Rheological properties of viscoelastic surfactant systems

Rehage, Heinz; Hoffmann, H.

doi:10.1021/j100327a031

Cited by 681 publications

(591 citation statements)

References 4 publications

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“…On the other hand, the slope of the power-law region of flow curves for some dilute worm-like micelles (i.e. long and flexible cylinders) of cationic surfactants/water systems [18,19] was found to be ca. 0.89.…”

Section: Micellar Phasementioning

confidence: 99%

Shear rheology and phase behaviour of sodium oleate/water mixtures

Antunes

Coppola

Gaudio

et al. 2007

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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The knowledge of structural and dynamical properties in binary sodium oleate (NaO)/water mixtures represents a first step for studying new biocompatible structures. In addition, a deeper understanding of their flow behaviour is crucial to control their mechanical properties. The purpose of this investigation was to revisit the binary NaO/water phase diagram through a combined effort of shear-rheology, NMR-diffusometry, optical polarizing microscopy and differential scanning calorimetry. The preparation of NaO/water mixtures in this work fitted with the interesting regions of the phase diagrams where most of the new systems will be prepared (i.e. from 0.01 to 30 wt.% NaO and within the temperature range 5-70 • C).Steady shear and linear viscoelastic experiments were accurately performed and the relationship between phase morphology and rheological properties was also studied. Regarding the mixtures at low surfactant concentrations, the shear flow showed: (1) a structural evolution into the liquid micellar phase (L 1 ) as a function of composition and (2) the presence of a viscous micellar region (L * 1 ) induced by temperature and composition changes. NaO/water mixtures with a liquid-crystalline structure (hexagonal H 1 ) were studied by linear shear deformations and paying particular attention to frequency and temperature scans. Viscoelastic spectra of H 1 phase presented a gel-like response which, although not expected, indicated the presence of a stiff liquid-crystalline lattice. Finally, a correlation between rheology and microstructural changes was conducted by the "weak-gel" model.

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Section: Micellar Phasementioning

confidence: 99%

Shear rheology and phase behaviour of sodium oleate/water mixtures

Antunes

Coppola

Gaudio

et al. 2007

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…Since the pioneering work of Rehage and Hoffman [41], CPCl/NaSal is known to self-assemble spontaneously into micrometer long wormlike micelles. The surfactant solution was prepared at = 2 .…”

Section: -Wormlike Micellar Solutions and Linear Rheologymentioning

confidence: 99%

Magnetic wire-based sensors for the microrheology of complex fluids

et al. 2013

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Abstract:We propose a simple µ-rheology technique to evaluate the viscoelastic properties of complex fluids. The method is based on the use of magnetic wires of a few microns in length submitted to a rotational magnetic field. In this work, the method is implemented on a surfactant wormlike micellar solution that behaves as an ideal Maxwell fluid. With increasing frequency, the wires undergo a transition between a steady and a hindered rotation regime. The study shows that the average rotational velocity and the amplitudes of the oscillations obey scaling laws with well-defined exponents. From a comparison between model predictions and experiments, the rheological parameters of the fluid are determined. -IntroductionRheology is the study of flow and deformation of fluids when they are submitted to mechanical stresses. Conventional rheometers determine the relationship between strain and stress in steady or oscillating flow on samples of a few milliliters. µ-rheology in contrast studies the motion of micron-size probe particles that are thermally fluctuating via the interactions with a surrounding medium, or particles that are forced by an external field. In the first case, the µ-rheology is said to be passive, in the second active. In both cases, the motion of the probes is related by the mechanical properties of the medium. Fluids produced in small quantities, e.g. costly protein dispersion or fluids confined in small volumes down to 1 picoliter, such as living cells can only be examined by this technique. With the development of microfluidics systems in the last decade [1], rapid advances were made in the field of µ-rheology. Standard experimental protocols and data treatment softwares are now available and implemented on a regular and controlled basis [2][3][4][5][6][7]. The correspondence between µ-and macro-rheology is nowadays well established. In µ-rheology, the objective is to translate the motion of a probe particle into the relevant rheological

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“…Flow-induced structure formation has been reported in solutions of wormlike micelles; however, until now, these structures were all temporary and would disintegrate on cessation of the flow (22,23,25,26,36). These transient structures were first reported by Rehage and Hoffmann (36), who found that a wormlike micellar solution, an aqueous solution of the cationic surfactant cetylpyridinium chloride ([CPyCl] = 15-100 mM) and the organic salt sodium salicylate ([NaSal] = 11-60 mM), form a gel-like structure under shear flow above a critical shear rate.…”

Section: Flow-induced Structuresmentioning

confidence: 99%

Microstructure and rheology of a flow-induced structured phase in wormlike micellar solutions

Cardiel

Dohnálková

Dubash

et al. 2013

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

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Surfactant molecules can self-assemble into various morphologies under proper combinations of ionic strength, temperature, and flow conditions. At equilibrium, wormlike micelles can transition from entangled to branched and multiconnected structures with increasing salt concentration. Under certain flow conditions, micellar structural transitions follow different trajectories. In this work, we consider the flow of two semidilute wormlike micellar solutions through microposts, focusing on their microstructural and rheological evolutions. Both solutions contain cetyltrimethylammonium bromide and sodium salicylate. One is weakly viscoelastic and shear thickening, whereas the other is strongly viscoelastic and shear thinning. When subjected to strain rates of ∼10 3 s −1 and strains of ∼10 3 , we observe the formation of a stable flow-induced structured phase (FISP), with entangled, branched, and multiconnected micellar bundles, as evidenced by electron microscopy. The high stretching and flow alignment in the microposts enhance the flexibility and lower the bending modulus of the wormlike micelles. As flexible micelles flow through the microposts, it becomes energetically favorable to minimize the number of end caps while concurrently promoting the formation of cross-links. The presence of spatial confinement and extensional flow also enhances entropic fluctuations, lowering the energy barrier between states, thus increasing transition frequencies between states and enabling FISP formation. Whereas the rheological properties (zero-shear viscosity, plateau modulus, and stress relaxation time) of the shear-thickening precursor are smaller than those of the FISP, those of the shear-thinning precursor are several times larger than those of the FISP. This rheological property variation stems from differences in the structural evolution from the precursor to the FISP. microfluidics | microrheology | mesh size S urfactant molecules in aqueous solutions can self-assemble into different structures, such as spherical micelles, cylindrical micelles, lamellar phases, and vesicles (1). The morphology of these self-assembled structures is influenced by surfactant concentration, temperature, external additives (e.g., cosurfactants or salts), and flow conditions. Cylindrical micelles in the presence of inorganic or organic salts can self-assemble into large, flexible, and elongated wormlike micelles that exhibit viscoelastic properties (2-4). The ionic strength of the salt screens the electrostatic repulsions between the charged surfactant head groups, promoting cylindrical micellar growth (1-3). At higher salt concentrations, the entangled linear micelles can transition to branched and multiconnected micellar networks, as evidenced by rheological measurements, light scattering techniques, and electron microcopy (EM) imaging (5-18). Additionally, wormlike micellar solutions are known to exhibit a variety of interesting phenomena, some of which are shear banding (19-21), shear thickening (22, 23), shear-induced transitions and insta...

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Rheological properties of viscoelastic surfactant systems

Cited by 681 publications

References 4 publications

Shear rheology and phase behaviour of sodium oleate/water mixtures

Shear rheology and phase behaviour of sodium oleate/water mixtures

Magnetic wire-based sensors for the microrheology of complex fluids

Microstructure and rheology of a flow-induced structured phase in wormlike micellar solutions

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