Oppositely Charged Surfactant Research Articles

Control of the Colloidal and Adsorption Behaviors of Chitin Nanocrystals and an Oppositely Charged Surfactant at Solid, Liquid, and Gas Interfaces.

Chitin has a unique hierarchical structure, spanning the macro- and nanoscales, and presents chemical characteristics that make it a suitable component of multiphase systems. Herein, we elucidate the colloidal interactions between partially deacetylated chitin nanocrystals (cationic ChNC) and an anionic surfactant, sodium dodecyl sulfate (SDS). We investigate charge neutralization and association (electrophoretic mobility, surface tensiometry, and quartz crystal microgravimetry) and their role in the stabilization of Pickering emulsions. We find SDS adsorption and association with ChNC under distinctive regimes: At low SDS concentration, submonolayer assemblies form on ChNC, driven by the hydrophobic effect and electrostatic interactions. With the increased SDS concentration, bilayers or patchy bilayers form, followed by adsorbed hemimicelles and micelles. We further suggested the role of hydrophobic effects in the observed colloidal transitions and complex conformations. At the highest SDS concentration tested, charge neutralization and SDS/ChNC flocculation take place. Remarkably, at given concentrations, adsorbed SDS endows the chitin nanoparticles with an effective hydrophobicity that opens the opportunity to achieve tailorable Pickering stabilization. Hence, a facile route is proposed by in situ modification by SDS physisorption, which extends the potential of renewable nanoparticles in the formulation of complex fluids, for instance, those relevant to household and healthcare products.

Aggregation and Rheology of a Triblock Supra-amphiphilic Polymer Prepared by Ionic Self-Assembly of a Double-Hydrophilic Polyelectrolyte with an Oppositely Charged Surfactant in Aqueous Solution

Aggregation and Rheology of a Triblock Supra-amphiphilic Polymer Prepared by Ionic Self-Assembly of a Double-Hydrophilic Polyelectrolyte with an Oppositely Charged Surfactant in Aqueous Solution

Nanocomposites Prepared from Carbon Nanotubes and the Transition Metal Dichalcogenides WS2 and MoS2 via Surfactant-Assisted Dispersions as Electrocatalysts for Oxygen Reactions.

Fuel cells are emerging devices as clean and renewable energy sources, provided their efficiency is increased. In this work, we prepared nanocomposites based on multiwalled carbon nanotubes (MWNTs) and transition metal dichalcogenides (TMDs), namely WS2 and MoS2, and evaluated their performance as electrocatalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR), relevant to fuel cells. The one- and two-dimensional (1D and 2D) building blocks were initially exfoliated and non-covalently functionalized by surfactants of opposite charge in aqueous media (tetradecyltrimethylammonium bromide, TTAB, for the nanotubes and sodium cholate, SC, for the dichalcogenides), and thereafter, the three-dimensional (3D) MoS2@MWNT and WS2@MWNT composites were assembled via surfactant-mediated electrostatic interactions. The nanocomposites were characterized by scanning electron microscopy (SEM) and structural differences were found. WS2@MWNT and MoS2@MWNT show moderate ORR performance with potential onsets of 0.71 and 0.73 V vs. RHE respectively, and diffusion-limiting current densities of −1.87 and −2.74 mA·cm−2, respectively. Both materials present, however, better tolerance to methanol crossover when compared to Pt/C and good stability. Regarding OER performance, MoS2@MWNT exhibits promising results, with η10 and jmax of 0.55 V and 17.96 mA·cm−2, respectively. The fabrication method presented here is cost-effective, robust and versatile, opening the doors for the optimization of electrocatalysts’ performance.

On the Thermodynamics of Micellizationof Oppositely Charged Surfactants in the Presence of Organic Additives in the Aqueous Medium

