Mixed Micellization and Interfacial Properties of Ionic Liquid‐Type Imidazolium Gemini Surfactant with Amphiphilic Drug Amitriptyline Hydrochloride and its Thermodynamics

The thermodynamics of mixed micellization of amitriptyline hydrochloride (AMT) with ionic liquid‐type imidazolium gemini surfactant ([C₁₀‐4‐C₁₀im] Br₂), was investigated at different mole fractions and temperatures by surface tension measurements. The deviation of the critical micelle concentration (CMC) from the ideal critical micelle concentration (CMC * ), micellar mole fraction () from ideal micellar mole fraction (), the values of interaction parameter () and activity coefficients () (for both mixed micelles and mixed monolayer) explained the non‐ideal behavior (i.e., synergistic behavior) of binary mixtures. The excess free energy (?G_ex) for the AMT‐[C₁₀‐4‐C₁₀im] Br₂ binary mixtures explained the mixed micelles stability in comparison to micelles of [C₁₀‐4‐C₁₀im] Br₂ and pure AMT. Interfacial parameters, i.e., Gibbs surface excess (), minimum head group area at air/water interface (), free energy of micellization (), and standard Gibbs energy of adsorption (?G_ads^o) were also evaluated for the systems. The standard entropy of adsorption (?S_ads^o) was found higher than the standard entropy of micellization (?S_m^o) at all mole fractions of AMT (α₁).     

Synthesis and Micellization of Organosilicon Gemini Quaternary Ammonium Surfactants

A novel class of organosilicon gemini quaternary ammonium surfactant alkyl‐α, ω‐bis(diethyl‐methyl‐dimethoxy‐silopropyl ammonium bromide) (α, ω = 1,4; 1,6; 1,8) was synthesized and characterized by ¹H‐nuclear magnetic resonance (NMR) and elemental analysis. It is found that the quaternization reaction has two steps: first single quaternization and then double quaternization. The effect of solvent on convert ratio has the following sequence: polar aprotic solvents > polar protic solvents > aromatic solvents. The electrical conductivity of aqueous solution was measured at 20, 25, 30 and 35 °C, and the thermodynamic properties of , and were calculated according to the mass action model and Gibbs equation. It is shown that the enthalpy driven and entropy driven are almost equal in the micellization of [SiC₃‐4‐SiC₃]Br₂ and [SiC₃‐6‐SiC₃]Br₂, but in the micellization of [SiC₃‐8‐SiC₃]Br₂, the enthalpic contribution becomes significant and the effect of thermal is greater than the degree of order in the micellization.     

Imidazolium‐Based Ionic Liquid as Modulator of Physicochemical Properties of Cationic,Anionic, Nonionic,and Gemini Surfactants

The aggregation morphology of 2 cationic surfactants (cetyldimethylethanolammonium bromide and cetyldiethylethanolammonium bromide), an anionic surfactant (sodium dodecylbenzenesulfonate), a nonionic surfactant (Triton X‐100), and 2 gemini surfactants (16‐4‐16,2Br^?[butanediyi‐1,4‐bis(dimethyldohexylammonium bromide)] and 16‐6‐16,2Br^?[hexanediyi‐1,6‐bis(dimethyldohexylammonium bromide)]) in the presence of the ionic liquid (IL) 1‐ethyl‐3‐methylimidazoliumbromide [Emim][Br] is studied using various techniques such as surface tension, conductivity, and UV–visible and fluorescence spectroscopy. Increasing the concentration of [Emim][Br] results in a decrease in the critical micelle concentration (CMC) value of the surfactants. Various interfacial properties, namely the surface excess concentration (Г_max), minimum area per molecule at the air–water interface (A_min)_, and surface pressure at the CMC (π_cmc), as well as the thermodynamic parameters such as free energy of the given air/water interface (), Gibbs free energy of micelle formation (), Gibbs free energy of micellization per alkyl tail (), Gibbs energy of transfer (), and standard free energy of adsorption () were also investigated. The aggregation number (N_agg) was determined by the fluorescence method. It was observed that N_agg decreased with increasing weight‐percent of the IL.     

