Dodecyltrimethylammonium Bromide Solutions Research Articles

Dynamic Interfacial Properties and Foamability of DoTAB/SiO2 Mixtures

The interaction between nanoparticles and cationic surfactants is an exciting and emerging field in interfacial science. This area of research holds significant promise, linking fundamental principles to practical applications in a variety of industries, including chemical processes, biomedical applications and the petroleum industry. This study explores the interaction between dodecyltrimethylammonium bromide (DoTAB) and silica (SiO2) nanoparticles, investigating their influence on dynamic interfacial properties and foam characteristics. Through equilibrium and dynamic surface tension measurements, along with examining the dilational visco-elasticity behavior, this research reveals the complex surface behavior of DoTAB/SiO2 mixtures compared to individual surfactant solutions. The foamability and stability experiments indicate that the addition of SiO2 significantly improves the foam stability. Notably, stable foams are achieved at low SiO2 concentrations, suggesting a cost-effective approach to enhancing the foam stability. This study identifies the optimal stability conditions for 12 mM DoTAB solutions, emphasizing the crucial role of the critical aggregation concentration region. These findings offer valuable insights for designing surfactant-nanoparticle formulations to enhance foam performance in various industrial applications.

Effects of static magnetic field on the surface tension of surfactant solutions

AbstractThe magnetic field (MF) effects resulting from water or solution treatments are still of significant interest. However, a relatively small number of papers have been published dealing with the pure surfactant solutions alone. On the other hand, surfactants are applied in many industrial processes as well as in everyday life and are also present in different waste waters. Therefore, it seemed interesting to investigate whether some effects would appear after the MF treatment of pure aqueous surfactant solutions. In the earlier published papers after MF action the changes in water evaporation rate and the surface tension were found for both the cationic dodecyltrimethylammonium bromide (DTAB) and anionic sodium dodecyl sulfate (SDS) solutions. The gradient MF originated from three connected ring magnets inside which the solutions were placed. The objective of this paper is to study whether using the same magnets but in a different position the effects of the MF are observed. The given surfactant solution in a closed vessel was placed in an uniform MF when the magnets were in the “lying” position. The investigated solutions on the magnet surface remained for 24 h. In this paper, despite SDS and DTAB also the cationic hexadecyltrimethylammonium bromide (CTAB) and nonionic Triton X‐100 solutions were applied. It appeared that in the uniform MF the surface tension of cationic and anionic surfactant solutions changes. However, larger changes were observed in the gradient MF. Generally, the changes of surface tension depend on the surfactant kind and its concentration. Stronger MF influence was found for the cationic surfactant and almost no changes were observed for nonionic Triton X‐100.

Oscillations in Dynamic Surface Tension of Cationic-nonionic Binary Surfactant Aqueous Solutions.

In this work, the adsorption dynamics of mixed aqueous solutions of tetraethyleneglycol monoocthyl ether (C8E4) - dodecyltrimethylammonium bromide (DTAB) were studied using sessile bubble surface tensiometry. When C8E4 was added to the DTAB solution, the dynamic surface tension exhibited a unique oscillation decay pattern. In contrast, the addition of DTAB to the C8E4 solution resulted in a simple monotonic decay of the surface tension. The same trend was observed for mixtures of tetradecyltrimethylammonium bromide (TTAB) and DTAB. The occurrence of two distinguishable dynamic surface tension behaviors showed reasonable similarity with the theory of the adsorption kinetics of polymer solutions, where the surface tension oscillation was caused by the delayed desorption of polymers due to the conformational change at the solution surface. We compared the dynamic surface tension of binary surfactant systems and the polymer solution theory, and discussed the origin of surface tension oscillations based on the difference in the surface activity of the surfactants.

On the determination of critical micelle concentration of partially dissociated ionic surfactants using contact angle data

The contact angle (CA) data has been utilized for determining the critical micelle concentration (cmc) of fully dissociated surfactant SDS, but not for nonionic surfactants Triton X-100 and C12E6 [Thu et al., J.Mol.Liq (2019) 111582]. Could this approach work for a partially dissociated ionic surfactant such as dodecyltrimethylammonium bromide (DTAB)? To verify this, this work studied the evaporation process of DTAB(aq) solution drops on parafilm. The relaxations of CA, wetting diameter, and drop volume were recorded during evaporation to determine the advancing/receding (θa and θr) CA’s. The data revealed that the breakpoints of θa and θr matched well with the cmc from the ST data; thereby, confirming that the aforementioned approach is viable for a partially dissociated ionic surfactant. Additional examination of the relaxation data and drop profiles revealed that the movement of a solution drop’s triple line (pinning-depinning behavior) during the evaporation process is primarily dependent on the localized surface morphology.

