expanding interface of a micellar sur... more A theoretical approach to the kinetics of adsorption on the expanding interface of a micellar surfactant solution is proposed. For example, it can be the Langmuir adsorption isotherm The nonlinear partial differential equations of mass transfer of the micelles and monomers are reduced to ordinary differential equations, which are solved numerically along with the nonlin-c 10 (t) b Å G(t) G ϱ 0 G(t) , [1.2] earized adsorption isotherm as a boundary condition. Being more general, this theoretical approach is consistent also with the special case of small deviations from equilibrium widely used in the kinetwhere b and G ϱ are constants and t denotes time. Both nonics of micellization. The theory is applied further to fit the experiionic (3-5) and ionic (6) surfactants are found to comply mental data for dynamic surface tension of micellar solutions of with the Langmuir adsorption isotherm. More sophisticated sodium dodecyl sulfate and sodium polyoxyethylene-2 sulfate adsorption isotherms are also used (7). In some particular measured by the maximum bubble pressure (MBP) method. The cases (small adsorption, small deviations from equilibrium, expansion of the bubble surface is accounted for by using the etc.) the adsorption isotherm can be linearized and then stanexperimental dependence of the bubble size on time. The calcudard mathematical methods can be applied to solve the diffulated effective rate constant of micelle decay for sodium dodecyl sion problem, see e.g., Refs. (8-10). However, the general sulfate turns out to be sensitive to the mechanism of the micelle's boundary problem is essentially nonlinear. One way to solve disintegration. This provides a possibility for one to determine the it is to use perturbation series methods (11). Another aprate constants of the fast and slow processes in the relaxation kinetics of micellization by using a relatively simple experimental proach is to solve numerically the respective set of equations, technique for dynamic surface tension measurement like the MBP including the partial differential equation of diffusion (12, method.

Journal of Colloid and Interface Science, 1998

The great importance of foams in various fields of practice films and the decay of foams stabiliz... more The great importance of foams in various fields of practice films and the decay of foams stabilized with sodium dodecyl sulfate has stimulated studies of foam systems for many years (1). (SDS) is investigated. The ionic strength was kept constant, 0.024 The stability and the lifetime of foams are governed by the M, in all experiments. Sodium salts, Na 2 SO 4 , NaNO 3 , NaCl, Na 2 CO 3 , Na 3 PO 4 , and sodium citrate, as well as magnesium salts, properties of their structural units: thin liquid films (TLF) MgSO 4 , Mg(NO 3) 2 , MgCl 2 , and Mg(OOCCH 3) 2 , are used. The and Plateau borders (1-3). The latter are influenced by the lifetime and the critical thickness of rupture of the unstable films, rheological properties of the surfactant adsorption monoas well as the equilibrium thickness of the stable films, are mealayers and their interaction across the TLF. The electrostatic sured. The rate of drainage of the liquid from the foams and interaction, which gives rise to long-range double-layer their decay time are also measured. The influence of the bivalent forces (2) and to short-range hydration repulsion (4), plays counterion, Mg 2/ , is related to two major effects influencing the an important role in the stability of foam films. The effect film stability in the opposite directions: (i) increase of the surface of electrostatics was studied experimentally by variation of elasticity and viscosity due to connections between neighboring electrolyte concentration (2, 5, 6). Sharma and Khilar (7) surfactant headgroups produced by Mg 2/ and (ii) enhancement established that the addition of electrolyte affects the surface of the ionic correlation attraction between the film surfaces. The mobility. As a rule 1:1 electrolytes were used in these studdata show also an unexpectedly large influence of the co-ions on the film and foam stability. Carbonates, phosphates, and citrates ies. There are only few works on the effect of bivalent counhave the most significant stabilizing effect. At least two effects terions on the process of film thinning (8, 9). It was obmay be responsible for the larger stability of the films with co-ions served (9) that the type of film rupture depends to some of weak acids: (i) The dissolved carbonate and phosphate salts extent also on the type of co-ions. spontaneously adjust to pH 11.4 in the solution, which leads to The influence of co-ions (monovalent or bivalent) has hydrolysis of SDS to dodecanol. The latter increases the surface been studied mainly with respect to the properties of sodium elasticity, viscosity, and kinetic stability of films and foams. (ii) dodecyl sulfate (SDS) adsorption monolayers (10-12). Ya-The molecules of the carbonic, phosphoric, or citric acid can inmanaka (13) investigated the properties of vertical films and terconnect headgroups of neighboring SDS molecules in the surfoams containing sodium salts with various anions. These face adsorption monolayers by formation of multiple H-bonds. films and foams were stabilized by a nonionic surfactant Such a linking also enhances the kinetic stability. These hypotheses (polyoxyethylene nonylphenyl ether) instead of SDS. It was agree well with the accumulated experimental data and can be helpful for a better understanding of the role of citrates, phos-experimentally established that the stability of the studied phates, and other electrolytes in body-care and household defoams depends on the type of the anion in the solution. tergency.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999

