Electrolyte effect on adsorption and the phase transition from microstructures to nanostructures in ionic/ionic surfactants mixture

The effect of salt concentration on intermicellar interactions and aggregate structures of anionic and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) were investigated with conductometry, surface tension, zeta potential, cyclic voltammetry measurements and by determining the surfactant NMR self-diffusion coefficients. The critical aggregate concentration (CAC), surface excess (Γ(max)), and mean molecular surface area (A(min)) were determined from plots of the surface tension (γ) as a function of the log of total surfactant concentration. The electrochemical behavior of cationic-anionic (catanionic) mixed surfactant and self-assembled surfactant monomers at Pt wire electrode were studied by cyclic voltammetry (CV). A variation in the peak current versus the total concentration of surfactant allow us to evaluate the CAC and related parameters from regular solution theory along with the diffusion coefficient of the electroactive species. It was observed that, for both the planar air/aqueous interface and micellar systems, the nonideality decreased as the amount of electrolyte in the aqueous medium was increased. Finally, we investigated the variations of electrostatic, transfer and steric free energy in phase transition between mixed micelle and vesicle in the presence of electrolyte using the presented model by our groups.     

Depletion flocculation of latex dispersion in ionic micellar systems

The flocculation behavior of anionic and cationic latex dispersions induced by addition of ionic surfactants with different polarities (SDS and cetyltrimethylammonium bromide (CTAB)) have been evaluated by rheological measurements. It was found that in identical polar surfactant systems with particle surfaces of SDS + anionic lattices and CTAB + cationic lattices, a weak and reversible flocculation has been observed in a limited concentration region of surfactant, which was analyzed as a repletion flocculation induced by the volume-restriction effect of the surfactant micelles. On the other hand, in oppositely charged surfactant systems (SDS + cationic lattices and CTAB + anionic lattices), the particles were flocculated strongly in a low surfactant concentration region, which will be based on the charge neutralization and hydrophobic effects from the adsorbed surfactant molecules. After the particles stabilized by the electrostatic repulsion of adsorbed surfactant layers, the system viscosity shows a weak maximum again in a limited concentration region. This weak maximum was influenced by the shear rate and has a complete reversible character, which means that this weak flocculation will be due to the depletion effect from the free micelles after saturated adsorption.     

Mixed micelles of polyethylene glycol (23) lauryl ether with ionic surfactants studied by proton 1D and 2D NMR

(1)H NMR chemical shift, spin-lattice relaxation time, spin-spin relaxation time, self-diffusion coefficient, and two-dimensional nuclear Overhauser enhancement (2D NOESY) measurements have been used to study the nonionic-ionic surfactant mixed micelles. Cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) were used as the ionic surfactants and polyethylene glycol (23) lauryl ether (Brij-35) as the nonionic surfactant. The two systems are both with varying molar ratios of CTAB/Brij-35 (C/B) and SDS/Brij-35 (S/B) ranging from 0.5 to 2, respectively, at a constant concentration of 6 mM for Brij-35 in aqueous solutions. Results give information about the relative arrangement of the surfactant molecules in the mixed micelles. In the former system, the trimethyl groups attached to the polar heads of the CTAB molecules are located between the first oxy-ethylene groups next to the hydrophobic chains of Brij-35 molecules. These oxy-ethylene groups gradually move outward from the hydrophobic core of the mixed micelle with an increase in C/B in the mixed solution. In contrast to the case of the CTAB/Triton X-100 system, the long flexible hydrophilic poly oxy-ethylene chains, which are in the exterior part of the mixed micelles, remain coiled, but looser, surrounding the hydrophobic core. There is almost no variation in conformation of the hydrophilic chains of Brij-35 molecules in the mixed micelles of the SDS/Brij-35 system as the S/B increases. The hydrophobic chains of both CTAB and SDS are co-aggregated with Brij-35, respectively, in their mixed micellar cores.     

Self-assembly of surfactant vesicles that transform into viscoelastic wormlike micelles upon heating

Unilamellar vesicles are observed to form in aqueous solutions of the cationic surfactant, cetyl trimethylammonium bromide (CTAB), when 5-methyl salicylic acid (5mS) is added at slightly larger than equimolar concentrations. When these vesicles are heated above a critical temperature, they transform into long, flexible wormlike micelles. In this process, the solutions switch from low-viscosity, Newtonian fluids to viscoelastic, shear-thinning fluids having much larger zero-shear viscosities (e.g., 1000-fold higher). The onset temperature for this transition increases with the concentration of 5mS at a fixed CTAB content. Small-angle neutron scattering (SANS) measurements show that the phase transition from vesicles to micelles is a continuous one, with the vesicles and micelles coexisting over a narrow range of temperatures. The tunable vesicle-to-micelle transition and the concomitant viscosity increase upon heating may have utility in a range of areas, including microfluidics, controlled release, and tertiary oil recovery.     

