Micellar Aggregation Number Research Articles

Micellization, aggregation, interaction, and solubilization behaviors of mixed solutions of cationic gemini and nonionic surfactants

AbstractThe micellization properties of mixed aqueous solutions of a cationic gemini surfactant (CGS) and Triton X‐100, a conventional non‐ionic surfactant, with various mole fractions, were determined by measuring the surface tension at different temperatures. Various theoretical models were used to analyze the behavior of this mixed system. The interactions between CGS and Triton X‐100 were determined to be non‐ideal and synergistic. The calculated interaction parameters (βM) have negative values at all temperatures and for all mole fractions, showing attractive interactions. It was found that increasing the mole fraction of Triton X‐100 significantly increased the synergistic effect (more negative values). Micellar aggregation number (Nagg) values of pure surfactants and their mixtures in different ratios were obtained with the steady‐state fluorescence quenching method. Furthermore, the molar solubilization ratio of Sudan III organic dye in all surfactants aqueous systems was obtained using UV–Visible spectrophotometry. At concentrations above critical micelle concentration, the solubility of Sudan III in water was substantially increased linearly for all systems and it was observed that the enhancement was even more significant for mixed surfactant systems.

Scrutinizing micellar transitions and interfacial properties in mixed micelles comprising sodium dodecyl sulfate and sodium oleate: A tensiometric and scattering insight

Mixed micellar systems play a pivotal role in numerous scientific and industrial applications due to their inimitable solution properties and potential for enhancing solubilization and emulsification processes. The present study unveils the mixed micellization behavior of two anionically charged surfactants, sodium dodecyl sulfate (SDS) and sodium oleate (SO), in aqueous solutions through a combination of solution viscosity, tensiometric and small-angle neutron scattering (SANS) techniques. The dynamic changes in the interfacial properties of the mixed micellar system as a function of the SDS-to-SO ratio are evaluated from surface tension measurements. The results offer an insight into the formation of the stable mixed micelles with the alteration in the critical micelle concentration (CMC) as a function of the composition of both surfactants and the nature of the interaction. Surface tension data disclose the thermodynamic aspects of micelle formation and the influence of surfactant interactions on the surface activity of the system. Complementing the surface tension measurements, SANS analysis was conducted to clarify the structural aspects of the SDS-SO mixed micelles. SANS inferred the micellar size, shape, and aggregation number (Nagg), thereby shedding light on the nanoscale organization of the micellar aggregates in the aqueous solution. By combining SANS and surface tension data, a comprehensive understanding of the mixed micellization behavior of SDS and SO is achieved, addressing both interfacial and structural aspects. A computational simulation approach has also been employed to obtain the optimized parameters, which provide a better understanding of the correlation of SDS and SO molecular orbital energy levels. The results underscore the importance of surface tension and structural characterization techniques to comprehend the behavior of mixed micelles fully.

DPD simulations of anionic surfactant micelles: a critical role for polarisable water models.

We investigate the effects of polarisable water models in dissipative particle dynamics (DPD) simulations, focussing on the influence these models have on the aggregation behaviour of sodium dodecyl sulfate solutions. Studies in the literature commonly report that DPD approaches underpredict the micellar aggregation number of ionic surfactants compared to experimental values. One of the proposed reasons for this discrepancy is that existing water models are insufficient to accurately model micellar solutions, as they fail to account for structural changes in water close to micellar surfaces. We show that polarisable DPD water models lead to more realistic counterion behaviour in micellar solutions, including the degree of counterion disassociation. These water models can also accurately reproduce changes in the dielectric constant of surfactant solutions as a function of concentration. We find evidence that polarisable water leads to the formation of more stable micelles at higher aggregation numbers. However, we also show that the choice of water model is not responsible for the underestimated aggregation numbers observed in DPD simulations. This finding addresses a key question in the literature surrounding the importance of water models in DPD simulations of ionic micellar solutions.