Synthesis and Investigation of Surface Active Properties of Counterion Coupled Gemini Surfactants

Three counterion coupled gemini (cocogem) surfactants in the series 1,6‐bis(N,N‐alkyldimethylammonium) adipate, referred as n‐6‐n (n = 12, 14, 16), were synthesized, purified and characterized by ¹H NMR and ¹³C NMR. Their physicochemical properties were investigated by electrical conductivity and surface tension measurements. The degree of ionization, critical micelle concentration (CMC), surface excess at the air/solution interface (Γ_max), minimum area per surfactant molecule at the air/solution interface (A_min), surface tension at the CMC (γ_CMC), and pC₂₀ (negative log of the surfactant molar concentration, required to reduce the surface tension of water by 20 mN m^?1) were calculated. Increase in tail length of the surfactants increases the efficiency of surfactants to decrease the surface tension of water. Thermodynamic parameters, viz. molar free energy at the maximum adsorption attained at CMC (G_min), standard Gibb's energy of micellization (), and standard Gibbs energy of adsorption (), were also calculated. The and values show that the monomers were preferred to be adsorbed at the air/water interface and then in the micellar formation in the bulk. Additionally, fluorescence measurements were used to find the aggregation number. Other relevant surface properties (Krafft point, emulsion stability, foaming ability, micellar stability and dye solubilization ability) were also evaluated. These results suggest that with respect to emulsion formation, micellar stability and dye solubilization, the cocogem with a 16‐carbon chain gives better results, producing 89 % more stable foams and shows better aggregational behavior.     

Counterion-Induced Cationic Flexible Nanoparticle Catalytic of Piperidinolysis of Phenyl Salicylate

The removal of PSa^? from bulk aqueous phase to the pseudo‐micellar phase by halobenzoate counterion X is responsible for the monotonic increase in k_obs (pseudo first‐order rate constants) with the increase in the values of [MX] where MX = sodium salts of 2‐, and 4‐halobenzoic acids. The values of ion exchange constants, or for X = 2‐ and 4‐halobenzoate ions in the presence of tetradecyltrimethylammonium bromide (TTABr) were calculated from the apparent catalytic rate constants, ^Xk_cat which represent the catalytic effect of CFN. Larger values of or were observed for X = 4‐halobenzoate ions than that for X = 2‐halobenzoate ions due to isomeric factors. The values of or determined in the presence of TTABr were compared with previously determined or values in the presence of cetyltrimethylammonium bromide (CTABr). The values of or are nearly 8 ~ 9‐fold larger for 4‐IBz^?, 4‐BrBz^? and 4‐ClBz^? compared to the respective values of X = 2‐IBz^?, 2‐BrBz^? and 2‐ClBz^?. The values of or for X = 4‐FBz^? is nearly 3‐fold larger than that for X = 2‐FBz^?. The values of or for X = 2‐ and 4‐halobenzoates are significantly smaller in the presence of TTABr than these in the presence of CTABr nanoparticles.     

Surface,Micellar, and Aggregation Behavior of Non-cytotoxic Imidazolium Gemini Surfactants

The micellar, surface, and aggregation properties of biocompatible, imidazolium-based hydroxyl group-containing gemini surfactants, 1,1′-(propane-1,3-diyl-2-ol) bis(3-alkyl-1H-imidazol-3-ium)bromide, [C_nIm-3OH-ImC_n]Br₂, were studied. The surface parameters like maximum surface excess concentration at air/water interface (Γ_max), the minimum surface area occupied by surfactant molecules (A_min) and the related thermodynamic parameters such as, standard Gibbs free energy of micellization (), standard free energy of adsorption (), and free energy of surface at equilibrium ) were also determined from the surface parameters. The aggregation behavior has been elucidated from transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques which showed that these gemini surfactants have potential self-aggregation efficiency. Besides, some other physicochemical properties like foam stability, emulsifying power, and viscosity have been determined. The structural features of [C_nIm-3OH-ImC_n]Br₂ enhance their surface-active properties. These features of gemini surfactants are of primary significance from pharmaceutical and biomedical viewpoints. The gemini surfactants may have great implications in drug formulations and delivery owing to their prominent aggregation and non-cytotoxic nature.     