We address the problem about the electro-diffusion-controlled adsorption from a submicellar solut... more We address the problem about the electro-diffusion-controlled adsorption from a submicellar solution of an ionic surfactant in the presence of a non-amphiphilic electrolyte (salt). We consider a disturbance of the surfactant adsorption layer, which is damped by the electro-diffusive transport of surfactant ions, counterions and coions. The evolution of the electric double layer with time is theoretically examined. The counterion adsorption (binding) is taken into account. Our purpose is to find the long-time asymptotic solution of the full electro-diffusion boundary problem. Assuming small perturbations the problem is linearized and a set of three differential operator equations is obtained. In the asymptotic case of long times these differential equations reduce to hypergeometric equations, whose solutions, fortunately, can be expressed in terms of elementary functions. As a result, explicit expressions for the characteristic relaxation times of the adsorptions of surfactant ions and counterions are obtained. Next we determine the characteristic relaxation time of surface tension, which is different from the adsorption relaxation time because of a specific contribution from the dynamic diffuse electric double layer. The thermodynamic parameters, entering the formula for the relaxation time, are expressed for various surfactant adsorption isotherms, those of Henry, Langmuir, Freundlich, Frumkin and van der Waals. The theory gives a quantitative interpretation of the experimental finding that the addition of salt accelerates the relaxation of the surface tension for the higher surfactant concentrations, but decelerates it for the lower surfactant concentrations. The results could be also useful for a theoretical interpretation of the processes in foams and emulsions under dynamic conditions.

Colloid and Polymer Science, 2003

Langmuir, 2003

The main target of this study is to develop a theoretical method for determining small contents o... more The main target of this study is to develop a theoretical method for determining small contents of dodecanol in samples of sodium dodecyl sulfate (SDS) by a detailed analysis of surface-tension isotherms. As a tool for our analysis, we employ the van der Waals model. Its application to data for alkanols and anionic surfactants gives an excluded area per adsorbed molecule equal to the geometrical area of the molecular cross section and adsorption energies consonant with Traube's rule. Because the dodecanol and SDS have different excluded areas, we extended the van der Waals model for the case of a two-component adsorption layer, with account for the counterion binding in the Stern layer. General expressions for the surface free energy, two-dimensional equation of state, surface chemical potentials, adsorption isotherms, and surface dilatational elasticity are derived. The experimental surface-tension isotherms are fitted by varying only one adjustable parameter. The model was successfully tested against data for solutions of SDS with a known content of dodecanol. Knowing the parameters of the model, we computed various properties of the surfactant adsorption layer. The results show that the presence of a small amount of dodecanol leads to a considerable increase of the total adsorption and surface elasticity. Even a relatively small (0.2 mol %) fraction of dodecanol in SDS may lead to a predominant content (up to 86 mol %) of dodecanol in the mixed adsorption layer. We applied the model for determining unknown contents of dodecanol in SDS samples at different stages of purification. The addition of NaCl may lead to a significant reduction in the mole fraction of dodecanol in the adsorption layer. The developed theoretical model and computational procedure are also appropriate for a quantitative analysis and computer modeling of the adsorption from other mixed ionic-nonionic surfactant solutions, at both air-water and oil-water interfaces.