Can sodium 1-alkylsulfonates participate in the sodium dodecyl sulfate micelle formation?

The aggregation behavior of sodium dodecyl sulfate (SDS) was studied in an aqueous solution in the presence of increasing concentrations of selected sodium 1-alkylsulfonates, namely sodium 1-octanesulfonate, sodium 1-decanesulfonate, and sodium 1-dodecanesufonate. The critical micelle concentration (CMC) of SDS was determined by conductivity and fluorescence intensity measurements. The steady-state fluorescence quenching experiments with pyrene as a fluorescent probe were performed to obtain micellar aggregation numbers (Nagg) of the surfactant. The thermodynamic parameters of micellization (ΔGmic0 for all studied systems; ΔHmic0 and ΔSmic0 for sodium 1-dodecanesufonate) have been determined and compared. The influence of alkyl chain length and concentration of the selected sodium 1-alkylsulfonates on the values of CMC, Nagg, ΔGmic0, ΔHmic0, and ΔSmic0 of SDS has been discussed. As it was found, all selected for the experiments electrolytes decrease significantly the CMC of the surfactant, while an opposite effect is observed for Nagg values. The obtained experimental results have been supported by theoretical calculations. Interestingly, it has been proven that solely the molecules of sodium 1-dodecanesufonate (of the same carbon chain length) may act as the SDS mimetics – they are not recognized by SDS as the ones with a different structure and consequently are allowed to participate in the formation of the surfactant’s micelles.

Effectiveness of the hydrophobic core of pyridine tethered N-acyl glycine micelles in improving chromenoquinoline synthesis in water

The organic transformations in water are considered a safe, non-toxic, economical, and eco-friendly alternative. A new series of amphiphile, N-acyl-N-(pyridin-2-ylmethyl)glycine (PyNAG) with variable hydrophobicity was successfully synthesized from glycine. The self-assembly properties were characterized by critical micellar concentration (CMC), aggregation number (Nagg), and diameter (DH). The PyNAG with N- stearoyl moiety showed lower CMC, higher Nagg, and larger DH compared to PyNAG with N- lauryl moiety. Molecular dynamics simulation reveals that the micelle structure is compact and non-bonded energy contribution arises from electrostatic, and van der Walls forces contribute to perfect packing and micelle formation. The ability of the PyNAG micelles to execute important organic transformations in water was demonstrated through synthesizing chromenoquinoline via the Povarov reaction. Micelles with varying diameters were used to conduct the Povarov reaction in order to better understand the functions of the hydrophobicity core of the micellar environment in organic reactions. The results reveal that the Povarov reaction produces a good yield in N-stearoyl-N-(pyridin-2-ylmethyl)glycine (PyN18G) micelles, better than organic solvent and commercial surfactant. Moreover, a linear correlation between the yield and the hydrophobicity of the PyNAG was observed. The findings demonstrate that the micellar interior significantly affects the reactivity of the substrate, which should be taken into consideration while creating new media for metal-catalyzed green synthesis.

Analytical modeling of micelle growth. 5. Molecular thermodynamics of micelles from zwitterionic surfactants

HypothesisThe critical micelle concentration, aggregation number, shape and length of spherocylindrical micelles in solutions of zwitterionic surfactants can be predicted by knowing the molecular parameters and surfactant concentrations. This can be achieved by upgrading the quantitative molecular thermodynamic model with expressions for the electrostatic interaction energy between the zwitterionic dipoles and micellar hydrophobic cores of spherical and cylindrical shapes. TheoryThe correct prediction of the mean micellar aggregation numbers requires precise calculations of the free energy per molecule in the micelles. New analytical expressions for the dipole electrostatic interaction energy are derived based on the exact solutions of the electrostatic problem for a single charge close to a boundary of spherical and cylindrical dielectric media. The obtained general theory is valid for arbitrary ratios between dielectric constants, radii of spheres and cylinders, positions, and orientations of dipoles. FindingsThe detailed numerical results show quantitatively the effects of the micelle curvature and dielectric properties of the continuum media on the decrease of the dipole electrostatic interaction energy. Excellent agreement was achieved between the theoretical predictions and experimental data for the critical micelle concentration, size and aggregation number of zwitterionic surfactant micelles. This study can be extended to mixed micelles of zwitterionic and ionic surfactants in the presence of salt to interpret and predict the synergistic effect on the rheology of solutions.