Micellar Properties of Surface Active Ionic Liquid Lauryl Isoquinolinium Bromide and Anionic Polyelectrolyte Poly(Acrylic Acid Sodium Salt) in Aqueous Solution

The complex formation between anionic polyelectrolyte poly(acrylic acid sodium salt) [NaPAA] and surface active ionic liquid (SAIL) lauryl isoquinolinium bromide [C₁₂iQuin][Br] in aqueous media has been investigated by surface tension, isothermal titration calorimetry (ITC), and conductance. The self‐assembled structures have been characterized using dynamic light scattering (DLS) and turbidity measurements. A range of surface parameters have been calculated from tensiometric measurements including critical micelle concentration (CMC), surface excess concentration (Γ_cmc), surface pressure at the interface (Π_cmc), minimum area occupied at air–solvent interface (A_min), adsorption efficiency (pC₂₀), and surface tension at the CMC (γ_cmc). The thermodynamic parameters, i.e., standard enthalpy of micellization , standard free energy of micellization (), and standard entropy of micellization () have also been evaluated. Four different stages of transitions, corresponding to the progressive formation of NaPAA–[C₁₂iQuin][Br] complex (C₁)_, critical aggregation concentration (CAC), critical saturation concentration (C₃) and CMC have been observed owing to strong electrostatic and hydrophobic interactions. The results obtained from DLS and turbidity measurements show that size of the aggregates first decreases and then increases in the presence of polyelectrolyte. The binding isotherms obtained using isothermal titration calorimetry (ITC) show the concentration dependence as well as the highly cooperative nature of interactions corresponding to formation of polyelectrolyte–SAIL complexes.     

Study of Micellization of Sodium Dodecyl Sulfate in Non-Aqueous Media Containing Lauric Acid and Dimethylsulfoxide

Interactions between dimethylsulfoxide (DMSO), lauric acid (LA) and anionic surfactant, sodium dodecyl sulfate (SDS) in non‐aqueous media have been studied in detail using conductometric, volumetric, and ultrasonic speed techniques. Conductivities, densities and ultrasonic speeds of 1 × 10^?3 to 11 × 10^?3 m SDS solutions in a mixture of LA (0.10 m) and DMSO between 298.15 and 313.15 K have been measured. The experimental data have been correlated against temperature and concentration of SDS using standard relations. The critical micelle concentration (CMC) values have been determined by using different methods like conductance, density and ultrasonic speed. All the methods yielded identical CMC values. The measured data were used to calculate various useful thermodynamic parameters like standard free energy, , enthalpy, , and entropy, , of micelle formation. From the density data of the surfactant, the change of the apparent molar volume upon micellization has been calculated. Density and ultrasonic speed data were used to evaluate the apparent molar adiabatic compressibility for the micelle of the surfactant at different temperatures over a wide concentration range.     

Synthesis,Characterization and Aqueous Properties of a New Hybrid Fluorocarbon Cationic Surfmer

A novel hybrid fluorocarbon cationic surfmer has been synthesized and its aggregation and surface properties have been studied by surface tension, electrical conductivity, steady‐state fluorescence, Rayleigh light scattering, dynamic light scattering and transmission electron microscopy. Through surface tension, electrical conductivity, steady‐state fluorescence and Rayleigh light scattering measurements, the effectiveness of surface tension reduction, the maximum surface excess concentration, the minimum area occupied per surfactant molecule at the air/water interface, the micropolarity and aggregation number of micelles were investigated. The results shows that the surfmer has superior surface activity and lower micropolarity than other surfmers. The critical micelle concentration at different temperatures and a series of thermodynamic parameters (, , and , , , and ) of micellization were evaluated. The thermodynamic parameters showed that the micelle formation was entropy‐driven in the temperature range of 15–40 °C. The size and morphology of the aggregates were also confirmed by dynamic light scattering and transmission electron microscopy.     