Compositional effects on electrophoretic and chromatographic figures of merit in electrokinetic chromatography with cetyltrimethylammonium bromide/sodium octyl sulfate vesicles as the pseudostationary phase. Part 1: effect of the phase ratio

The effect of the phase ratio on the electrophoretic and chromatographic properties of unilamellar vesicles comprised of cetyltrimethylammonium bromide (CTAB) and sodium octyl sulfate (SOS) was investigated in EKC. The surfactant concentration of the vesicles was 0.9, 1.2, 1.5, and 1.8% w/v, with a mole ratio of 1:3.66 (CTAB/SOS). Results were compared to those obtained using SDS micelles at concentrations of 1.0% (w/v, 35 mM) and 1.5% (52 mM). The CTAB/SOS vesicles (0.9-1.8% w/v) provided a significantly larger elution range (5.7 < or = t(ves)/t(0) < or = 8.7) and greater hydrophobic (methylene) selectivity (2.8 < or = alpha(CH2) < or = 3.1) than SDS micelles (3.1 < or = t(mc)/t(0) < or = 3.3; alpha(CH2) = 2.2). Whereas the larger elution range can be attributed to the 25% reduction in EOF due to the interaction of unaggregated CTAB cations and the negatively charged capillary wall, the higher methylene selectivity is likely due to the lower concentration of water expected in the CTAB/SOS vesicle bilayer compared to the Palisades layer of SDS micelles. For a given phase ratio, CTAB/SOS vesicles are somewhat less retentive than SDS micelles, although retention factors comparable to those observed in 1.0-1.5% SDS can be obtained with 1.5-1.8% CTAB/SOS. A linear relationship was observed between phase ratio and retention factor, confirming the validity of the phase ratio model for these vesicles. Unique polar group selectivities and positional isomer shape selectivities were obtained with CTAB/SOS vesicles, with both types of selectivities being nearly independent of the phase ratio. For four sets of positional isomers, the elution order was always para < ortho < meta. Finally, the thermodynamics of solute retention was qualitatively similar to that reported for other surfactant aggregates (micelles and microemulsions); the enthalpic contribution to retention was consistently favorable for all compounds, whereas the entropic contribution was favorable only to hydrophobic solutes.     

Properties of polyethylene glycol (23) lauryl ether with cetyltrimethylammonium bromide in mixed aqueous solutions studied by self-diffusion coefficient NMR

NMR self-diffusion coefficient measurements have been used to study the properties of polyethylene glycol (23) lauryl ether (Brij-35) with cetyltrimethylammonium bromide (CTAB) in the mixed aqueous solutions with different mole fractions of CTAB. By fitting the self-diffusion coefficients to the two-state exchange model, the critical micelle concentrations of the two solutes in the mixed solutions (cmc*1 and cmc*2) were obtained. The critical mixed micelle concentrations (cmc*) were then evaluated by the sum of cmc*1 and cmc*2, which are in good agreement with the results measured by the surface tension method. The cmc* values are lower than those of the ideal case of mixing, which indicates that the behavior of the CTAB/Brij-35 system is nonideal. Moderate interactions between CTAB and Brij-35 in their mixtures can be deduced from the interaction parameters (betaM) based on the cmc* obtained by the NMR self-diffusion method. The compositions (x1) of the mixed micelles at different total surfactant concentrations were also evaluated. By using these results, a possible mechanism of mixed micellar formation and a picture of the formation of nonsimultaneous CTAB/Brij-35 binary mixed micelle were proposed. In contrast to the case of CTAB/TX-100 system, Brij-35 molecules have a tendency to form micelles first at any mole fraction of CTAB. The mixed micellar self-diffusion coefficients (Dm) increase slightly at lower CTAB molar ratios, and then speed up with increasing CTAB mole fraction.     