Micellization of conventional and gemini surfactants in aquoline: A case of exclusively water based deep eutectic solvent

Deep eutectic solvents (DES) based on water as the only hydrogen bond donor (HBD) have been introduced recently (aquoline). There is not a single report on surfactant association behaviour in aquoline. This study deals with the determination of physical properties (rheology, specific conductance, pH, micro polarity and apparent dielectric constant) of pure aquoline (with different molar ratios of choline chloride (ChCl): water, DES I - DES IV) and association behaviour of ionic surfactants in such aquoline systems. DESs were found Newtonian and highly polar / conducting fluids with nearly neutral pH (6.9–7.1). Micellization behaviour of different ionic surfactants (sodium dodecyl sulphate (SDS), sodium dodecane-1-sulphonate (SDSo), sodium dodecyl benzene sulphonates (SDBS), P, P'-1,4-butanedieyl, P, P'-didodecylester, disodium salt (12-4-12A), cetyltrimethylammonium ammonium bromide (CTAB) or dodecyl trimethyl ammonium bromide (DTAB)) has been studied fluorometrically in various aquolines and compare data with an aqueous medium. In most of the cases, critical micelle concentration (CMC) values have been found lower than water which may be due to the presence of choline chloride (ChCl, one of the components of aquoline), which can interact micelle electrostatically and hydrophobically. For different head groups in anionic surfactant, CMC follows the order 12-4-12A < SDBS < SDS < SDSo, which fits in the Hoffmeister like series of head groups. For cationic surfactants (CTAB and DTAB), CMC shows a similar chain length effect as observed in water. Overall, CMC data allow to propose that CMC decreases with an increase in molar content of water in a typical aquoline under eutectic limit. Micellar aggregation number (Nm), Stern-Volmer constant, micellar polarity, and apparent dielectric constant were also computed. It has been observed that micelles of lower Nm, with high polarity, are formed in a typical aquoline system (DES III). The study may find applications where organized assemblies are required in highly polar solvents.

Novel approach for tuning micellar characteristics and rheology of a sulfate-free anionic surfactant sodium cocoyl glycinate

Amino acid based mild and sulfate-free anionic surfactant, sodium cocoyl glycinate (SCGLY) forms spherical micellar aggregates in water. The mixed micellar characteristics of SCGLY has been studied in the presence of nonionic surfactants like cocamide diethanolamine (CDEA) and lauryl glucoside (LG). The ternary aqueous system of SCGLY/CDEA/LG depicts higher surface activity and stronger aggregation ability compared to corresponding single or binary surfactant systems as revealed by tensiometry. The effect of pH (5.5–6.5) and total surfactant concentration (14–18 wt%) on thickening of SCGLY/CDEA/LG system is studied by rheology measurements. The presence of CDEA/LG amid charged SCGLY head group shrinks the electrostatic repulsion and induces sphere-to-rod micellar transition depicting low or moderate viscosity under as-prepared neutral pH. With alteration in pH, viscosity augmented to a maximum (at pH ~5.8) followed by a viscosity decrease. This is a novel finding for mild sulfate-free SCGLY surfactant solution which otherwise is very hard to thicken. Micellar size and charge is attained by dynamic light scattering, while micellar shapes and aggregation numbers are determined by small-angle neutron scattering (SANS) measurements. Moreover, foaming behavior (foamability and stability) and mildness property (zein solubility) of SCGLY can be optimized as per the necessity in the presence of CDEA and LG. This work might prove to be an innovative approach to tune the micellar characteristics and rheology of amino acid based surfactant formulation which could be extremely beneficial for cost-effective, thickener-free, sulfate-free surfactant systems used in cleansing composition with desired viscosity.