Abstract To investigate the effect of additives urea and thiourea, on the micellization behavior of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), detailed conductance measurements were carried out in aqueous media at different temperatures. The critical micelle concentration (CMC), determined from the discontinuity in the plots of molar conductance versus square root of concentration, indicated an inhibitory effect of urea and thiourea on micelle forming ability of the surfactants SDS and CTAB in the range of composition studied. The demicellizing effect of urea has been found to be more pronounced in SDS than CTAB. These observations are further augmented by the evaluation of thermodynamic parameters of micellization. A negative change in enthalpy of micellization ( Δ H m ∘ $\Delta{\text{H}}_{\text{m}}^{\circ}$ ) indicates a strong interaction between water and the additives and a positive change observed in entropy of micellization ( Δ S m ∘ $\Delta{\text{S}}_{\text{m}}^{\circ}$ ) manifest, that the micellization is an entropy-driven process. Further Δ H m ∘ $\Delta{\text{H}}_{\text{m}}^{\circ}$ and Δ S m ∘ $\Delta{\text{S}}_{\text{m}}^{\circ}$ change in mutually compensating manner, so that Δ G m ∘ < 0 $\Delta{\text{G}}_{\text{m}}^{\circ} < 0$ is not significantly affected. Finally, the counterion binding values (β) obtained for SDS and CTAB remain practically constant from 0.6 to 0.8 between 25 °C and 45 °C indicate that the size and shape of micelle remain essentially constant. Moreover, the increase in Δ G II ∘ $\Delta{\text{G}}_{{\text{II}}}^{\circ}$ values, which represent the effect of co-solvent or additive on micellization, substantiates the above observations. Many early works has investigated the micellization behavior of surfactants using a fixed additive composition. However, in this study, variable aqueous compositions of urea (0.30–1.78 wt%) and thiourea (0.24–1.41 wt%) have been considered.

Creation of New Functions by Combination of Surfactant and Polymer - Complex Coacervation with Oppositely Charged Polymer and Surfactant for Shampoo and Body Wash.

The combination of polymers and surfactants is an important means to create various functions in recent detergents and personal care products. In particular, detergents mixing oppositely charged anionic surfactants and cationic polymers induce coacervation by the dilution of the washing and rinsing process, and the complexes effectively adsorb onto surfaces and can change their characteristics. The driving force of the coacervation is electrostatic interaction between the anionic groups of the surfactant and the cationic groups of the polymer. Normally, the coacervation is controlled by selecting the molecular structure or the amount of polymer and surfactant. In shampoo and body wash compositions, we studied the complex precipitation (CP) regions and the morphology and rheological properties of precipitated complexes by focusing on the number of ionic groups in the anionic surfactants and cationic polymers, the mixed electrolyte and the ionic strength as a whole. This clarified the factors related to complex functions. For coacervation in shampoo based on alkyl ethoxylate sulfate (AES), the degree of cationization of the cationic cellulose (CC) and coexisting electrolyte greatly contributed to these functions. In a combination of moderately cationically charged CC and AES mixed amphoteric surfactant, the precipitated complexes became a loose mesh-like morphology, which was also formed when the charge shielding effect was enhanced by adding electrolyte. The precipitated complexes with a looser mesh-like morphology gave a smooth texture to the hair surface during rinsing.On the other hand, for coacervation in body wash based on fatty acid salt, the complexes were effectively precipitated in a combination with a synthetic polymer, poly diallyldimethylammonium chloride (PDADMAC), which has a higher cationic charge than CC. The precipitated complexes had high adsorbability onto skin and contributed to a moisturizing effect by lowering transepidermal water loss (TEWL).In this review, we introduce the controllable factors of coacervation in shampoo and body wash systems by focusing on the relationship between dilution processes and precipitation behavior.

Synergistic effect of like and opposite charged nanoparticle and surfactant on foam stability and mobility in the absence and presence of hydrocarbon: A comparative study

The aim of this study is to compare the synergistic impact of like and opposite-charged nanoparticle and surfactant systems on enhancing stability and mobility of foam in the absence and presence of oil which is not sufficiently discussed in the available literature. Stability of nanoparticle dispersion is examined at various levels of pH when nanoparticle and surfactant are in like and opposite-charged conditions. In situ modification of silica nanoparticle by opposite-charged surfactant is analyzed. Static stability tests as well as Hele–Shaw cell are employed to understand how nanoparticle and surfactant charges may control the stability and mobility of foam when oil is present/absent. The results indicate that surface properties of negative-charged silica nanoparticle can be modified by positive-charged surfactant. However, no modification is made on nanoparticle by surfactant carrying the same charge. Although, the mixture of like-charged nanoparticle and surfactant gives a slightly better static stability than the other one in both presence and absence of oil, both foams are not adequately able to resist oil destroying effects. When oil is absent, mobility of foam stabilized by like-charged particle and surfactant is lower. Addition of nanoparticle to the solution of same-charged surfactant increases foam apparent viscosity steadily, whereas in the case of opposite-charged surfactant solution, apparent viscosity increases at first, and then decreases by nanoparticle concentration. In the presence of oil, less mobile foam is generated by mixture of opposite-charged nanoparticle and surfactant, in contrast to the case which oil is absent. In situ modified nanoparticle stabilized foam also flows with an acceptable level of apparent viscosity when foam is detrimentally affected by oil. Model of foam flow in fracture revealed that in situ surface modified nanoparticle considerably affects the resistance of foam bubbles against deformation whereas it has negligible impact on foam film liquid term in apparent viscosity. Results of this study help to better understand in what extend the synergistic effect of nanoparticle on enhancing foam stability/mobility is controlled by combination of nanoparticle and surfactant surface charges.