Spectrophotometric study of interaction and solubilization of procaine hydrochloride in micellar systems

The interaction of Procaine hydrochloride (PC) with cationic, anionic and non-ionic surfactants; cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and triton X-100, were investigated. The effect of ionic and non-ionic micelles on solubilization of Procaine in aqueous micellar solution of SDS, CTAB and triton X-100 were studied at pH 6.8 and 29°C using absorption spectrophotometry. By using pseudo-phase model, the partition coefficient between the bulk water and micelles, K_x, was calculated. The results showed that the micelles of CTAB enhanced the solubility of Procaine higher than SDS micelles (K_x = 96 and 166 for SDS and CTAB micelles, respectively) but triton X-100 did not enhanced the solubility of drug because of weak interaction with Procaine. From the resulting binding constant for Procaine-ionic surfactants interactions (K_b = 175 and 128 for SDS and CTAB surfactants, respectively), it was concluded that both electrostatic and hydrophobic interactions affect the interaction of surfactants with cationic procaine. Electrostatic interactions have a great role in the binding and consequently distribution of Procaine in micelle/water phases. These interactions for anionic surfactant (SDS) are higher than for cationic surfactant (CTAB). Gibbs free energy of binding and distribution of procaine between the bulk water and studied surfactant micelles were calculated.      

Molecular interactions of cationic and anionic surfactants in mixed monolayers and aggregates

The properties of anionic-rich and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) were investigated with conductometry and surface tension measurements and by determining the surfactant NMR self-diffusion coefficients. The critical aggregate concentration (CAC), surface tension reduction effectiveness(gamma(CAC)), surface excess(Gamma(max)), and mean molecular surface area (A(min)) were determined from plots of the surface tension (gamma) as a function of the total surfactant concentration. The compositions of the adsorbed films (Z) and aggregates (chi) were estimated by using regular solution theory, and then the interaction parameters in the aggregates (beta) and the adsorbed film phases (beta(sigma)) were calculated. The results showed that the synergism between the surfactants enhances the formation of mixed aggregates and reduces the surface tension. Further, the nature and strength of the interaction between the surfactants in the mixtures were obtained by calculating the values of the following parameters: the interaction parameter, beta, the size parameter, rho, and the nonrandom mixing parameter, P*. These results indicate that in ionic surfactant mixtures the optimized packing parameter has the highest value and that the size parameter can be used to account for deviations from the predictions of regular solution theory. It was concluded that, for planar air/aqueous interfaces and aggregation systems, this nonideality increases as the temperature increases. This trend is attributed to the increased dehydration of the surfactant head groups that results from increases in temperature. Further, our conductometry measurements show that the counterion binding number of mixed micelles formed in mixtures with a high CTAB content is different to those with a high SDS content. This difference is due to either their different aggregation sizes or the different interactions between the head groups and the counterions.     

Quantitating the association of charged molecules with ionic micelles

We have studied micelles comprised of cationic (CTAB) and anionic (SDS) surfactants through the interactions of solution phase anionic disodium fluorescein (DSF) and cationic rhodamine 110 (R110) dyes with perylene sequestered within the micelles. Fluorescence lifetime measurements monitor energy transfer between the nonpolar optical donor within the micelle and ionic probes in the surrounding solution. The efficiency of this process is mediated by the extent to which the ionic dyes interact with the micelle palisade layer, and our fluorescence lifetime data allow us to determine the association constants for acceptor-micelle interactions.     

Influence of ionic charges on the bilayers of lamellar phases

The influence of ionic charges on the mesophases in the ternary system of C(12-16)E(6) (LA 070), ethylhexylglycerid (EHG), and water was studied. The charge was introduced by adding the ionic surfactant SDS (sodium dodecyl sulfate). The single lamellar phase (5 wt % LA 070 and 240 mM EHG in water) yields a bluish homogeneous solution. With the addition of SDS, the samples become more and more clear. Rheology measurements indicate that increased charge density increases the storage modulus G', and the lamellar phases show typical behavior of a viscoelastic fluid with a yield stress at higher SDS concentration. SAXS measurements show that the interlamellar distance D decreases with SDS concentration. The addition of ionic surfactants suppresses the Helfrich undulations, flattens the bilayers, and decreases interbilayer spacing due to electrostatic repulsions of the ionic surfactant head groups. Furthermore, the L(alpha) phase transforms into vesicle phases as the SDS concentration is increased. Second, it is shown that with added NaCl electrolyte the phase with charged surfactant behaves again in the same way as the initial uncharged system. The addition of salt screens the electrostatic interaction, which leads to a higher flexibility of the bilayers and a decrease of the storage modulus G'. Theoretical calculations show that the shear moduli of the L(alpha) phases are much smaller than the osmotic pressure of the systems. Several models are proposed for the explanation of the shear moduli. The model due to Lekkerkerker for the electric contribution of the bending constant of the bilayer seems to yield good results for the transition to vesicles.     