Water effect in the reverse micellar formation of docusate sodium. A coarse-grained molecular dynamics approach

Improving understanding and characterization of complex fluid systems are crucial tasks of integral product and process design. Of particular interest is the development of enhanced surfactants for industrial and household applications. In this work, a coarse-grained molecular model is developed to study docusate sodium-water-cyclohexane microemulsion systems. Most of the model parameters are taken from a corresponding states treatment of the statistical associating fluid theory-γ-Mie equation of state, overcoming time-consuming simulations. A good agreement is found between model predictions and experimental data, including the phase boundary and reverse micellar aggregation numbers. The effect of water over the morphology of single reverse micelles was studied over the water:surfactant molar ratio range 1 – 14, where a predominant spherical shape was obtained with an average shape anisotropy value of 0.003. The gained molecular insights would be further exploited for the design of more efficient, effective and non-toxic surfactants.

Tuning the size of all-HPMA polymeric micelles fabricated by solvent extraction

The size of polymeric micelles crucially affects their tumor accumulation, penetration and antitumor efficacy. In the present study, micelles were formed based on amphiphilic poly(N-2-hydroxypropyl methacrylamide)-block-poly(N-2-benzoyloxypropyl methacrylamide) (p(HPMAm)-b-p(HPMAm-Bz)) via the solvent extraction method, and factors impacting micelle size were systematically studied, including the molecular weight of the polymers, homopolymer content, and processing methods (i.e., batch process versus continuous microfluidics). The formation of core-shell structured micelles was demonstrated by light scattering, sedimentation velocity and electron microscopy analysis. Micellar size and aggregation number increased with decreasing the molecular weight ratio of the hydrophilic/hydrophobic block. The presence of hydrophobic p(HPMAm-Bz) homopolymer and high copolymer concentration increased micelle size, while the presence of hydrophilic p(HPMAm) homopolymer did not affect micellar size. Regarding processing conditions, it was found that the use of tetrahydrofuran and acetone as solvents for the polymers resulted in larger micelles, likely due to their relatively high water-solvent interaction parameters as compared to other solvents tested, i.e., dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. Among the latter, only dimethylformamide led to micelles with a narrow polydispersity. Addition of dimethylformamide to an aqueous solvent and faster mixing of two solvents using microfluidics favored the formation of smaller micelles. In conclusion, our results show that the size of all-HPMA polymeric micelles can be easily tailored from 40 to 120 nm by varying the formulation properties and processing parameters.

Micellar properties of cetyltrimethylammonium bromide in an acetonitrile–water mixture: Conductometric and fluorescence studies

The effect of acetonitrile (ACN) on the micellization of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), in aqueous solutions at different temperatures was studied. The critical micellar concentration (CMC) as well as the degree of counter ion dissociation (a) of CTAB in aqueous ACN mixtures (10-20 % v/v) at various temperatures (291.2-298.2 K) were determined by electrical conductivity measurements, while steady-state fluorescence measurements were used to determine several CMCs (for comparison) and a micellar aggregation number (Nagg) as well. At a fixed temperature, both an increase in CMC and a decrease in Nagg were observed for an increase in ACN in the solvent mixture. With a temperature increase, CMC values increased for 10 % (v/v) ACN, while for both 15 % and 20 % (v/v) ACN, CMC values were a minimum at T = 295.2 K with a temperature increase. In addition, some aspects related to the Krafft temperature behavior of CTAB in the examined micellar systems are discussed.

Size-Dependent Drug Loading, Gene Complexation, Cell Uptake, and Transfection of a Novel Dendron-Lipid Nanoparticle for Drug/Gene Co-delivery.