The inhibition of methane hydrate formation by water alignment underneath surface adsorption of surfactants

Sodium dodecyl sulfate (SDS) has been widely shown to strongly promote the formation of methane hydrate. Here we show that SDS displays an extraordinary inhibition effect on methane hydrate formation when the surfactant is used in sub-millimolar concentration (around 0.3mM). We have also employed Sum Frequency Generation vibrational spectroscopy (SFG) and molecular dynamics simulation (MDS) to elucidate the molecular mechanism of this inhibition. The SFG and MDS results revealed a strong alignment of water molecules underneath surface adsorption of SDS in its sub-millimolar solution. Interestingly, both the alignment of water and the inhibition effect (in 0.3mM SDS solution) went vanishing when an oppositely-charged surfactant (tetra-n-butylammonium bromide, TBAB) was suitably added to produce a mixed solution of 0.3mM SDS and 3.6mM TBAB. Combining structural and kinetic results, we pointed out that the alignment of water underneath surface adsorption of dodecyl sulfate (DS−) anions gave rise to the unexpected inhibition of methane hydration formation in sub-millimolar solution of SDS. The adoption of TBAB mitigated the SDS-induced electrostatic field at the solution’s surface and, therefore, weakened the alignment of interfacial water which, in turn, erased the inhibition effect. We discussed this finding using the concept of activation energy of the interfacial formation of gas hydrate. The main finding of this work is to reveal the interplay of interfacial water in governing gas hydrate formation which sheds light on a universal molecular-scale understanding of the influence of surfactants on gas hydrate formation.

Effect of the Charge Regulation Behavior of Polyelectrolytes on Their Nonequilibrium Complexation with Oppositely Charged Surfactants.

The nonequilibrium features of oppositely charged macromolecule/surfactant mixtures have been the subject of intensive research recently. Although the nature and extent of polyion charge crucially affect the development of trapped states in these systems, their role in the nonequilibrium association is still poorly understood. In the present study, the impact of mixing on the complexation of hexadecyltrimethylammonium bromide (CTAB) with sodium poly[(vinyl alcohol)-co-(vinyl sulfate)] (PVAS) and poly(acrylic acid) (PAA) samples of similar charge densities has been compared using a variety of experimental methods. The results indicate largely different nonequilibrium behavior depending on the polyions. In the case of the weak polyacid PAA, the binding of CTAB increases its ionization degree, which leads to enhanced equilibrium two-phase concentration range, where kinetically arrested states can be observed upon rapid mixing of the solution components. In contrast, the charge density of the double-hydrophilic PVAS copolymer is fixed, and in addition to the binding of CTAB onto its vinyl sulfate groups, the surfactant molecules also bind onto the vinyl alcohol segments of the copolymer. These factors result in reduced precipitation concentration range and diminishing nonequilibrium effects with decreasing polyion charge density. Our study clearly demonstrates that the charge regulation behavior of various polyelectrolytes can be successfully used to tune the nonequilibrium characteristics of macromolecule/surfactant association.

Catanionic surfactant systems—thermodynamic and structural conditions revisited

In this work, we review shortly the current state of knowledge about catanionic surfactant systems with a focus on the detailed understanding based on the molecular buildup of such systems and of the electrostatic interaction that controls their amphiphilic monolayer and bilayer. Particularly relevant here is the extent of hydrophobicity of the oppositely charged partners, which can range from just having a more or less hydrophobic counterion until a real surfactant of opposite charge. Based on this discussion, we then investigate different systems based on cetyltrimethylammonium (CTA) combined with either laurate (L) as an oppositely charged surfactant or naphthalenesulfonate (NS) as a strongly hydrophobic counterion. Both systems were studied for the case of having salt present by combining the two amphiphilic salts but also the salt-free situation which arises from combining the hydroxide with the acid. The phase behavior was determined as well as the mesoscopic structures present, as obtained by small-angle neutron scattering (SANS) and light scattering, which allow to discern formation of wormlike micelles and vesicles. Their presence was then further confirmed by rheological measurements, where in particular normal forces allow to distinguish the two types of aggregates, and control of rheology is a key property in such systems. In addition, the thermodynamic conditions in these systems were determined by means of differential scanning calorimetry (DSC). Based on these results, a consistent understanding of the formed structures and their macroscopic properties that arise from the molecular conditions in these systems is presented.