Optical spectroscopic and TEM studies of catanionic micelles of CTAB/SDS and their interaction with a NSAID

If a vesicle is a better model of a membrane in the context of the hydrophobic effect, then from the charge distribution point of view, a catanionic micelle is a closer model to a biomembrane. We have prepared and characterized two different types of catanionic micelles of sodium dodecyl sulfate (SDS) and cetyl N,N,N-trimethylammonium bromide (CTAB) having different surface charge ratios using optical spectroscopy and transmission electron microscopy. The average size of both types of mixed micelles was found to be much larger than that of micelles containing uniformly charged headgroups. Catanionic micelles containing higher concentrations of positively charged headgroups (CTAB) are larger in size, less compact, and more polar compared to the micelles containing higher concentrations of negatively charged headgroups (SDS). We have used these catanionic micelles as membrane mimetic systems to understand the interaction of piroxicam, a nonsteroidal anti-inflammatory drug (NSAID) of the oxicam group, with biomembranes. In continuation of our work on membrane mimetic systems, we have used spectral properties of the drug itself to understand the effect of the presence of mixed charges on the micellar surface in guiding the interaction of catanionic micelles with piroxicam. Our earlier studies of the interaction of piroxicam with micelles having uniform surface charges have shown that the charge on the micellar surface not only dictates which prototropic form of the drug will be incorporated in the micelles but also induces a switch-over between different prototropic forms of piroxicam. The equilibrium of this switch-over is extremely sensitive to the environment. In this study, we demonstrate how even small changes in the electrostatic forces obtained by doping the uniformly charged surface of the micelles with oppositely charged headgroups (as in catanionic micelles) are capable of fine-tuning this equilibrium. This implies that the surface charge of biomembranes, which are quite diverse in vivo, might play a significant role in selecting a particular form of the drug to be presented to its targets.     

Zeta-potentials of self-assembled surface micelles of ionic surfactants adsorbed at hydrophobic graphite surfaces

The zeta-potentials of the self-assembled surface ionic surfactants (sodium dodecyl sulfate—SDS and hexadecyltrimethyl ammonium bromide—CTAB) on graphite surfaces were determined both from streaming potential and electrophoretic mobility measurements. The adsorption of the surfactants at graphite–liquid interfaces has been studied using atomic force microscopy (AFM) soft-contact imaging which shows the formation of linear, parallel hemicylinders with headgroups oriented towards the solution. The magnitude of the zeta-potential increased with an increase in surfactant concentration, reaching a constant value at a concentration corresponding to the point of surface micelle formation as confirmed from AFM imaging. The streaming potential and electrophoretic mobility measurements showed that the zeta-potentials of SDS and CTAB surface micelles adsorbed at the graphite surface were about −75 and +70 mV, respectively, well in agreement with the values reported for bulk phase micelles in the literature.     

The significant effects of linear medium chain fatty alcohols on phase behavior of aqueous solution of mixed cationic–anionic surfactant

The effect of 1-hexanol on the phase behavior of aqueous solutions of sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) has been systematically studied. The phase ranges of vesicle and liquid crystal (LC) can be greatly extended with the addition of 1-hexanol. These specific structures distributed symmetrically on the two sides of the SDS/CTAB equimolar line in the pseudo ternary phase diagram. The aqueous two phase system (ATPS) contained vesicles that would transform into lamellar LC with the change of ratio of SDS/CTAB. The phase behaviors of SDS/CTAB system with addition of different alcohols (C₅OH–C₈OH) showed similar trends in structural transition except for phase span, demonstrating that the obstruction of electrostatic interaction between surfactant polar heads was affected by the insertion depth of the added alcohols.     