The use of aqueous dispersed media, such as emulsio ns and miniemulsions, has many advantages ove... more The use of aqueous dispersed media, such as emulsio ns and miniemulsions, has many advantages over solution processes for chemical transformations and polymerization reactions, i.e. limited environment al impact, ease of products recovery and increased rea ction rate. Although, dispersed media are usually implemented from water/solvent mixtures, supercriti cal carbon dioxide (scCO 2) (Pc =74 bars; Tc = 31°C) constitutes an interesting alternative to the tradi ional organic solvents because it is inexpensive, non-toxic, nonflammable and environmentally friendlier. In this context, we develop a novel class of surfac e tive compounds able to stabilize water/scCO 2

(57)【要約】 非イオン型界面活性剤、ポリマーおよび以下の式Ｒ 1 Ｒ 2 Ｒ 3 ＮあるいはＲ 1 Ｒ 2 Ｒ 3 Ｎ + Ｘによる両性界面活性剤からなる液体洗浄用組成物が開示されている。 ... more (57)【要約】 非イオン型界面活性剤、ポリマーおよび以下の式Ｒ 1 Ｒ 2 Ｒ 3 ＮあるいはＲ 1 Ｒ 2 Ｒ 3 Ｎ + Ｘによる両性界面活性剤からなる液体洗浄用組成物が開示されている。 ここで置換基Ｒ 1 は６個から２２個の炭素原子を持つ、置換あるいは非置換、飽和あるいは不飽和、直鎖あるいは分岐鎖炭化水素鎖であり、ここで置換基Ｒ 2 およびＲ 3 はそれぞれ独立にＣ１からＣ６のアルキルカルボン酸基で、それらは同じあるいは違っていてもよく、そしてここでＸはＨである。 この組成物は改良された物理的安定性を示す利点がある。

ACS Symposium Series, 1983

The emergence of new flexible and wearable technologies should be performed with environmental an... more The emergence of new flexible and wearable technologies should be performed with environmental and safety considerations1. To meet these challenging aspects, this research focused on a new aqueous slurry formulation for the preparation of flexible and free-standing electrodes for Li-ion batteries. Carbon black, polyvinyl alcohol (PVA) and polyethylene glycol (PEG) were added to the active material. The anode material Li4Ti5O12 was chosen to develop this aqueous system thanks to it compatibility with aqueous process. The PVA/PEG ratio was optimized to obtain flexible and self-sustained electrodes after drying of the suspensions. The DSC (differential scanning calorimetry) measurements demonstrate the interaction between PVA and PEG polymers chains. SEM show good dispersion of all components within the electrodes. The PEG 6000 based electrodes displayed excellent electrochemical performances: up to 90% of the theoretical capacity at high current density (1C rate), which is comparable to the performances reported in the literature for flexible LTO electrode containing either CNTs or metallic current collector. Mild mechanical stress applied to the electrodes allowed to enhance the electrochemical performances. This could be related to the creation of tiny cracks leading to better penetration of the electrolyte in the electrode[2]. References 1- A.Vlad et al., Adv. Energy Mater. 2015, 5, 1402115 2- C. Piffet et al., Chem. Eng. J., 2020, 397, 125508Peer reviewe

Chemical Engineering Journal, 2020

processing of flexible, free-standing Li 4 Ti 5 O 12 electrodes for Li-ion batteries,

Polymer Bulletin, 1981

Halato-telechelic polymers (HTP) resulting from the neutralization of carboxy telechelic polymers... more Halato-telechelic polymers (HTP) resulting from the neutralization of carboxy telechelic polymers behave as useful ion-containing model compounds. Carboxy telechelic polybutadiene (Mn : 4,600) neutralized by magnesium methoxide exhibits a secondary relaxation mechanism characteristic of the ionic component. The activation process of this secondary relaxation obeys to an Arrhenius-type dependence and an activation energy of 30.5 Kcal/mole is calculated.