Volumetric, Compressibility, and Surface Tension Studies on Micellization Behavior of SDS in Aqueous Medium: Effect of Sugars

The densities , velocities of sound , and surface tension , of anionic surfactant sodium dodecyl sulfate in presence of aqueous saccharides (fructose and maltose) with concentrations 0.01 and 0.10 mol kg^?1 have been reported over a wide temperature range (293.15–313.15 K) at an interval of 5 K. The apparent molar volume , isentropic compressibility , and apparent molar adiabatic compression values have been calculated using densities and velocities of sound data. Both, and vary non‐linearly at lower concentration of surfactant and tend to achieve linearity at higher concentration of surfactant in presence of saccharides. From the surface tension data, parameters like surface excess , minimum area occupied by the surfactant molecule at the saturated air/solution interface and surface film pressure have been computed. The effect of additives on these parameters has been discussed in terms of different types of the interactions pertaining in the micellar system. An attempt has also been made to draw an inference regarding the effect of these additives on the critical micelle concentration of the surfactant.     

The Effect of Methanol on the Micellar Properties of Dodecyltrimethylammonium Bromide (DTAB) in Aqueous Medium at Different Temperatures

The micellar properties of dodecyltrimethylammonium bromide (DTAB) in water and methanol water mixtures at different temperatures have been studied by conductivity and surface tension measurements. The critical micelle concentrations (CMC), degree of ionization (α), standard Gibbs free energy of micellization (), standard enthalpy of micellization (), standard entropy of micellization () and free energy of transfer () were evaluated from conductivity data. The CMC, maximum excess surface concentration ( ), area occupied per surfactant molecule ( ), surface pressure at the CMC ( ), packing parameter (P) and standard free energy interfacial adsorption ) were estimated from surface tension measurements. The CMC of DTAB was found to increase with increasing volume fraction of methanol and increasing temperature. Thermodynamic parameters and surface properties revealed that the addition of methanol changes the relevant physicochemical properties which affect the process of micellization.     

Effect of Ethylene Oxide Group in the Anionic–Nonionic Mixed Surfactant System on Microemulsion Phase Behavior

The phase behavior of microemulsions stabilized by a binary anionic–nonionic surfactant mixture of sodium dihexyl sulfosuccinate (SDHS) and C12-14 alcohol ethoxylate (C_{12 − 14}E_j) that contains an ethylene oxide (E_j) group number, j, of either 1, 5, or 9 was investigated for oil remediation. The oil–water interfacial tension (IFT) and optimal salinity of the microemulsion systems with different equivalent alkane carbon numbers (EACN) were examined. The anionic–nonionic surfactant ratio was found to play a pivotal role in the phase transition, IFT, and optimal salinity. The minimum IFT of mixed SDHS − C_{12 − 14}E_j systems were about three times lower than those of neat SDHS systems. A hydrophilic–lipophilic deviation (HLD) empirical model for the mixed anionic–nonionic surfactant system with the characteristic parameter was proposed, as represented in the excess free energy term . The results suggested that the mixed system of SDHS − C_{12 − 14}E₁ was more lipophilic, while SDHS − C_{12 − 14}E₉ was more hydrophilic than the ideal mixture (no excess free energy during the microemulsion formation), and the SDHS − C_{12 − 14}E₅ system was close to the ideal mixture. The findings from this work provide an understanding of how to formulate mixed anionic–nonionic microemulsion systems using the HLD model for oils that possess a wide range of EACN.     