Investigation of the chiral surfactant N-dodecoxycarbonylvaline in electrokinetic chromatography: improvements in elution range and pH stability via mixed micelles and vesicles, and the hydrophobicity determination of basic pharmaceutical drugs

The chiral surfactant dodecoxycarbonylvaline (DDCV) has proven to be an effective pseudostationary phase for the separation of many enantiomeric pharmaceutical compounds. In this study the elution range and the prediction of octanol-water partitioning for the DDCV micellar system was examined. Through incorporation of DDCV in mixed micelles and unilamellar vesicles, enhancement of the elution range was observed. The mixed micelles contained a second anionic surfactant, sodium dodecyl sulfate (SDS), while the vesicles were composed of DDCV and the cationic surfactant cetyltrimethylammonium bromide (CTAB). Enantioselectivity, as well as other chromatographic and electrophoretic parameters, were compared between the mixed micelles, vesicles, and DDCV micelles. The hydrophobicity of the DDCV system was also evaluated as a predictor of n-octanol-water partition coefficients for 15 beta amino alcohols. The correlation between the logarithm of the retention factor (log k) and log P(ow) for seven hydrophobic beta-blockers and eight beta-agonists were r2 = 0.964 and r2 = 0.814, respectively.     

Effect of the electrostatic charge on the mechanism inducing liposome solubilization: a kinetic study by synchrotron radiation SAXS

The anionic surfactant sodium dodecyl sulfate (SDS) was used to induce the initial steps of the solubilization of liposomes. The structural transformations as well as the kinetics associated with this initial period were studied by means of time-resolved small-angle X-ray scattering (SAXS) using a synchrotron radiation source. Neutral and electrically charged (anionic and cationic) liposomes were used to investigate the effect of the electrostatic charges on the kinetics of these initial steps. The mechanism that induces the solubilization process consisted of adsorption of surfactant on the bilayers and desorption of mixed micelles from the liposomes surface to the aqueous medium. In all cases the time needed for desorption of the first mixed micelles was shorter than that for complete adsorption of the surfactant on the liposomes surface. The present work demonstrates that adsorption of the SDS molecules on negatively charged liposomes was slower and release of mixed micelles from the surface of these liposomes was faster than for neutral liposomes. In contrast, in the case of positively charged liposomes, the adsorption and release processes were, respectively, faster and slower than those for neutral vesicles.     

Interaction between silicates and ionic surfactants in dilute solution

Understanding the interaction between silicate ions and surfactants is critical for the design and development of mesoporous siliceous materials. We examined the interaction between sodium silicate ions and three different cationic surfactants [namely, cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB), and dodecyltrimethylammonium bromide (DTAB)] and an anionic surfactant [sodium dodecyl sulfate (SDS)] in dilute solution at room temperature. From the combination of several techniques, such as conductometric and potentiometric titrations, dynamic light scattering, and isothermal titration calorimetry, the phase behavior of the sodium silicate and CTAB system was determined. We observed that the aggregation behavior of the silicate-CTAB system is similar to that of a polymer-surfactant system. The formation of the silicate-CTAB complex is induced by the adsorption of SiOH and SiO- groups, aided by CTAB unimers. The electrostatic attraction and hydrophobic interaction are the dominant forces controlling the formation of silicate-CTAB complexes. When these complexes are saturated with CTAB unimers, free CTAB micelles are then produced. TEM micrographs revealed that a stable Si-O-Si network is absent within the silicate-CTAB complexes, and surprisingly, stable silicate-CTAB complexes with ordered structure were observed. The present finding is important for understanding the interaction between silicate and surfactant in the synthesis of mesoporous structure in the dilute solution regime.     

SDS对SB3-12胶束表面电荷密度的调控作用及对药物增溶的影响

两性离子甜菜碱表面活性剂(SB3-12)胶束具有较好的生物相容性,由于相反电荷的极性头之间具有静电中和作用,胶束表面具有小的负电荷密度。当加入阴离子的十二烷基硫酸钠(SDS)以后,负离子SD-与SB3-12胶束极性区内层季铵正电荷的静电中和作用,能连续地调节胶束表面磺酸基的负电荷密度,这有利于对药物分子的选择性增溶和调节在生理条件下的药物的输送。等温滴定量热(ITC)研究发现SB3-12和SDS有强的协同效应,混合临界胶束浓度(CMC)和胶束化焓明显降低,并得到两者协同效应的弱静电作用机理。当模型药物分子芦丁(Rutin)与SB3-12/SDS混合胶束作用时,芦丁7位羟基的氢解离后的阴离子与SDS共同作用于SB3-12形成混合胶束。UV-Vis吸收光谱和~1H NMR谱研究发现,在SB3-12胶束中,芦丁分子的A环位于季铵阳离子附近,B环位于两个相反电荷之间的弱极性区域。在SDS胶束中,B环位于栅栏层,而A环和二糖暴露于水相侧。在混合胶束中,随着SDS摩尔分数增加,对A环的静电吸引变弱。离子表面活性剂对两性离子表面活性剂胶束表面电荷密度的调节作用,本质上是对胶束极性区域的物理及化学性质的微调,进而实现对药物的可控增溶。     