Dendron micelles have shown promising results as a multifunctional delivery system, owing to their unique molecular architecture. Herein, we have prepared a novel poly(amidoamine) (PAMAM) dendron-lipid hybrid nanoparticle (DLNP) as a nanocarrier for drug/gene co-delivery and examined how the dendron generation of DLNPs impacts their cargo-carrying capabilities. DLNPs, formed by a thin-layer hydration method, were internally loaded with chemo-drugs and externally complexed with plasmids. Compared to generation 2 dendron DLNP (D2LNPs), D3LNPs demonstrated a higher drug encapsulation efficiency (31% vs 87%) and better gene complexation (minimal N/P ratio of 20:1 vs 5:1 for complexation) due to their smaller micellar aggregation number and higher charge density, respectively. Furthermore, D3LNPs were able to avoid endocytosis and subsequent lysosomal degradation and demonstrated a higher cellular uptake than D2LNPs. As a result, D3LNPs exhibited significantly enhanced antitumor and gene transfection efficacy in comparison to D2LNPs. These findings provide design cues for engineering multifunctional dendron-based nanotherapeutic systems for effective combination cancer treatment.

Do equilibrium and rate constants of intramicellar reactions depend on micelle size?

We have studied the combined static and dynamic quenching of pyrene by methyl viologen in sodium alkyl sulfate micelles varying in volume by a factor of more than 4. Size controls were the temperature T (283 K-333 K) and the alkyl chain length n (9-14) as well as, with n = 12 only, added NaCl (up to 9 times the surfactant weight-in concentration). At high [NaCl], up to 40% of the viologen resides in the aqueous bulk and quenches dynamically across the micelle-water interface with a rate limited by its diffusion-controlled attachment to the micelle. The micellar aggregation numbers depend linearly both on n and on the difference between T and the Krafft temperature; we have derived interpolation formulas for them as well as for the associated molar volumes of the micelles; the aggregation numbers at the critical micelle concentration are also linear functions of T, and the exponent relating them to the aggregation numbers at other concentrations is temperature independent. At given T, the volume-based quenching rate constants for different n or [NaCl] are very similar, and the same holds true for the equilibrium constants of the static quenching. Arrhenius plots identify the microviscosity inside the micelles as octanol-like; van't Hoff plots give virtually the same reaction enthalpies and entropies as in homogeneous methanolic solution; and the underlying kinetic and thermodynamic parameters are not modified by the micelle size.

SLES/CMEA mixed surfactant system: Effect of electrolyte on interfacial behavior and microstructures in aqueous media

In aqueous anionic sodium lauryl ether sulfate (SLES) solution, presence of nonionic cocamide monoethanolamine (CMEA) depicts intriguing interfacial and bulk properties. CMEA has poor water solubility but can be readily solubilized in SLES solution to form mixed micellar aggregates as revealed by surface tension measurements. Sphere-to-rod micellar transition in aqueous SLES-CMEA binary mixtures occurs at higher surfactant concentration (total surfactant concentration beyond 15 wt%), inducing a sharp growth in the viscosity (>1000 cP). Nevertheless, adding NaCl in SLES-CMEA mixtures, substantial growth in viscosity is perceived at much lower surfactant concentration (~5–10 wt%) attributed to the formation of intertwined worm-like micelles. Micellar sizes were obtained by dynamic light scattering (DLS) measurements and small-angle neutron scattering (SANS) investigations is used to determine micellar shapes and aggregation number for SLES-CMEA mixtures. Furthermore, it is observed that foaming behavior of SLES can be modulated by CMEA ascribed to the change in foam film rigidity. Corresponding experiments were also performed with nonethoxylated counterpart sodium lauryl sulfate (SLS) under analogous condition for comparison. The study reported here may prove to be an appropriate tactic to alter not only the rheology or foaming behavior of SLES-CMEA mixed surfactant system but also provide pre-solubilized composition of CMEA which could be highly beneficial for personal care products enabling CMEA blending at room temperature, which otherwise needs high temperature mixing.