Gemini surfactant behavior of conventional surfactant dodecyltrimethylammonium bromide with anionic azo dye Sunset Yellow in aqueous solutions

• DTMABr may exhibit a gemini surfactant behavior in surfactant-dye solutions. • Surfactant/dye interactions have a role in exhibiting this behavior of DTMABr. • H-/J-aggregations of Sunset Yellow depends on its concentration in DTMABr solution. In this study, the interaction of an anionic azo dye Sunset Yellow with conventional cationic surfactant dodecyltrimethylammonium bromide (DTMABr) has been examined as a function of the dye concentration at 25 °C by electrical conductivity and UV–VIS spectroscopy measurements. Carpena’s method, combined with Aguiar’s approach, was applied to the analysis of the conductivity data for evaluating the micellization parameters such as critical micelle concentrations (cmc), degree of counterion bindings (β), and micellization Gibbs free energies (Δ mic G) from the specific conductivity-surfactant concentration curves. The UV–VIS absorption spectroscopy measurements were performed to obtain information on the dye concentration dependence of the stacking properties of Sunset Yellow in water. The results indicated that although DTMABr is a conventional surfactant with a single alkyl chain, it shows gemini surfactant behavior at relatively high dye concentrations as a result of the surfactant-dye interactions. To the best of our knowledge, this is the first study that shows both the gemini surfactant behavior of DTMABr in the presence of SSY and J-aggregations of SSY at high SSY concentrations in the presence of DTMABr. Furthermore, in the presence of DTMABr, the SSY molecules at low concentrations form H-aggregates; they show J-aggregation at high concentrations.

Adsorption behaviors and emission properties of p-sulfonatocalixarene/ammonium-based surfactant systems: A comparison between the effects of gemini surfactant and its corresponding monomeric surfactant

So far, the research on calixarene/surfactant systems has been mainly focused on their aggregation characteristics due to their potential applications as stimuli-responsive systems, while the reports about their absorption behavior and spectroscopic properties have been limited. Understanding basic properties of supra-amphiphilic molecules is of great significance to improve their application performance and expand their application potential. In the present study, the interactions of p-sulfonatocalix[n]arenes (SC[n], n = 4, 6 and 8) with the cationic surfactants (including dodecyltrimethyl ammonium bromide (DTAB), pentamethylene-1,5-bis (dimethyldodecyl ammonium bromide) (12-5-12), and octamethylene-1,8-bis(dimethyldodecyl ammonium bromide (12-8-12)) were studied by measuring surface tension, fluorescence spectra and 1H NMR spectra. It was found that SC[n] changed the absorption behaviors of 12-s-12 (s = 5 and 8) and DTAB at air/water surface in different ways. In the presence of SC[n], the value of γ for 12-s-12 remains almost constant until 12-s-12 content reaches C1, then decreases sharply until C2, followed by a slow decrease up to the CMC. The surface tension of DTAB/SC[n] solution begins to decrease at a very low concentration of DTAB until Ca, followed by a short plateau until Cb, and then, the surface tension increases sharply until Cc, after which, the surface tension curve gradually overlaps with that of single DTAB solution. Meanwhile, the binding of SC[n] with these surfactants makes SC[n] emit fluorescence, and the quantum yields for SC[n]/12-s-12 systems are higher than those for SC[n]/DTAB systems. Supra-amphiphiles have been expected as smart materials. This study may provide meaningful information for application of calixarene-based supra-amphiphiles.

Nucleation of Surfactant-Alkane Mixed Solid Monolayer and Bilayer Domains at the Air-Water Interface.

We investigated the wetting transitions of tetradecane and hexadecane droplets in dodecyltrimethylammonium bromide (C12TAB), tetradecyltrimethylammonium bromide (C14TAB), and hexadecyltrimethylammonium bromide (C16TAB) aqueous solutions. By varying the surfactant concentration, the formation of mixed monolayers of a surfactant and an alkane was observed at the air–water interface. Depending on the combination of surfactant and alkane, these wetting monolayers underwent another thermal phase transition upon cooling either to a frozen mixed monolayer (S1) or a bilayer structure composed of a solid monolayer of a pure alkane rested on a liquid-like mixed monolayer (S2). Based on the phase diagrams determined by phase modulation ellipsometry, the difference in the morphology of the nucleated S1 and S2 phase domains was also investigated using Brewster angle microscopy. Domains of the S1 phase were relatively small and highly branched, whereas those of the S2 phase were large and circular. The difference in domain morphology was explained by the competition of the domain line tension and electrostatic dipole interactions between surfactant molecules in the domains.