The Effect of Polar Head and Chain Length on the Physicochemical Properties of Micellization and Adsorption of Amino Alcohol-Based Surfactants

In this work, we have synthesized a series of quaternary ammonium from amino alcohols and n-bromoalkanes. The compounds are referred to as C_nEtOH, C_nPrOH, and C_niPrOH (where n = 12 and 14 carbons, EtOH = ethanol, PrOH = propanol, iPrOH = iso-propanol). Their structures were checked using the usual spectroscopic methods [¹H, ¹³C nuclear magnetic resonance (NMR) and infrared (IR)]. Their physicochemical properties in aqueous solution were studied using conductivity, surface tension, and ultra violet (UV)–visible absorption spectroscopy measurements. This study was conducted to show the effect of the linear hydrophobic chain and the location of the OH polar group with respect to the N⁺ quaternary ammonium on the physicochemical properties of the surfactants. The comparison between the physicochemical properties of the surfactants studied shows a distinct effect of the position of the OH group on the critical micelle concentration (CMC), the ionization degree (α), the area occupied at the interface (A_min), the free energy of adsorption (), and the free energy of micellization (). The intermolecular interaction between the synthetic surfactants and the methyl orange (OM) dye is related to the degree of hydration of the micelle, proven by the hypsochromic displacement of OM wavelength (λ_max) and ionization (α) of the micelles. The CMC, the degree of ionization, and the degree of hydration of the micelle follow the same trend.     

Influence of Additives and Temperature on the Interaction of Acid Red 151 Dye with Cetyltrimethylammonium Bromide: A Conductometric Study

The interaction of an anionic textile dye, acid red 151 (AR), with a cationic surfactant, cetyltrimethylammonium bromide (CTAB), in aqueous electrolyte medium (e.g., KCl, NaCl) and in H₂O + ethanol medium was observed using the conductometric method. Two critical micelle concentrations (CMC) were found for the AR + CTAB system in water and H₂O + ethanol medium, but only one CMC was detected for AR + CTAB in salt+H₂O media and for pure CTAB in all solutions. The change in CMC behavior of CTAB in the presence of AR indicates the occurrence of strong interaction between AR and CTAB. The extent of solubility increases with an increase of temperature, which disfavors micellization. The CMC values in NaCl solution are comparatively lower than those found in KCl solution, which signifies that the micelle formation is more favorable in attendance of NaCl. In aqueous ethanol solution, two CMC values were also observed for AR + CTAB that are higher than those obtained in water. The free energy of micellization () was negative, which illustrates a thermodynamically spontaneous micellization process. The values of enthalpy () and entropy () of micellization show that the process was entirely entropically driven at a lower temperature; but, enthalpic events are favored at elevated temperature in electrolyte medium, whereas both enthalpy and entropy are reduced in attendance of ethanol. In aqueous medium, the thermodynamic parameters signify the presence of electrostatic interaction between AR and CTAB at higher temperatures, while the hydrophobic interaction is the main driving force at a lower temperature. A linear expression of as a function of demonstrates enthalpy-entropy compensation over the experimental conditions employed in this study.     

Interaction of a Novel Anionic Gemini Surfactant Containing a Triazine Ring with Cetyltrimethylammonium Bromide in Aqueous Solution