Journal of Colloid and Interface Science, 2001

The interaction of polyvinylpyrrolidone (PVP) with an anionic surfactant (sodium dodecyl sulfate,... more The interaction of polyvinylpyrrolidone (PVP) with an anionic surfactant (sodium dodecyl sulfate, SDS), a nonionic surfactant (pentaethylene glycol monodecyl ether, C 10 E 5), and a zwitterionic surfactant (lauryl amido propyl betaine, LAPB) has been investigated by means of pulsed gradient spin-echo NMR (FT-PGSE NMR), allowing self-diffusion coefficients to be determined. The results confirm the strong interaction prevailing in the PVP/SDS system, whereas no association has been observed in the PVP/C 10 E 5 and PVP/LAPB systems. Mixing PVP with two surfactants, namely SDS and C 10 E 5 or SDS and LAPB, results in the formation of ternary aggregates between the polymer and the mixed micelles.

Langmuir, 2000

Instability driven by diffusion flux across an asymmetric liquid film is theoretically investigat... more Instability driven by diffusion flux across an asymmetric liquid film is theoretically investigated. To specify the system, we consider an oil-water-air film; the transported species are oil molecules. The latter are dissolved (solubilized) at the oil-water interface, then they are transferred by diffusion across the aqueous film to the water-air interface, where they penetrate between the tails of adsorbed surfactant molecules. Fluctuational capillary waves at the two film surfaces are considered. The set of theoretical equations is solved to derive a dispersion relation between the wavenumber and the exponent of wave growth. The results reveal that if a local decrease in the film thickness appears, the water-air interface enters a zone enriched in dissolved oil. The newly adsorbed oil creates a surface tension gradient, which carries water away and causes a further decrease of the local film thickness in the concave zone, until eventually the film ruptures. The numerical results show that the film becomes less stable when its thickness decreases, its radius increases, and the diffusion flux across it is more intensive. Even very small decrements of the water-air surface tension, caused by the adsorbed oil, are sufficient to trigger the instability. Its appearance is not so sensitive to the degree of mobility of the oil-water interface. If the water-air surface is preequilibrated with the transported component (there is prespread oil), then the surface tension decrement and the instability disappear. The rupture of an asymmetric oil-water-air film is a precondition for entry of an oil drop at the water-air interface and effectuation of its foam-destructive action. Our results about a specific source of film instability could be helpful for a deeper understanding of the mechanisms of antifoaming.

Langmuir, 1997

We present experimental data showing that the surface tension, σ, of anionic surfactant (sodium d... more We present experimental data showing that the surface tension, σ, of anionic surfactant (sodium dodecyl dioxyethylene sulfate: SDP-2S) solutions undergoes a substantial change in the vicinity of the transition from sphere to cylinder in the micelle shape. The formation of cylindrical (rodlike) micelles at relatively low surfactant concentrations (between 2 and 8 mM) is promoted by the presence of Al 3+ ions in the solution. In the experiments we fixed the ionic strength of the added electrolyte but varied the molar fractions of NaCl and AlCl3. We established that the observed variation of σ in a vicinity of the sphereto-rod transition can be attributed to two competitive effects: (i) competition between Na + and Al 3+ counterions for the adsorption in the subsurface Stern layer and (ii) competition between the solution surface and the surfaces of the micelles to adsorb the Al 3+ counterions. The concentration of free Al 3+ ions in the solution is substantially reduced due to binding of Al 3+ to the micelles. The latter effect is studied experimentally by means of ultrafiltration experiments. We develop a theoretical model that allows us to calculate the true bulk (background) concentrations of Na + and Al 3+ ions, and the variation of σ in the vicinity of the sphere-to-rod transition. Good agreement between theory and experiment is achieved. The results show that the transition from sphere to cylinder in the micelle shape can be detected from the plot of the surface tension vs the surfactant-to-Al 3+ ratio. The paper also contains experimental data for the dependence of the CMC and surface tension of SDP-2S solutions on the ionic strength, which may represent independent interest.