Magnetic Field Effects on Aqueous Anionic and Cationic Surfactant Solutions Part II: Surface Tension

Magnetic Field (MF) effects on water and dispersed systems have been studied for more than half of century. However, so far there is no complete understanding of the observed changes in the properties of studied systems if it is solely based on the classical theories of magnetic field action. In Part I of this paper we presented results of MF influence on the evaporation rate of aqueous solutions of anionic surfactant Sodium Dodecyl Sulphate (SDS) and cationic one Dodecyl Trimethylammonium Bromide (DoTAB). In this paper static magnetic field effects on the surface tension of the above-mentioned surfactants are presented. The concentrations of the solutions used were both below and above their Critical Micelle Concentration (CMC). The solutions were under the MF action for 60 min in a closed vessel and were stirred by hand every 15 min. Previously it was found that the surface tension of pure water (distilled in a quartz apparatus) decreased by 2.1 mN/m after similar the MF treatment. Moreover, the memory effect lasted longer than 60 min. In case of the surfactant solutions the surface tension changed depending both on the kind of surfactant and its concentration. Bigger changes were observed for cationic DoTAB. In the solutions below their CMC the surface tension was lower after MF treatment. However, the surface tension of DoTAB solution at CMC increased several mN/m after the MF treatment. In the solutions concentrated above the CMC, respectively, the MF effects were practically vanishing. The observed changes are discussed in detail considering the structure of the surfactant adsorbed layers and acceleration force acting on the ions which was calculated from the Lorentz equation. To our knowledge, such results are published in the literature for the first time and they should be considered as preliminary ones. More systematic experiments are needed to better understand the observed changes.

In situ modification of polyamide reverse osmosis membrane module for improved fouling resistance

In situ improvement of fouling resistance of the state-of-the-art polyamide reverse osmosis membrane module on the basis of the fouling characteristic of the fluid to be treated is of great practical significance. In this work, in situ modification was performed with the spiral wound polyamide reverse osmosis membrane module for improved fouling resistance to specific foulant. Small molecular monomers of amidosulfonic acid (ASA), diethanolamine (DEA) and piperazine (PIP) were grafted onto the surface of the flat-sheet polyamide-based thin-film composite membrane within the module separately through 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-activated amidation of carboxyl groups. The results of fouling experiments indicated that the fouling resistance of the polyamide reverse osmosis membrane module to the model foulants of bovine serum protein (BSA), sodium alginate (SA) and dodecyl trimethyl ammonium bromide (DTAB) could be effectively improved through grafting monomers ASA, DEA and PIP, respectively, showing significant reduction in declines of membrane flux to aqueous BSA, SA and DTAB solutions by 47.2%, 41.3% and 34.4%. The changes of membrane surface hydrophilicity and negative charge were in charge of the improved antifouling property. The in-situ modification was also found to slightly enhance membrane salt rejection and have nearly no influence on membrane water flux.

An investigation into surfactant flooding and alkaline-surfactant-polymer flooding for enhancing oil recovery from carbonate reservoirs: Experimental study and simulation

ABSTRACTThe main aim of the present work was to study history matching of surfactant flooding using CMG-STARS simulator and experimental results. In the experimental case, the critical micellar concentration of dodecyltrimethylammonium bromide solution is obtained, and the changes in the contact angle are investigated from 1 to 10% weight. Then, after water flooding, surfactant flooding is applied on the critical micellar concentration of dodecyltrimethylammonium bromide. In the simulation case, after history matching of production data, the performance of alkaline-surfactant-polymer flooding using sodium hydroxide, hydrolyzed polyacrylamide, and that surfactant was a prediction. The numerical simulation alkaline-surfactant-polymer flooding increased the oil recovery factor 26% more than surfactant flooding.