The interaction between a novel anionic gemini surfactant containing a triazine ring, denoted as C8‐G, and cetyltrimethylammonium bromide (CTAB) has been investigated in aqueous solution. The surface tension vs log. molar concentration plots of the individual surfactants and their mixtures were measured at different temperatures (298, 303, 308, and 313 K) by the drop volume method. The surface properties and the interaction parameters of the adsorption monolayer and the mixed micelle were obtained from the plot. The results showed that the CMC of the C8‐G/CTAB mixture reached a minimum value of 3.20 × 10^?5 mol/L when α_G (the mole fraction of C8‐G in the mixed system) was 0.7 at 308 K, and the minimum γ_CMC was 28.1 mN/m obtained for the molar ratio of 0.9 at 308 K. Interaction between the two components was strongest () when α_G was 0.7 at 303 K. All the C8‐G/CTAB mixtures exhibited synergism in both surface tension reduction efficiency and mixed micelle formation except when the mole fraction of C8‐G (α_G) was 0.1, 0.5 and 0.9 at 313 K, and became greatest for the molar ratio of 0.7 at 303 K. The C8‐G/CTAB mixtures exhibited synergism in surface tension reduction effectiveness for all the complex ratios at 303 K, α_G = 0.1, 0.3, 0.9 at 308 K and α_G = 0.7 at 313 K, whereas the other surfactant mixtures did not show this synergism.     

Effect of Electrolytes and Correlations for Salinities at the Optimum Formulation of Sodium Dodecyl Benzene Sulfonate Microemulsions

The influences of different kinds of electrolytes on sodium dodecyl benzene sulfonate microemulsions were investigated in this work. Electrolyte cations had a strong influence on the microemulsion phase behavior. The higher the valence of the cation was, the stronger the influence of the electrolyte on the microemulsion phase inversion and the higher the optimum solubilization parameters, ordered as AlCl₃ > MgCl₂ > NH₄Cl > KCl > NaCl. The anion in electrolytes showed a relatively weak influence. The influences of anions with equal valence are almost the same for sodium salts, and a lower valence had a stronger impact on microemulsion phase inversion, ordered as Cl^? > CO₃^2? = SO₄^2? > PO₄^3?. The change of anions in sodium salts had little influence on the optimum solubilization parameters , all in the range of 5.301 ± 0.105 g_oil/g_surfactant. The efficiency ratio of electrolytes was defined based on the cationic charge concentration in mol/l. The efficiency ratios for electrolytes with monovalent cations were inversely proportional to (1 + Z_i), where Z_i is the anion valence, but this was not true for electrolytes with higher valence cations. For a microemulsion using electrolyte mixtures, the efficiency ratio shows a linear relationship with that of the component salts and the composition of the mixture.     

Elucidation of Interactions between l-Ascorbic Acid and Mixed Micellar Aggregates of Catanionic {Sodium Dodecylsulfate + Cetyltrimethylammonium Bromide} Surfactants via Physicochemical and Spectroscopic Studies

Surfactant micelles mimic the microenvironment present in biological systems and can act as a medium for antioxidant studies. Moreover, the thermodynamic profile of micellization and spectroscopic studies provides very good information about interactions in these systems. Thus, the mixed micellar behavior of sodium dodecylsulfate (SDS) and cetyltrimethylammonium bromide (CTAB) at varying mole fractions of SDS was studied in (0.01, 0.02, and 0.03) mol kg⁻¹ ʟ-ascorbic acid_(aq) solutions with the aid of various techniques viz., conductivity, density and sound velocity, and spectroscopy. From the CMC values of the mixed surfactants, the degree of ionization (β) and thermodynamic parameters (, , and ) were evaluated at 298.15, 308.15, and 318.15 K. The UV absorption spectra were recorded in (1–3) × 10⁻⁴ mol kg⁻¹ ʟ-ascorbic acid_(aq) solutions at various mole fractions of SDS. The proton (¹H) NMR spectra of mixed (SDS + CTAB) surfactants were studied in (0.01–0.03) mol kg⁻¹ ʟ-ascorbic acid solutions. Hydrodynamic diameters (D_h) of mixed micellar aggregates were obtained from the dynamic light scattering (DLS) studies. The present studies suggest the predominance of ionic-hydrophilic interactions between the ionic head groups {O-SO₃⁻ or N⁺ (CH₃)₃} of surfactants and the polar (–OH, –C=O and –O–) sites of ʟ-ascorbic acid.     