Langmuir, 1997

The motion of the front between thick and thin foam film formed in a vertical frame is studied bo... more The motion of the front between thick and thin foam film formed in a vertical frame is studied both experimentally and theoretically. In the experiments we used sodium dodecyl sulfate solutions with added NaCl. The rate of motion of the front turns out to be constant for a given electrolyte concentration. Other important quantities that are measured are the thickness of the black film and the jump of the film tension, when the front reaches the bottom meniscus. The rate of the front turns out to be proportional to the jump of the film tension irrespective of the amount of added electrolyte. The theoretical model we developed allows quantitative interpretation of the experimental data. It is demonstrated that the motion of the front "thick-thin" film is accompanied with the formation of microscopic steady capillary waves in the transition zone. We show that the energy dissipation in the film is concentrated mainly into the latter part of the transition zone. The study can be helpful for the understanding of the mechanism of the foam films drainage as related to the stability of foams.

Langmuir, 1998

To study the electric properties of adsorption monolayers of an amphoteric surfactant, in our cas... more To study the electric properties of adsorption monolayers of an amphoteric surfactant, in our case lauryl dimethyl amine oxide (LDAO), we measured the-potential of latex particles covered with this surfactant. Its adsorption on the latex particles is estimated by dynamic surface tension measurements coupled with light scattering experiments. The influence of pH, ionic strength, and surfactant concentration on the electric properties of the adsorption monolayer has been examined. We propose a theoretical model which describes the dependence of-potential on both pH and the ionic strength. The model accounts for the adsorption of H + , Na + , and Clions on the amphoteric surfactant headgroups. Very good agreement between theory and experiment is achieved. The-potential measurements, coupled with the theoretical model, can be considered as a method for quantitative characterization of the ionization properties of amphoteric surfactants in adsorption layers. The latter properties are, in general, different from the surfactant ionization properties in the bulk of solution. We hope this approach can find application for characterizing various formulations used in the house hold and personal-care detergency, foaming, emulsification, etc.

Journal of Colloid and Interface Science, 1996

A theoretical approach to the kinetics of adsorption on the expanding interface of a micellar sur... more A theoretical approach to the kinetics of adsorption on the expanding interface of a micellar surfactant solution is proposed. For example, it can be the Langmuir adsorption isotherm The nonlinear partial differential equations of mass transfer of the micelles and monomers are reduced to ordinary differential equations, which are solved numerically along with the nonlin-c 10 (t) b Å G(t) G ϱ 0 G(t) , [1.2] earized adsorption isotherm as a boundary condition. Being more general, this theoretical approach is consistent also with the special case of small deviations from equilibrium widely used in the kinetwhere b and G ϱ are constants and t denotes time. Both nonics of micellization. The theory is applied further to fit the experiionic (3-5) and ionic (6) surfactants are found to comply mental data for dynamic surface tension of micellar solutions of with the Langmuir adsorption isotherm. More sophisticated sodium dodecyl sulfate and sodium polyoxyethylene-2 sulfate adsorption isotherms are also used (7). In some particular measured by the maximum bubble pressure (MBP) method. The cases (small adsorption, small deviations from equilibrium, expansion of the bubble surface is accounted for by using the etc.) the adsorption isotherm can be linearized and then stanexperimental dependence of the bubble size on time. The calcudard mathematical methods can be applied to solve the diffulated effective rate constant of micelle decay for sodium dodecyl sion problem, see e.g., Refs. (8-10). However, the general sulfate turns out to be sensitive to the mechanism of the micelle's boundary problem is essentially nonlinear. One way to solve disintegration. This provides a possibility for one to determine the it is to use perturbation series methods (11). Another aprate constants of the fast and slow processes in the relaxation kinetics of micellization by using a relatively simple experimental proach is to solve numerically the respective set of equations, technique for dynamic surface tension measurement like the MBP including the partial differential equation of diffusion (12, method.

