Flow Birefringence Measurements on Viscoelastic Surfactant Solutions

Löbl, M.; Thurn, H.; Hoffmann, H.

doi:10.1002/bbpc.198400015

Cited by 34 publications

(12 citation statements)

References 19 publications

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“…Similar behaviour have been observed for simpler cationic surfactants, mostly single chained N-cationic surfactants, some time ago [5][6][7]. Moreover, this uni-dimensional growth is favored by an appropriate choice of the surfactant and inorganic salt concentrations, so the micelles can become very long rod-like aggregates, which can be either be flexible and resemble those of polymer molecules [8][9][10][11][12][13][14], or indeed very stiff rods which are considerable larger than the persistence length (on a length scale) as noticed for SLES at high inorganic salt concentrations of the order of 0.5 M NaCl [3,15]. Organic counterions behave differently depending on the chemical structure, chirality and intrinsic surface activity, respectively [16].…”

Section: Introductionsupporting

confidence: 60%

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Dynamic Properties of Entangled Wormlike Micelles: Sodium Laurylethersulfate at High Ionic Strength-(II)

Clancy¹,

Fuller²,

Scheidt³

et al. 2001

Zeitschrift Für Physikalische Chemie

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Entanglement / Sodium Laurylethersulfate / Wormlike Micelles / Rheology / Light Scattering / ViscoelasticityWe report on the viscous behaviour of long and flexible wormlike micelles at volume fractions between ? = 0.05-0.14 comprised of sodium laurylethersulfate (SLES) in 0.15-0.5 M NaCl equivalent of SLES concentrations between 20-50 mM at temperatures ranging from 25 • C to 45 • C by means of static and dynamic light scattering and rheology, which is an extension of previous experiments on dilute/semi-dilute solutions of SLES micelles at much lower surfactant concentrations in the presence of low salt concentrations (Clancy and Paradies, Z. Phys. Chem. 215, 4, 483-513 (2001)). The light scattering results lead to a description of the solution of wormlike SLES micelles as analogous to semidilute solutions of living polymers in good solvents. The dynamic properties of SLES micelles as shown by the time autocorrelation function of the scattered field was found to be bimodal, particularly between 0.15-0.5 M NaCl (25 • C). The origin and the influence of surfactant concentration and salt concentration of the bimodal behaviour are investigated in more detail and compared to theoretical models describing coupling of concentration fluctuations to viscoelasticity. Specifically the behaviour of the slow viscoelastic time as a function of temperature, salt, and SLES concentration has been extensively evaluated experimentally and compared with theoretical predictions, revealing that the terminal stress relaxation time obtained from inelastic light scattering measurements is in accord with the rheological experiments. Above the crossover concentration of SLES of ?* ∼ = 0.06 the viscoelastic properties are described by an almost ideal Maxwell relaxation. The overall rheological data are in agreement with the scaling law with respect to surfactant concentration with exponents close to those predicted from a stress relaxation model applying living polymers. Furthermore, the complex elastic modulus at higher angle frequency obtained can be explained in terms of crossover between the regimes of reversible scission, and of breathing of the polymer-like SLES chains. The average increase of the chain length (L) with increasing SLES concentration in the presence of 0.15-0.5 M NaCl at 25 • C scales with ∼ = ? 0.31−0.34 according to static light scattering measurements. The hydrodynamic correlation length, ξ H , obtained from inelastic light scattering experiments is best approximated by ξ H ≈ C −0.78 , whereas the correlation length ξ c scales with C −0.48 , which is a significant smaller exponent than predicted of −0.75 theoretically. -The rheological and dynamical behaviour of SLES micelles studied in this concentration range, e.g. the transition between dilute to semi-dilute regimes, including gelation shows the very different physical properties of SLES than that of its non-ethoxylated analogue and well studied sodium dodecylsulfate (SDS).

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Section: Introductionsupporting

confidence: 60%

“…2 and 3) the SLES chains are well separated from each other, and the correlation lengths can be estimated as ∼ = R G /(3) 1/2 according to Eqs. (12) and (13). The values found are ξ c = 528 Å and ξ H = 531 Å, respectively at 25 • C. Both correlation lengths vary with temperature between 25 • C and 45 • C, e.g.…”

Section: 2mentioning

confidence: 88%

Dynamic Properties of Entangled Wormlike Micelles: Sodium Laurylethersulfate at High Ionic Strength-(II)