Structural Transitions of CTAB Micelles in a Protic Ionic Liquid

Micellar solutions of hexadecyltrimethylammonium bromide (CTAB) in a protic ionic liquid, ethylammonium nitrate (EAN), are studied by shear rheology, polarizing optical microscopy (POM), conductivity measurements, and small angle neutron scattering (SANS). Three concentration regimes are examined: A dilute regime (with concentrations [CTAB] < 5 wt %) consisting of noninteracting spherical micelles, a semidilute regime (5 wt % ≤ [CTAB] ≤ 45 wt %) where micelles interact via electrostatic repulsions, and a concentrated regime (45 wt % < [CTAB] ≤ 62 wt %) where a reversible, temperature-dependent isotropic (L(1)) to hexatic (Hex) phase transition is observed. The L(1)-Hex transition, which has been predicted but not previously observed, is characterized by (1) a sharp increase in the shear viscosity, (2) the formation of focal conical birefringence textures (observed by POM), and (3) enhancement of the crystalline order, evidenced by the appearance of Bragg reflections in the SANS profiles. Ionic conductivity is not sensitive to the L(1)-Hex transition, which corroborates the absence of topological transitions.     

Rheology and microstructure studies of SDS/CTAB/H2O system

Phase behavior of mixed sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) aqueous solution was studied. The rheological properties and microstructure were investigated using a rheostat and freeze-fracture technique and are shown to be closely related to the phase behavior. Experimental investigations reveal two symmetrical aqueous two-phase systems (ATPS) in the ternary phase diagram of SDS/CTAB/H₂O system. In the surfactant rich phase of ATPS or in the adjacent stoichiometric state of ATPS, the system has high viscosity because of its long range ordered structure. Lamellar phase was found in the high viscosity samples in which the cationic and anionic surfactant are in 1: 3 or 3: 1 stoichiometry. In addition, the viscosity has a tendency to increase when salt was added to the solution. The viscosity increase is due to the salt can screen the repulsion between different charged headgroups and thus reduces the effective size of surfactants and facilitates the spherical or rod likes micelles to be transformed to worm-like micelles which can form hexagonal or liquid crystal phases. Large-size salt ions like sodium sulfate (especially organic salt ions) have more significant effect on the surfactant solution viscosity. The text was submitted by the authors in English.     

NMR investigations of self-aggregation characteristics of SDS in a model assembled tri-block copolymer solution

The present work was undertaken with a view to understand the influence of a model non-ionic tri-block copolymer PEO-PPO-PEO (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)) with molecular weight 5800 i.e., P123 [(EO)(20)-(PO)(70)-(EO)(20)] on the self-aggregation characteristics of the anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution (D(2)O) using NMR chemical shift, self-diffusion and nuclear spin-relaxation as suitable experimental probes. In addition, polymer diffusion has been monitored as a function of SDS concentration. The concentration-dependent chemical shift, diffusion data and relaxation data indicated the significant interaction of polymeric micelles with SDS monomers and micelles at lower and intermediate concentrations of SDS, whereas the weak interaction of the polymer with SDS micelles at higher concentrations of SDS. It has been observed that SDS starts aggregating on the polymer at a lower concentration i.e., critical aggregation concentration (cac=1.94 mM) compared to polymer-free situation, and the onset of secondary micelle concentration (C(2)=27.16 mM) points out the saturation of the 0.2 wt% polymer or free SDS monomers/micelles at higher concentrations of SDS. It has also been observed that the parameter cac is almost independent in the polymer concentrations of study. The TMS (tetramethylsilane) has been used as a solubilizate to measure the bound diffusion coefficient of SDS-polymer mixed system. The self-diffusion data were analyzed using two-site exchange model and the obtained information on aggregation dynamics was commensurate with that inferred from chemical shift and relaxation data. The information on slow motions of polymer-SDS system was also extracted using spin-spin and spin-lattice relaxation rate measurements. The relaxation data points out the disintegration of polymer network at higher concentrations of SDS. The present NMR investigations have been well corroborated by surface tension and conductivity measurements.