Rheological Study of Interactions between Anionic Guar and Oppositely Charged Surfactant

We have studied the interactions between anionic carboxymethyl guar (CMG) and oppositely charged surfactant: dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB), and gemini surfactants (16-4-16), using rheological measurements. In the present study, two competing forces, electrostatic interaction and hydrophobic interaction, have been identified as important factors. Various types of structure formed on the anionic CMG chains are qualitatively discussed in comparison. For example, C12TAB and gemini surfactant tend to form polymer-bound aggregates, whereas the C16TAB tend to form the polymer-associated architecture. Furthermore, possible mechanisms based on the experimental results to elucidate these interesting phenomena have been proposed and discussed.

Effect of the Hydrophilic Head Group Size of Surfactant on the Mixed Systems of Oppositely Charged Surfactants

Effect of the Hydrophilic Head Group Size of Surfactant on the Mixed Systems of Oppositely Charged Surfactants

Theory of Collapse and Overcharging of a Polyelectrolyte Microgel Induced by an Oppositely Charged Surfactant

We report on the theoretical study of interaction of ionic surfactants with oppositely charged microgel particles in dilute solutions. Two approaches are proposed. Within the first approach, the micellization of the surfactants inside the microgel is taken into account while the second model focuses on the hydrophobic interactions of the surfactant tails with the hydrophobic parts of microgel subchains. It has been shown that microgels effectively absorb surfactant ions. At low surfactant concentration this absorption is realized due to an ion exchange between microgel counterions and surfactant ions. The ion exchange is significantly affected by the amount of the microgel counterions initially trapped within the microgel particles which depends on the size of the microgel, its ionization degree, cross-linking density as well as polymer concentration in the solution. Increase of the surfactant concentration causes contraction of the microgels, which can be realized as either a continuous shrinking or a ju...

Strong cooperative effect of oppositely charged surfactant mixtures on their adsorption and packing at the air-water interface and interfacial water structure.

Remarkable adsorption enhancement and packing of dilute mixtures of water-soluble oppositely-charged surfactants, sodium dodecyl sulfate (SDS) and dodecyl amine hydrochloride (DAH), at the air-water interface were observed by using sum frequency generation spectroscopy and tensiometry. The interfacial water structure was also observed to be significantly influenced by the SDS-DAH mixtures, differently from the synergy of the single surfactants. Most strikingly, the obtained spectroscopic evidence suggests that the interfacial hydrophobic alkyl chains of the binary mixtures assemble differently from those of single surfactants. This study highlights the significance of the cooperative interaction between the headgroups of oppositely charged binary surfactant systems and subsequently provides some insightful observations about the molecular structure of the air-aqueous interfacial water molecules and, more importantly, about the packing nature of the surfactant hydrophobic chains of dilute SDS-DAH mixtures of concentration below 1% of the CMC.

DETERMINATION OF METHYLENE BLUE BIOSORPTION BY Rhizopus arrhizus IN THE PRESENCE OF SURFACTANTS WITH DIFFERENT CHEMICAL STRUCTURES

Methylene blue (MB) biosorption properties of Rhizopus arrhizus were investigated in the presence of surfactants. The effects of cationic and anionic surfactants on MB removal by dead biomass (1 g L−1) were determined. MB removal was tested as a function of initial pH (2–12), contact time (5–1440 min), and dye (37.4–944.7 mg L−1) and surfactant (0–10 mM) concentrations. The opposite charged anionic surfactant dodecylbenzenesulfonic acid sodium salt (DBS) enhanced sorption of cationic MB by biomass dramatically. Maximum biosorption capacity was 471.5 mg g−1 at pH 8 with 0.5 mM DBS at 944.7 mg L−1 MB concentration. The surfactant-stimulated fungal decolorization method may provide a highly efficient, inexpensive, and time-saving procedure in biological wastewater treatment technologies.