Journal of Colloid and Interface Science, 1998

The great importance of foams in various fields of practice films and the decay of foams stabiliz... more The great importance of foams in various fields of practice films and the decay of foams stabilized with sodium dodecyl sulfate has stimulated studies of foam systems for many years (1). (SDS) is investigated. The ionic strength was kept constant, 0.024 The stability and the lifetime of foams are governed by the M, in all experiments. Sodium salts, Na 2 SO 4 , NaNO 3 , NaCl, Na 2 CO 3 , Na 3 PO 4 , and sodium citrate, as well as magnesium salts, properties of their structural units: thin liquid films (TLF) MgSO 4 , Mg(NO 3) 2 , MgCl 2 , and Mg(OOCCH 3) 2 , are used. The and Plateau borders (1-3). The latter are influenced by the lifetime and the critical thickness of rupture of the unstable films, rheological properties of the surfactant adsorption monoas well as the equilibrium thickness of the stable films, are mealayers and their interaction across the TLF. The electrostatic sured. The rate of drainage of the liquid from the foams and interaction, which gives rise to long-range double-layer their decay time are also measured. The influence of the bivalent forces (2) and to short-range hydration repulsion (4), plays counterion, Mg 2/ , is related to two major effects influencing the an important role in the stability of foam films. The effect film stability in the opposite directions: (i) increase of the surface of electrostatics was studied experimentally by variation of elasticity and viscosity due to connections between neighboring electrolyte concentration (2, 5, 6). Sharma and Khilar (7) surfactant headgroups produced by Mg 2/ and (ii) enhancement established that the addition of electrolyte affects the surface of the ionic correlation attraction between the film surfaces. The mobility. As a rule 1:1 electrolytes were used in these studdata show also an unexpectedly large influence of the co-ions on the film and foam stability. Carbonates, phosphates, and citrates ies. There are only few works on the effect of bivalent counhave the most significant stabilizing effect. At least two effects terions on the process of film thinning (8, 9). It was obmay be responsible for the larger stability of the films with co-ions served (9) that the type of film rupture depends to some of weak acids: (i) The dissolved carbonate and phosphate salts extent also on the type of co-ions. spontaneously adjust to pH 11.4 in the solution, which leads to The influence of co-ions (monovalent or bivalent) has hydrolysis of SDS to dodecanol. The latter increases the surface been studied mainly with respect to the properties of sodium elasticity, viscosity, and kinetic stability of films and foams. (ii) dodecyl sulfate (SDS) adsorption monolayers (10-12). Ya-The molecules of the carbonic, phosphoric, or citric acid can inmanaka (13) investigated the properties of vertical films and terconnect headgroups of neighboring SDS molecules in the surfoams containing sodium salts with various anions. These face adsorption monolayers by formation of multiple H-bonds. films and foams were stabilized by a nonionic surfactant Such a linking also enhances the kinetic stability. These hypotheses (polyoxyethylene nonylphenyl ether) instead of SDS. It was agree well with the accumulated experimental data and can be helpful for a better understanding of the role of citrates, phos-experimentally established that the stability of the studied phates, and other electrolytes in body-care and household defoams depends on the type of the anion in the solution. tergency.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999

We address the problem about the electro-diffusion-controlled adsorption from a submicellar solut... more We address the problem about the electro-diffusion-controlled adsorption from a submicellar solution of an ionic surfactant in the presence of a non-amphiphilic electrolyte (salt). We consider a disturbance of the surfactant adsorption layer, which is damped by the electro-diffusive transport of surfactant ions, counterions and coions. The evolution of the electric double layer with time is theoretically examined. The counterion adsorption (binding) is taken into account. Our purpose is to find the long-time asymptotic solution of the full electro-diffusion boundary problem. Assuming small perturbations the problem is linearized and a set of three differential operator equations is obtained. In the asymptotic case of long times these differential equations reduce to hypergeometric equations, whose solutions, fortunately, can be expressed in terms of elementary functions. As a result, explicit expressions for the characteristic relaxation times of the adsorptions of surfactant ions and counterions are obtained. Next we determine the characteristic relaxation time of surface tension, which is different from the adsorption relaxation time because of a specific contribution from the dynamic diffuse electric double layer. The thermodynamic parameters, entering the formula for the relaxation time, are expressed for various surfactant adsorption isotherms, those of Henry, Langmuir, Freundlich, Frumkin and van der Waals. The theory gives a quantitative interpretation of the experimental finding that the addition of salt accelerates the relaxation of the surface tension for the higher surfactant concentrations, but decelerates it for the lower surfactant concentrations. The results could be also useful for a theoretical interpretation of the processes in foams and emulsions under dynamic conditions.