The Effect of a Background Electrolyte on the Viscosity of Aqueous Dodecyltrimethylammonium Bromide Solutions

Conductometry and viscometry have been employed to study the effect of a background electrolyte (KBr) taken in concentrations of 0.03 and 0.1 M on the critical micelle concentration of dodecyltrimethylammonium bromide (С12ТАB) and the dependence of relative viscosity η/η0 of С12ТАB micellar solutions on the overall surfactant concentration. It has been found that, as a first approximation, each of these dependences may be represented as the sum of two linear portions. Concentrations c* of С12ТАB micellar solutions, which correspond to the inflections between the two linear portions in the concentration curves of relative viscosity, have been determined. The Einstein equation η/η0 = 1 + 2.5p (p is the volume fraction of the dispersed phase and 2.5 is a theoretical parameter that takes into account the spherical shape of the particles) has been transformed into a form corresponding to the concentration dependence of the relative viscosity on the overall surfactant concentration to make it applicable to the consideration of low-concentration systems, which are uncomplicated by intermicellar interaction. In particular, the applicability of the above equation for estimating micelle radii has been studied. It has been shown that the (η/η0–1) = f(c/с01–1) concentration dependences represented in bilogarithmic coordinates (c is the overall С12ТАB concentration and c01 is the critical micelle concentration) are linear in the absence of a significant intermicellar interaction and have slopes equal to unity. This fact may be considered as a criterion for the applicability of the Einstein equation to micellar solutions.

Comparison of Anionic, Cationic and Nonionic Surfactants as Dispersing Agents for Graphene Based on the Fluorescence of Riboflavin.

Fluorescence quenching is a valuable tool to gain insight about dynamic changes of fluorophores in complex systems. Graphene (G), a single-layered 2D nanomaterial with unique properties, was dispersed in surfactant aqueous solutions of different nature: non-ionic polyoxyethylene-23-lauryl ether (Brij L23), anionic sodium dodecylsulphate (SDS), and cationic hexadecyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB). The influence of the surfactant type, chain length and concentration, G total concentration and G/surfactant weight ratio on the fluorescence intensity of vitamin B2 (riboflavin) was investigated. The quality of the different G dispersions was assessed by scanning and transmission electron microscopies (SEM and TEM). A quenching phenomenon of the fluorescence of riboflavin was found for G dispersions in all the surfactants, which generally becomes stronger with increasing G/surfactant weight ratio. For dispersions in the ionic surfactants, the quenching is more pronounced as the surfactant concentration raises, whilst the non-ionic one remains merely unchanged for the different G/Brij L23 weight ratios. More importantly, results indicate that DTAB solutions are the optimum media for dispersing G sheets, leading to an up to 16-fold drop in the fluorescence intensity. Understanding the mechanism in fluorescence quenching of G dispersions in surfactants could be useful for several optical applications.

Enhanced Catalytic Activity of α-Chymotrypsin in Cationic Surfactant Solutions: The Component Specificity Revisited.

Enhanced catalytic activity (super activity) of enzymes in the presence of surfactants is of key importance in "micellar enzymology"; such super activity is not very trivial, it is highly system specific, and the mechanism behind the activity enhancement is not always well apprehended. We report the catalytic activity of α-chymotrypsin (CHT) on ala-ala-phe-7-amido-4-methylcoumarin (AMC) in the presence of cationic surfactants of different hydrophobic chain lengths: dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) and octadecyltrimethylammonium bromide (OTAB). It is observed that in comparison to buffer the catalytic activity of CHT is enhanced 5-fold in premicellar DTAB solutions, while negligible changes are observed in CTAB and OTAB. Activity decreases considerably in the post micellar concentration, specifically for the latter two surfactants. A similar trend is also obtained in another substrate 2-napthyal acetate hydrolysis. Such surfactant specific superactivity is intriguing. The protein's secondary and tertiary structures in the presence of these surfactants are determined using circular dichroism (CD) spectroscopy and it is found that both CTAB and OTAB perturb the protein structure significantly, especially in the post micellar concentrations. DTAB, on the other hand, does not produce noticeable changes in the protein structure. The various pairwise interactions present in the system have been underlined using both steady-state and time-resolved fluorescence spectroscopy. Assuming a three-step kinetics model, we determine the free energy changes of the reaction, and the observations have been discussed in the light of the various interactions among the components.