Cationic oligo- p-phenylene ethynylenes form complexes with surfactants for long-term light-activated biocidal applications

Cationic oligo-p-phenylene ethynylenes are highly effective light-activated biocides that deal broad-spectrum damage to a variety of pathogens, including bacteria. A potential problem arising in the long-term usage of these compounds is photochemical breakdown, which nullifies their biocidal activity. Recent work has shown that these molecules complex with oppositely-charged surfactants, and that the resulting complexes are protected from photodegradation. In this manuscript, we determine the biocidal activity of an oligomer and a complex formed between it and sodium dodecyl sulfate. The complexes are able to withstand prolonged periods of irradiation, continuing to effectively kill both Gram-negative and Gram-positive bacteria, while the oligomer by itself loses its biocidal effectiveness quickly in the presence of light. In addition, damage and stress responses induced by these biocides in both E. coli and S. aureus are discussed. This work shows that complexation with surfactants is a viable method for long-term light-activated biocidal applications.

Mixtures of latex particles and the surfactant of opposite charge used as interface stabilizers--influence of particle contact angle, zeta potential, flocculation and shear energy.

We investigate the stabilization of air-water interfaces by mixtures of negatively charged latex particles (sulfate polystyrene) and cationic surfactants (alkyl trimethylammonium bromides). First we report results concerning the binding of surfactant molecules to the latex particles. As the surfactant concentration increases, the charge of the particles reverses, from negative to positive, because CnTAB first binds electrostatically to the latex particles and then through hydrophobic interaction with the monolayer already adsorbed on the particles as well as directly with the hydrophobic surface of the latex. Over a large range of surfactant concentrations around the charge inversion, a strong flocculation is observed and 100 μm large aggregates form in the suspension. Unlike previous studies published on mixtures of inorganic particles with oppositely charged surfactants, we show that we can vary the sign of the zeta potential of the particles without changing the contact angle of the particles over a large range of surfactant concentrations. Indeed, the latex particles that we study are more hydrophobic than inorganic particles, hence adding moderate concentrations of the surfactant results in a weak variation of the contact angle while the charge of the particles can be reversed. This enables decoupling of the effect of zeta potential and contact angle on the interfacial properties of the mixtures. Our study shows that the contact angle and the charge of the particles are not sufficient parameters to control the foam properties, and the key-parameters are the flocculation state and the shear energy applied to produce the foam. Indeed, flocculated samples, whatever the sign of the zeta potential, enable production of a stable armour at the interface. The large aggregates do not adsorb spontaneously at the interface because of their large size, however when a large shear energy is used to produce the foam very stable foam is obtained, where particles are trapped at interfaces. We suggest that the large aggregates may be broken during shear and may reform at the interface to form a solid armour. A simple calculation taking into account the adsorption dynamics of the aggregates as a function of their size is consistent with this hypothesis.

Understanding and Exploiting the Phase Behavior of Mixtures of Oppositely Charged Polymers and Surfactants in Water

Complexes of oppositely charged polymers and surfactants (OCPS) in water come in many varieties, including liquid-crystalline materials, soluble complexes, structured nanoparticles, and water-insoluble surface layers. The range of available structures and properties increases even further with the addition of other amphiphilic substances that may enter, or even dissolve, the complexes, depending on the nature of the additive. Simple operations may change the properties of OCPS systems dramatically. For instance, dilution with water can induce a phase separation in an initially stable OCPS solution. More complicated processes, involving chemical reactions, can be used to either create or disintegrate OCPS particles or surface layers. The richness of their properties has made OCPS mixtures ubiquitous in everyday household products, such as shampoos and laundry detergents, and also attractive ingredients in the design of new types of responsive particles, surfaces, and delivery agents of potential use in future applications. A challenge for the rational design of an OCPS system is, however, to obtain a good fundamental understanding of how to select molecular shapes and sizes and how to tune the hydrophobic and electrostatic interactions such that the desired properties are obtained. Recent studies of OCPS phase equilibria, using a strategy where the minimum number of components is always used to address a particular question, have brought out general rules and trends that can be used for such a rational design. Those fundamental studies are reviewed here, together with more application-oriented studies where fundamental learning has been put to use.