Colloid and Polymer Science, 2003

Langmuir, 2003

The main target of this study is to develop a theoretical method for determining small contents o... more The main target of this study is to develop a theoretical method for determining small contents of dodecanol in samples of sodium dodecyl sulfate (SDS) by a detailed analysis of surface-tension isotherms. As a tool for our analysis, we employ the van der Waals model. Its application to data for alkanols and anionic surfactants gives an excluded area per adsorbed molecule equal to the geometrical area of the molecular cross section and adsorption energies consonant with Traube's rule. Because the dodecanol and SDS have different excluded areas, we extended the van der Waals model for the case of a two-component adsorption layer, with account for the counterion binding in the Stern layer. General expressions for the surface free energy, two-dimensional equation of state, surface chemical potentials, adsorption isotherms, and surface dilatational elasticity are derived. The experimental surface-tension isotherms are fitted by varying only one adjustable parameter. The model was successfully tested against data for solutions of SDS with a known content of dodecanol. Knowing the parameters of the model, we computed various properties of the surfactant adsorption layer. The results show that the presence of a small amount of dodecanol leads to a considerable increase of the total adsorption and surface elasticity. Even a relatively small (0.2 mol %) fraction of dodecanol in SDS may lead to a predominant content (up to 86 mol %) of dodecanol in the mixed adsorption layer. We applied the model for determining unknown contents of dodecanol in SDS samples at different stages of purification. The addition of NaCl may lead to a significant reduction in the mole fraction of dodecanol in the adsorption layer. The developed theoretical model and computational procedure are also appropriate for a quantitative analysis and computer modeling of the adsorption from other mixed ionic-nonionic surfactant solutions, at both air-water and oil-water interfaces.

The use of aqueous dispersed media, such as emulsio ns and miniemulsions, has many advantages ove... more The use of aqueous dispersed media, such as emulsio ns and miniemulsions, has many advantages over solution processes for chemical transformations and polymerization reactions, i.e. limited environment al impact, ease of products recovery and increased rea ction rate. Although, dispersed media are usually implemented from water/solvent mixtures, supercriti cal carbon dioxide (scCO 2) (Pc =74 bars; Tc = 31°C) constitutes an interesting alternative to the tradi ional organic solvents because it is inexpensive, non-toxic, nonflammable and environmentally friendlier. In this context, we develop a novel class of surfac e tive compounds able to stabilize water/scCO 2

(57)【要約】 非イオン型界面活性剤、ポリマーおよび以下の式Ｒ 1 Ｒ 2 Ｒ 3 ＮあるいはＲ 1 Ｒ 2 Ｒ 3 Ｎ + Ｘによる両性界面活性剤からなる液体洗浄用組成物が開示されている。 ... more (57)【要約】 非イオン型界面活性剤、ポリマーおよび以下の式Ｒ 1 Ｒ 2 Ｒ 3 ＮあるいはＲ 1 Ｒ 2 Ｒ 3 Ｎ + Ｘによる両性界面活性剤からなる液体洗浄用組成物が開示されている。 ここで置換基Ｒ 1 は６個から２２個の炭素原子を持つ、置換あるいは非置換、飽和あるいは不飽和、直鎖あるいは分岐鎖炭化水素鎖であり、ここで置換基Ｒ 2 およびＲ 3 はそれぞれ独立にＣ１からＣ６のアルキルカルボン酸基で、それらは同じあるいは違っていてもよく、そしてここでＸはＨである。 この組成物は改良された物理的安定性を示す利点がある。

ACS Symposium Series, 1983