Studies on the self-aggregation, interfacial and thermodynamic properties of a surface active imidazolium-based ionic liquid in aqueous solution: Effects of salt and temperature

The influence of four sodium salts (NaCl, NaBr, Na2SO4, and Na3PO4) on the self-aggregation, interfacial, and thermodynamic properties of a surface active ionic liquid (1-hexadecyl-3-methylimidazolium chloride, C16MImCl) has been explored in aqueous solutions by conductometry, tensiometry, spectrofluorimetry, isothermal titration calorimetry and dynamic light scattering (DLS). Analyses of the critical micellar concentration (cmc) values indicate that the anions of the added salts promote the self-aggregation of C16MImCl in the order: Cl− < Br− < PO43−< SO42−. Dehydration of imidazolium head groups, in general, governs the process of micellization of aqueous C16MImCl in presence of the investigated salts within the investigated temperature range (298.15–318.15 K), while the melting of iceberg takes the leading role below 303.15 K for the C16MImCl-Na3PO4 system. The results indicate that addition of salt leads to a greater spontaneity of micellization, and that exothermicity prevails in these systems. Differential effect of the salts on the interfacial properties of C16MeImCl has been interpreted on the basis of the coupled influence of the electrostatic charge neutralization of surfactants at the interface, and the van der Wa-als repulsion of surfactant tails and electrostatic repulsion of surfactant head groups. C16MeImCl has been predicted to form spherical micelles in presence of varying amounts of NaCl, Na2SO4 and Na3PO4, while there occurs probably a transition in the micellar geometry from spherical to non-spherical shape when added NaBr concentration exceeds 0.01 mol.kg−1. Fluorescence studies demonstrate that a combined quenching mechanism is operative for the quenching of pyrene fluorescence in the investigated C16MImCl-salt systems. Micellar aggregation numbers obtained from Steady State Fluorescence Quenching method have always been found be somewhat smaller than those estimated from Time Resolved Fluorescence Quenching method. The order of instability of the C16MImCl-micelles ascertained from Zeta potential measurements conform to what has been inferred from the cmc values. The hydrodynamic diameters of C16MImCl-micelles, obtained from DLS studies, have been found to increase with increasing salinity of the solutions.

Equilibrium model for estimating micellar aggregation number from surface equation

The Aggregation Surface Equation (ASE) is attained by coupling the Gibbs adsorption equation and surface aggregation isotherm. The resulting equation can be used to study fluid-fluid interfaces in connection with the micelle formation process. This new equation contains two boundary conditions in the vicinity of the saturation region: (i) the critical micelle concentration (CMC), which corresponds to the onset of micelle formation; and (ii) the critical spherical micelle concentration (CSC) (i.e. the completion of spherical micellar aggregates). These boundary conditions, which appear within a narrow surfactant concentration range, provide the basis to calculate the average aggregation number under the assumption of constant average aggregation number and spherical micelles geometry. The resulting Surface Equation (SE) contains the maximum surface concentration of the surface monolayer, the critical micelle concentration and the micelle average aggregation number. The mass action law allows extending the ASE as a function of the free monomer, as opposed to the total or nominal surfactant concentration, which was recently performed in the STAND model (Langmuir, 32, (16), (2016), 3917-3925). This paper presents a simple and direct method to calculate the micellar average aggregation number from surface tension data and the proposed surface equation.

Micellar Aggregation Behavior of Alkylaryl Sulfonate Surfactants for Enhanced Oil Recovery.