Electrostatic Interactions and Aqueous Two-Phase Separation Modes of Aqueous Mixed Oppositely Charged Surfactants System

Electrostatic interactions play an important role in setting the aqueous two-phase separation behaviors of mixtures of oppositely charged surfactants. The aqueous mixture of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfonate (AS) is actually a five-component system, comprised of CTAB, AS, complex salt (cetyltrimethylammonium dodecylsulfonate, abbreviated as CTA(+)AS(-)), NaBr, and water. In the three-dimensional pyramid phase diagram, the aqueous two-phase region with excess AS or with excess CTAB extends successively from the region very near to the NaBr-H2O line through the CTAB-AS-H2O conventional mixing plane to the CTA(+)AS(-)-AS-H2O side plane or to the CTA(+)AS(-)-CTAB-H2O side plane, respectively. Large or small molar ratios between the counterions and their corresponding surfactant ions for oppositely charged surfactants located in the NaBr side or the CTA(+)AS(-) side of the pyramid imply strong or weak electrostatic screening. Electrostatic screening of counterions alters the electrostatic attractions between the oppositely charged head groups or the electrostatic repulsions between the like-charged head groups in excess, and the electrostatic free energy of aggregation thus affects the aqueous two-phase separation modes. Composition analysis, rheological property investigation, and TEM images suggest that there are two kinds of aqueous two-phase systems (ATPSs). On the basis of these experimental results and Kaler's cell model, two kinds of phase separation modes were proposed. Experimental results also indicate that all of the top phases are surfactant-rich, and all of the bottom phases are surfactant-poor; the density difference between the top phase and the bottom phase in one ATPS is very small; the interfacial tension (σ) of the ATPS is ultralow.

Self-Aggregation of Mixtures of Oppositely Charged Polyelectrolytes and Surfactants Studied by Rheology, Dynamic Light Scattering and Small-Angle Neutron Scattering

In this study, the phase behavior, structure and properties of systems composed of the cationic, cellulose-based polycation JR 400 and the anionic surfactants sodium dodecylbenzenesulfonate (SDBS) or sodium dodecylethoxysulfate (SDES), mainly in the semidilute regime, were examined. This system shows the interesting feature of a very large viscosity increase by nearly 4 orders of magnitude as compared to the pure polymer solution already at very low concentrations of 1 wt%. By using rheology, dynamic light scattering (DLS), and small-angle neutron scattering (SANS), we are able to deduce systematic correlations between the molecular composition of the systems (characterized by the charge ratio Z=[+(polymer)]/[−(surfactant)]), their structural organization and the resulting macroscopic flow behavior. Mixtures in the semidilute regime with an excess of polycation charge form highly viscous network structures containing rodlike aggregates composed of surfactant and polyelectrolyte that are interconnected by the long JR 400 chains. Viscosity and storage modulus follow scaling laws as a function of surfactant concentration (η~c(s)(4); G(0)~c(s)(1.5)) and the very pronounced viscosity increase mainly arises from the strongly enhanced structural relaxation time of the systems. In contrast, mixtures with excess surfactant charges form solutions with viscosities even below those of the pure polymer solution. The combination of SANS, DLS, and rheology shows that the structural, dynamical, and rheological properties of these oppositely charged polyelectrolyte/surfactant systems can be controlled in a systematic fashion by appropriately choosing the systems composition.

Rheological Behavior of Aqueous Solutions of Cationic Guar in Presence of Oppositely Charged Surfactant

The cationic guar (CG) is synthesized and the rheological behavior of aqueous solutions of CG in the presence of sodium dodecyl sulfate (SDS) is studied in detail. The steady viscosity measurements show that the zero shear viscosity enhancement can be almost 3 orders of magnitude as the concentration of SDS increases from 0 to 0.043%. The gel-like formation is observed as the concentration of SDS is greater than 0.016%. The oscillatory rheological measurements of CG solutions in the presence of SDS show that the crossover modulus is almost independent of the concentration of SDS whereas the apparent relaxation time increases swiftly upon increasing the concentration of SDS. The experimental results indicate that the strength rather than the number of the cross-links is greatly affected by SDS molecules. The mechanism concerning the effect of SDS upon the rheology of CG solutions can be coined by the two-stage model. Before the formation of cross-links at the critical concentration, the electrostatic interaction between SDS and cationic site of CG chains plays a key role and the SDS molecules bind to CG chains through the electrostatic interaction. After the formation of cross-links at the concentration greater than the critical concentration, the cooperative hydrophobic interaction become dominant and SDS molecules bind to the cross-links through the hydrophobic interaction. The rheological behavior of aqueous solutions of CG in the presence of SDS is chiefly determined by the micelle-like cross-links between CG chains. In fact, the flow activation energy of CG solution, obtained from the temperature dependence of the apparent relaxation time, falls in the range of transferring a hydrophobic tail of SDS from the micelle to an aqueous environment.