Microstructural Changes in SDS Micelles Induced by Hydrotropic Salt

Hassan, P. A.; Raghavan, Srinivasa R.; Kaler, Eric W.

doi:10.1021/la011435i

Cited by 267 publications

(261 citation statements)

References 40 publications

Supporting

Mentioning

243

Contrasting

Order By: Relevance

“…At equilibrium, the organic counter-ion PTHC has the tendency to remain at the micelle-water interface, decreasing the spontaneous curvature of the micellar aggregates and transforming them from cylinders to bilayers (13,14). The equilibrium phase behavior of the concentrated phases was investigated recently in this system, and a novel isotropic phase ðL i Þ of bilayers was reported (15).…”

mentioning

confidence: 95%

Reversible shear-induced crystallization above equilibrium freezing temperature in a lyotropic surfactant system

Rathee

Krishnaswamy

Pal

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

We demonstrate a unique shear-induced crystallization phenomenon above the equilibrium freezing temperature ðT o K Þ in weakly swollen isotropic ðL i Þ and lamellar ðL α Þ mesophases with bilayers formed in a cationic-anionic mixed surfactant system. Synchrotron rheological X-ray diffraction study reveals the crystallization transition to be reversible under shear (i.e., on stopping the shear, the nonequilibrium crystalline phase L c melts back to the equilibrium mesophase). This is different from the shear-driven crystallization below T o K , which is irreversible. Rheological optical observations show that the growth of the crystalline phase occurs through a preordering of the L i phase to an L α phase induced by shear flow, before the nucleation of the L c phase. Shear diagram of the L i phase constructed in the parameter space of shear rate ð_ γÞ vs. temperature exhibits L i → L c and L i → L α transitions above the equilibrium crystallization temperature ðT o K Þ, in addition to the irreversible shear-driven nucleation of L c in the L i phase below T o K . In addition to revealing a unique class of nonequilibrium phase transition, the present study urges a unique approach toward understanding shear-induced phenomena in concentrated mesophases of mixed amphiphilic systems.shear-induced phase separation | strongly binding counterions | coagels S hear is known to assist crystallization below the equilibrium freezing temperature in complex fluids like colloidal glasses (1, 2), dense granular suspensions (3), polymer melts (4, 5), micellar solutions of block copolymers (6), and multicomponent surfactant systems (7,8). Shear-driven crystallization is equally relevant for simple fluids like bulk metallic glasses (9), molecular liquids (10), and atomic systems (11). The general understanding is that shear lowers the energy barrier for nucleation and accelerates the growth of a stable crystalline phase from a metastable, amorphous/ isotropic solution at Peclet number Pe = σa 3 kBT > 1, where σ is the shear stress, a is the characteristic length scale, and k B T is the thermal energy (12). The crystalline phase primarily induced by the effect of flow on the internal structure and ordering of the constituents does not revert to the starting fluid state when the imposed shear is removed, indicating that the phenomenon is not a dynamic phase transition. In the present study, we report a unique phenomenon, where under steady shear, crystallization occurs above the equilibrium crystallization temperature ðT o K Þ in an isotropic mesophase ðL i Þ consisting of bilayers formed in a lyotropic surfactant system. Notably, above T o K , when the imposed shear is removed, the crystalline phase melts back to the starting L i phase.The studies were carried out in a cationic-anionic mixed surfactant system formed by SDS and the strong binding counter-ion paratoluene hydrochloride (PTHC) in water. At equilibrium, the organic counter-ion PTHC has the tendency to remain at the micelle-water interface, decreasing the spontaneous curvat...

show abstract

mentioning

confidence: 95%

Reversible shear-induced crystallization above equilibrium freezing temperature in a lyotropic surfactant system

Rathee

Krishnaswamy

Pal

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Recently, one of us was involved in a study where we identified p-toluidine hydrochloride (PTHC) as a binding salt that could rapidly induce the growth of SDS worms. 6 One issue with using SDS to form wormlike micelles is that the zero-shear viscosity of these solutions is typically quite low (∼1 Pa‚s). This is probably related to the short (C 12 ) tail length of SDS, whereas, in comparison, popular worm-forming cationic surfactants (e.g., cetyl trimethylammonium bromide, CTAB) have 16 carbons or more in their tails.…”

Section: Introductionmentioning

confidence: 99%

Anionic Wormlike Micellar Fluids that Display Cloud Points: Rheology and Phase Behavior

2005

Self Cite

View full text Add to dashboard Cite

We report our investigations into the self-assembly of sodium oleate (NaOA) in the presence of a binding salt (triethylammonium chloride, Et 3 NHCl) simple salt (potassium chloride, KCl). Both salts promote the growth of long, wormlike micelles in NaOA solutions, thereby increasing the fluid viscosity. The significant difference with the Et 3 NHCl salt is that it also modifies the phase behavior of NaOA solutions. Specifically, NaOA/Et 3 NHCl solutions display cloud points upon heating, followed by phase separation into two liquid phases. Such cloud point behavior is rarely observed in ionic surfactant systems, although it is common in nonionic surfactant solutions. Interestingly, while cloud points are not observed with KCl, the addition of KCl to NaOA/Et 3 NHCl solutions further lowers the cloud point temperature. Also, in the case of tetraethylammonium halide salt, neither a cloud point nor an increase in viscosity is observed. The clouding in the case of Et 3 NHCl is attributed to the temperature-induced aggregation of anionic micelles whose surface is covered by bound counterions.

show abstract

“…The hydrotrope partitions into the surfactant headgroup region and results in dramatic micellar growth. Similarly, a cationic hydrotrope can drive the growth of anionic micelles [5]. As the molecular weight (or length) of the hydrophobic portion of the hydrotrope is increased, the hydrotrope begins to behave more like a second surfactant and can alter the self-assembly in solution, leading to the formation of vesicles.…”

Section: Introductionmentioning

confidence: 99%

Phase Behavior and Microstructure in Aqueous Mixtures of Cationic and Anionic Surfactants

Kaler¹,

Herrington²,

Iampietro³

et al. 2004

Surfactant Science

View full text Add to dashboard Cite

][ [Page No. 290] {Books}4380-Abe/4380-Abe-009.3d 4380-Abe SYNOPSISMixtures of anionic and cationic surfactants in water display interesting phase behavior and a range of microstructures, including small micelles, rod-like micelles, lamellar phases and vesicles. This chapter reviews the properties of these mixtures with a focus on the experimental and theoretical aspects of vesicle formation and stability.

show abstract

Microstructural Changes in SDS Micelles Induced by Hydrotropic Salt

Cited by 267 publications

References 40 publications

Reversible shear-induced crystallization above equilibrium freezing temperature in a lyotropic surfactant system

Reversible shear-induced crystallization above equilibrium freezing temperature in a lyotropic surfactant system

Anionic Wormlike Micellar Fluids that Display Cloud Points: Rheology and Phase Behavior

Phase Behavior and Microstructure in Aqueous Mixtures of Cationic and Anionic Surfactants

Contact Info

Product

Resources

About