Cationic and anionic surfactants interaction in water and methanol–water mixed solvent media

The micellar properties between dodecyltrimethylammonium bromide (DTAB) and sodium dodecylsulfate (SDS) in water and 0.10, 0.20, and 0.30 volume fractions of methanol in methanol–water mixed solvent media have been studied by conductivity and surface tension measurements at 293.15 K. The concentration of dodecyltrimethylammonium bromide varied from 0.0001 to 0.03 mol·L− 1 in the presence of ~ 0.01 mol·L− 1 sodium dodecylsulfate and the concentration of sodium dodecylsulfate varied from 0.001 to 0.015 mol·L− 1 in the presence of ~ 0.005 mol·L− 1 dodecyltrimethylammonium bromide. Hence, the concentrations of cationic rich (DTAB–SDS) and anionic rich (SDS–DTAB) solutions have been taken in the ratio of 3:1. The critical micelle concentrations (cmc) of DTAB–SDS and SDS–DTAB solutions have been determined by conductivity and surface tension measurements at 293.15 K. The physicochemical properties such as Gibb's free energy of micellization (ΔGmo), free energy of surfactant tail transfer (ΔGtranso), maximum surface excess concentration (Гmax), area occupied by surfactant molecule (Amin), surface pressure at the cmc (πcmc), packing parameters (P) and standard free energy interfacial adsorption (ΔGadso) are calculated in water, 0.10, 0.20 and 0.30 volume fractions of methanol–water at 293.15 K. Addition of methanol significantly affects the physicochemical properties between DTAB and SDS. With increasing concentration of methanol, the cohesive force and the dielectric constant decrease that affects the micellization and other physicochemical properties. The micellization between DTAB and SDS have been assessed in terms of different solvent parameters. The ratio of the solvent surface tension to the limiting surface tension at the cmc has been used as the solvophobic effect.

Effect of Methanol on Viscosity of Aqueous Solutions of Cationic Surfactants at 298.15 to 323.15 K

Viscosity measurements have been made to the solutions of dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB) in 0.10, 0.20, 0.30, and 0.40 volume fractions of methanol in methanol-water mixed solvent media at 298.15, 308.15, 318.15, and 323.25 K. Critical micelle concentration (CMC) values have been determined. From relative viscosity for surfactant solutions, related viscosityBcoefficients are calculated and the values are interpreted in terms of solute-solvent interactions.

Thermodynamic and aggregation properties of aqueous dodecyltrimethylammonium bromide in the presence of hydrophilic ionic liquid 1,2-dimethyl-3-octylimidazolium chloride

The effect of a trisubstituted imidazolium based hydrophilic ionic liquid (IL), 1,2-dimethyl-3-octylimidazolium chloride [odmim][Cl] on the thermodynamic and aggregation properties of dodecyltrimethylammonium bromide (DTAB) at temperatures 298.15–318.15K has been studied by conductivity measurements in aqueous media. From the temperature dependence of critical micelle concentration (cmc), various thermodynamic parameters of micellization viz. standard free energy change (ΔGm°), standard enthalpy change (ΔHm°) and standard entropy change (ΔSm°) have been evaluated. Further fluorescence probe analysis has been utilized to obtain cmc value in order to validate the cmc values obtained from conductivity measurements. The micelles formed just like in aqueous medium and cmc values were found to be changing at different wt% of IL than in water. The cmc value of aqueous DTAB solution decreases until 2.0wt% of IL in the medium. The properties of aqueous DTAB solution change in a different way at higher concentration of IL. The variation in chemical shifts of surfactant protons in the presence of IL revealed that the electrostatic interactions have a prominent influence on the DTAB micellization in IL/water systems. It is shown that the modification in aggregation properties of DTAB is related to the lipophilicity of interacting ions.

Influence of Sodium Salts on the Micellization and Interfacial Behavior of Cationic Surfactant Dodecyltrimethylammonium Bromide in Aqueous Solution

Micellar and surface properties of aqueous dodecyltrimethylammonium bromide (DTAB) solutions have been studied in the absence and presence of several sodium salts including NaCl, NaH2PO4, Na2HPO4, Na2CO3, Na2SO4, Na3PO4, and Na3Cit. The values of critical micelle concentration (cmc), degree of anionic binding (β), surface tension at the cmc (γcmc), adsorption efficiency (pC20), effectiveness of surface tension reduction (Πcmc), maximum surface excess concentration (Γmax), minimum surface area per molecule (Amin) at interface of air–liquid, standard Gibbs free energy of micellization (ΔmicG°), and adsorption at air/water interfaces (ΔGad°) were evaluated from the conductivity and surface tension measurements at 298.15 K. The results show that all salts effectively reduce the cmc values of the cationic surfactant DTAB. The ability of the anions to promote the micellization of DTAB decreases in the order of Cit3– > PO43– > SO42– > CO32– > HPO42– > Cl– > H2PO4–. The effect of anions of the added salts on the ...