Clancy¹,

Fuller²,

Scheidt³

et al. 2001

Zeitschrift Für Physikalische Chemie

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“…No birefringence is observed at the start of the applied shear; it only builds up during shear. The results of all these Couette flow measurements indicate the growth of shear induced structures consisting of anisometric particles which are practically completely aligned in the flow direction as can be seen from the extinction angle 2/ [23], which is …”

Section: Flow Birq/hngence In Couette Flowmentioning

confidence: 79%

“…The flow birefringence measurements were performed using an apparatus described elsewhere [23]. The turbulent flow measurement were carried out in two different systems in which the solution were continuously pumped around a closed circuit.…”

Section: Measuring Equipmentmentioning

confidence: 99%

Surfactant systems for drag reduction: Physico-chemical properties and rheological behaviour

1986

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The first part of the work presents an overview of the physical chemistry of surfactants which in aqueous solutions reduce the frictional loss in turbulent pipe flow. It is shown that these surfactants form rodlike micelles above a characteristic concentraion c t. The experimental evidence for rodlike micelles are reviewed and the prerequisites that the surfactant system must fulfill in order to form rodlike micelles are given. It is demonstrated by electrical conductivity measurements that the critical concentration for the formation of spherical micelles shows little temperature dependence, whereas ct increases very rapidly with temperature. The length of the rodlike micelles, as determined by electric birefringence, decreases with rising temperature and increases with rising surfactant concentration. The dynamic processes in these micellar systems at rest and the influence of additives such as electrolytes and short chain alcohols are discussed.In the second part, the rheological behaviour of these surfactant solutions under laminar and turbulent flow conditions are investigated. Viscosity measurements in laminar pipe and Couette flow show the build-up of a shear induced viscoelastic state, SIS, from normal Newtonian fluid flow. A complete alignment of the rodlike micelles in the flow direction in the SIS was verified by flow birefringence. In turbulent pipe flow, drag reduction occurs in these surfactant systems as soon as rodlike micelles are present in the solution. The extent and type of drag reduction, i.e. the shape of the friction factor versus Reynolds number curve, depends directly on the size, number and surface charge of the rodlike micelles. The friction factor curve of each surfactant investigated changes in the same characteristic way as a function of temperature. For each surfactant, independent of concentration, an upper absolute temperature limit, TL, for drag reduction exists which is caused by the micellar dynamics. T L is influenced by the hydrophobic chain length and the counter-ion of the surfactant system. A first attempt is made to explain the drag reduction of surfactants by combining the results of these rheological measurements with the physico-chemical properties of the micellar systems.

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“…The addition of counterions modifies the evolution of these structures. Cationic surfactant systems of alkyl trimethyl ammonium type RTA> (like CTAB) show pronounced viscoelastic behaviour when the salicylate counterion Sal\ is present [7][8][9][10][11][12][13][14][15]. NMR spectroscopy [16] has revealed that when C , 1 4C !2 (R"C 1 /C " 41), almost all NaSal dissociate and Sal\ ions form complexes with CTA> to form thread-like micelles.…”

Section: Introductionmentioning

confidence: 99%

Occurrence of shear thickening in aqueous micellar solutions of CTAB with some added organic counterions

Hartmann¹,

Cressely²

1998

Colloid & Polymer Science

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V. Hartmann ) Prof. R. Cressely ( ) Laboratoire de Physique des Liquides et des interfaces Groupe Rhe´ophysique des Colloides Universite´de Metz -1Bd F. AragoAbstract In this experimental work we carefully investigate the influence of some organic counterions (having similarities): sodium salicylate (NaSal), sodium tosylate (NaTos) and sodium benzoate (NaBz) on the rheological properties of two aqueous solutions (0.1 and 0.05 M) of cetyltrimethylammonium bromide (CTAB). Here we are particularly interested in the occurrence of the shear thickening effect corresponding to shear induced structures (SIS). All the rheological measurements presented in this work are realized with the same geometrical device (plan-cone) with controlled imposed shear stress. Conditions of occurrence and evolutions of the characteristics of the obtained shear thickening are given.

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Flow Birefringence Measurements on Viscoelastic Surfactant Solutions

Cited by 34 publications

References 19 publications

Dynamic Properties of Entangled Wormlike Micelles: Sodium Laurylethersulfate at High Ionic Strength-(II)

Dynamic Properties of Entangled Wormlike Micelles: Sodium Laurylethersulfate at High Ionic Strength-(II)

Surfactant systems for drag reduction: Physico-chemical properties and rheological behaviour

Occurrence of shear thickening in aqueous micellar solutions of CTAB with some added organic counterions

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