Alkylaryl sulfonate is a typical family of surfactants used for chemically enhanced oil recovery (EOR). While it has been widely used in surfactant–polymer flooding at Karamay Oilfield (40 °C, salinity 14,000 mg/L), its aggregation behavior in aqueous solutions and the contribution of aggregation to EOR have not been investigated so far. In this study, raw naphthenic arylsulfonate (NAS) and its purified derivatives, alkylaryl monosulfonate (AMS) and alkylaryl disulfonate (ADS), were examined under simulated temperature and salinity environment of Karamay reservoirs for their micellar aggregation behavior through measuring surface tension, micellar size, and micellar aggregation number. It was found that all three alkylaryl sulfonate surfactants could significantly lower the surface tension of their aqueous solutions. Also, it has been noted that an elevation both in temperature and salinity reduced the surface tension and critical micellar concentration. The results promote understanding of the performance of NAS and screening surfactants in EOR.

Mixed Micellar and Interfacial Studies of Triblock Copolymers with Amphiphilic Drug Ibuprofen in Aqueous Urea Solutions

AbstractMixed micellar and surface properties of non‐ionic triblock copolymers (Pluronic® P123 and F68) and non‐steroidal anti‐inflammatory drug Ibuprofen (IBF) have been evaluated in aqueous urea (100 mM) solutions with the help of surface tension and fluorescence measurements at 298.15 K. Various bulk and surface parameters such as critical micelle concentration (CMC) of the mixtures, micellar mole fraction (X), interaction parameter (β) and free energies were calculated using Clint, Rubingh, Rosen and Maeda models. In aqueous solutions, all the mixtures show synergistic interactions and are more in mixtures of IBF with P123. These interactions decrease in presence aqueous urea solution due to breaking of water structure surrounding the hydrophobic moieties by urea molecules resulting in delayed mixed micellization. Micellar aggregation number (Nagg) obtained from the steady state fluorescence quenching indicate that the participation of triblock copolymer is more than the drug IBF in mixed micelle formation. Stern‐Volmer constant (KSV), dielectric constant (Dexp), and micropolarity (I1/I3) have also been evaluated and their contribution in the mixed micellar systems have been discussed.

Fluorescence Study of Aggregation Behaviour of Cationic Surfactant Carbethopendecinium Bromide and its Comparison with Cetyltrimethylammonium Bromide

Abstract The aggregation behaviour of the cationic surfactant carbethopendecinium bromide (Septonex) and cetyltrimethylammonium bromide (CTAB) in aqueous solution was investigated by steady-state and time-resolved fluorescence experiments. Values of critical micelle concentration were obtained from the pyrene emission polarity index. The micellar aggregation numbers for four different concentrations of both surfactants were determined by steady-state and time-resolved fluorescence quenching methods, using pyrene as a probe and cetylpyridinium chloride as a quencher. The results obtained for Septonex were compared with the aggregation parameters of CTAB. Generally, Septonex micelles were formed by a smaller number of surfactant monomers than in the case of CTAB and the critical micelle concentration of Septonex is lower than that of CTAB. Also, the concentration dependence of the micelle aggregation number was found.

Effect of highly hydrophobic plant oil-based monomers on micellization of sodium dodecyl sulfate

The effect of highly hydrophobic olive oil-based (OVM) and high oleic soybean oil-based (HO-SBM) acrylic monomers on micellization of sodium dodecyl sulfate (SDS) was examined at different surfactant and monomer concentrations by determining micellar parameters, size and structure, as well as surface tension measurements. The obtained results indicate SDS ability to solubilize sparingly soluble in water plant oil-based monomer (POBM) molecules and facilitate formation of mixed (SDS/POBM) micelles. Surface activity of a surfactant/monomer mixture varies by adding the POBM and is generally higher than for SDS. Comprehensive trends were observed for micellar aggregation number and number of micelle-bound monomer molecules demonstrating that POBM molecules replace SDS counterparts in the mixed micelles. Based on dynamic light scattering measurements (DLS), we hypothesized that incorporation of POBM into the mixed micelles promotes micellar association and formation of 25–30 nm size structures, also detected using transmission electron microscopy (TEM). Practical importance of these findings is the fact that solubilization of POBM by surfactant molecules can have an impact on reaction kinetics and mechanism of emulsion polymerization, as well as affect latex particles formation and, respectively, resulting particle morphology.