Modulating effect of ionic liquid 1-butyl-2,3-dimethylimidazolium chloride on micellization behaviour of cationic surfactant dodecyltrimethylammonium bromide in aqueous media

The micellization behaviour of cationic surfactant dodecyltrimethylammonium bromide (DTAB) has been studied upon addition of 1-butyl-2,3-dimethylimidazolium chloride, [bdmim][Cl], a trisubstituted imidazolium based ionic liquid (IL) in aqueous media. The critical micelle concentration (cmc) and degree of dissociation (α) for the micelles were determined from conductance measurements for a temperature range of 298.15–318.15K at different wt% of IL in the medium. The thermodynamic parameters (ΔGm°, ΔHm° and ΔSm°) of micellization were evaluated by applying the charged pseudo-phase separation model for the micellar systems. Further fluorescence probe analysis has been utilized to obtain cmc value as a complementary to conductivity in order to validate the cmc values obtained from conductivity measurements. A continuous decrease in cmc was observed with addition of 10.0wt% of IL but further addition of IL causes an increase in cmc of the surfactant solution. The aggregation number, Nagg and size of aggregates in aqueous DTAB solutions at different wt% of IL were determined by fluorescence quenching of pyrene and dynamic light scattering (DLS) studies, respectively. 1H NMR measurements of post-micellar solution at lower wt% of IL have been done to understand the different inter-molecular interactions of surfactant molecules with [bdmim][Cl].

Corrosion resistance evaluation of Ni‐P\nano‐ZrO2 composite coatings by electrochemical impedance spectroscopy and machine vision method

Ni‐P\nano‐ZrO2 composite coatings were obtained on the AISI 304 steel substrate by the electroless method from a bath containing dodecyltrimethylammonium bromide (DTAB). This cationic surfactant prevents ZrO2 agglomeration in the bath and affects the ZrO2 content in the coating, hence it alters functional properties of the coatings. It has been found in this study that corrosion resistance of the composite coatings depends on the surfactant concentration in the bath. The estimation of corrosion resistance was carried out by electrochemical impedance spectroscopy. The degree of the sample surface coverage with corrosion products was determined by the machine vision method. The coating obtained from the 0.88 g/dm3 DTAB solution showed the best protective properties. The machine vision method was shown to be an effective complementary tool to evaluate protective properties of the coatings.

Study of Aqueous Solutions of Surfactants in the Presence of Alcohols by Means of Ultrasonic Relaxation

Abstract Ultrasonic absorption coefficients in aqueous solutions of surfactants, octyltrimethylammonium bromide, dodecyltrimethylammonium bromide, and tetradecyltrimethylammonium bromide have been measured in the presence of 2-propanol or ethanol in the frequency range from 0.8 to 220 MHz at 25 °C. The frequency dependence of the observed absorption in solution of octyltrimethylammonium bromide has been characterized by a Debye-type relaxation equation with one single relaxation frequency which decreases with the surfactant concentration. On the other hand, the dependences in solutions of dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide have been well fitted to the equation with two relaxation frequencies. One relaxation frequency decreases with the surfactant concentrations, and the other relaxation frequency shows concentration independence trend. The relaxation mechanisms have been considered on the basis of interaction between surfactant monomer and alcohol aggregate and of a conformational change of the surfactants with long hydrophobic groups to which plural alcohol molecules (dumpling cake) attract. The rate and thermodynamic parameters have been determined for aqueous solutions of octyltrimethylammonium bromide coexisting with 2.00 mol dm−3 2-propanol and 3.00 mol dm−3 ethanol. It has been speculated from the analysis that the dumpling cake of alcohols attaches and detaches on and from the alkyl chains of the surfactants. The number of alcohols in the aggregate is dependent on size of alcohol molecule although the forward and backward rate constants are not very dependent on coexisting alcohols. However, only the orders of the rate constants for the systems of dodecyltrimethylammonium bromide solution with 2.00 mol dm−3 2-propanol have been speculated because of too many parameters which should be determined. Following the proposed reaction model, the relation between the surfactant concentration dependence of adiabatic compressibility and the solution characteristics has been discussed.