Influence of Different Additives on the Interaction of Quinolone Antibiotic Drug with Surfactant: Conductivity and Cloud Point Measurement Study

Conductometric and cloud point (CP) measurement studies have been performed to investigate the interaction of tetradecyltrimethylammonium bromide (TTAB) and Triton® X-100 (TX-100) with ciprofloxacin hydrochloride (CFH) in different solvents over the temperature range of 295.15–315.15 K. CFH is used for the treatment of various bacterial infections. The observed critical micelle concentration (CMC) values of TTAB were found to be reduced in the presence of electrolytes (Na₂SO₄/Na₃PO₄), and this reduction proceeds with the elevation of salt concentration. The order of the CMC of TTAB follows the trend: > >. The observed CMC values of TTAB were found to increase with increasing temperature and decrease with increasing concentration of CFH in aqueous medium. The values of Gibbs free energy of micellization () for the TTAB/TTAB + CFH mixture were found to be negative, implying spontaneous micellization. The estimated CP of TX-100 decreases with increasing concentration of TX-100 in aqueous medium. The CP values first decrease with increasing concentration of CFH and then increase at higher concentration of CFH almost in all cases investigated. The values of free energy of clouding were found to be positive in all cases studied implying that phase separation of TX-100 was nonspontaneous. The other thermodynamic parameters associated with the micellization of TTAB and the phase separation of TX-100 were estimated and explained.     

The Influence of an Organic Salt on Micellization Behavior of Tetradecyltrimethylammonium Bromide in Aqueous Solutions of Trisubstituted Ionic Liquid [Odmim][Cl]

The influence of sodium benzoate (Na-Bz) on micellization behavior of the cationic surfactant tetradecyltrimethylammonium bromide (TTAB) in aqueous media of trisubstituted imidazolium-based ionic liquid (IL), 1,2-dimethyl-3-octylimidazolium chloride [odmim][Cl], was investigated using conductometry, tensiometry, fluorescence,¹H NMR, Dynamic Light Scattering (DLS), and Rheology techniques. It was observed that with an increase in salt concentration, the critical micelle concentration (CMC) values of the system decrease. The CMC and various thermodynamic parameters like standard Gibbs free energy of micellization (), standard enthalpy change (), and standard entropy change () were calculated using conductometry and surface parameters such as surface pressure at the interface (П_cac), maximum surface excess concentration (Г_max), minimum surface area per molecule (A_min), and pC₂₀ (adsorption efficiency) were calculated using the tensiometry technique. The aggregation number (N_agg) was calculated using fluorescence measurements. ¹H NMR spectra shed light on interactions between the salt and the cationic surfactant in 0.1 wt% IL. DLS gives information about the size distribution of micelles in solution at different concentrations of salt.     

Aggregation Behavior of Sodium Dodecyl Sulfate and Cetyltrimethylammonium Bromide Mixtures in Aqueous/Chitosan Solution at Various Temperatures: An Experimental and Theoretical Approach

A conductometric study of the mixed micellization behavior between cetyltrimethylammonium bromide (CTAB, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic surfactant) was carried out in the absence/presence of various percentages of chitosan in the temperature range of 298.15–318.15 K. The deviations of critical micelle concentration (cmc) from the ideal values indicate the interaction between CTAB and SDS. The micellar mole fraction values according to different proposed models X₁^Rub (Rubingh), X₁^M (Motomura), X₁^Rod (Rodenas), and X₁^id (ideal mole fraction) were estimated and the results obtained reveal the high contribution of CTAB in the mixed micellization, which enhances with the increase of the mole fraction of CTAB. The negative magnitudes of indicate the spontaneous formation of mixed micelles between CTAB and SDS. The values of activity coefficients (f₁ and f₂) were less than unity and the values of the interaction parameter (β) are negative in all cases, which indicate the attractive interaction between CTAB and SDS. The negative values of excess free energy of micellization (ΔG_ex) signify the stability of the mixed micelles. The negative values of in the chitosan systems indicate that micellization is exothermic. The values of were found to be positive in all cases.