Nonequilibrium thermodynamic modeling of the structure and rheology of concentrated wormlike micellar solutions

Germann, Natalie; Cook, L. Pamela; Beris, Antony N.

doi:10.1016/j.jnnfm.2012.12.010

Cited by 66 publications

(68 citation statements)

References 17 publications

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“…Both quantities exhibit a pronounced maximum upon variation of strain rate _ e at the same critical value. The decrease of the elongational viscosity and R G is attributed to the scission of micelles as predicted theoretically [Vasquez et al (2007); Cromer et al (2009);Germann et al (2013)]. However, it could not be resolved whether the increase in R G observed at low elongation rates is just due to alignment and elongation of micelles in flow direction or whether fusion of micelles occurs increasing the average micellar contour length [Chen and Warr (1997)].…”

Section: Elongational Flow Of Wlm Solutionsmentioning

confidence: 80%

“…Respective applications involve complex flow kinematics with strong extensional components, which can cause large and rapid deformation of the fluid microstructure. The resulting stretching and alignment of micelles lead to a range of unconventional phenomena including flow-induced chain scission [Vasquez et al (2007); Germann et al (2013)], structure formation [Vasudevan et al (2010)], and elastic instabilities [Pathak and Hudson (2006)]. A fundamental understanding of material properties as well as the ability to predict changes that occur within the material during processing is extremely important for industrial application.…”

Section: Introduction a General Remarksmentioning

confidence: 99%

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Elongational deformation of wormlike micellar solutions

Sachsenheimer

Oelschlaeger

Müller

et al. 2014

Journal of Rheology

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We have investigated the uniaxial elongation behavior of six different wormlike micelle systems covering a broad range of surfactant concentrations cs and salt/surfactant ratios R using the capillary breakup elongational rheometry (CaBER). In the fast-breaking limit (high cs and R), filament lifetime tfil is controlled by the equilibrium shear modulus G0 and the breakage time λbr obtained from small oscillatory shear according to tfil/G0∝λbr2/3 and relaxation time ratios λe/λs≈1 are found. When reptation dominates (high cs, low R) λe/λs<1 is observed similar as for solutions of covalently bound polymers. In this concentration regime, the micellar structure seems not to be affected by the strong elongational flow. In contrast, high filament lifetimes up to 1000 s and λe/λs values up to 10 are observed at low cs irrespective of R. This indicates the formation of elongation-induced structures (EISs). A minimum viscosity and a minimum initial diameter are required for creating EIS. Additional filament stretching experiments indicate that a critical total deformation has to be exceeded for structure build-up. Finally, our experiments reveal a distinct difference regarding the dependence between solutions of linear and branched micelles of filament lifetime on viscosity suggesting that CaBER is a versatile means to distinguish between these structures.

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Section: Elongational Flow Of Wlm Solutionsmentioning

confidence: 80%

Section: Introduction a General Remarksmentioning

confidence: 99%

Elongational deformation of wormlike micellar solutions

Sachsenheimer

Oelschlaeger

Müller

et al. 2014

Journal of Rheology

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show abstract

“…In shearing flow, in that same limit, the Rolie-Poly model is similar to the PEC model but without the free nonlinear parameter. More recently, a thermodynamically consistent two-species model has been derived from non-equilibrium thermodynamics considerations and its predictions have been compared with those of the twospecies VCM model [26].…”

Section: Introductionmentioning

confidence: 99%

“…As noted above, building on the VCM model success, a thermodynamically consistent two species model has recently been derived [26]. In this new model In the present paper we carry out a comprehensive investigation of the full VCM model in shearing deformations including transient analysis from initial start up to steady state for a Taylor-Couette flow geometry.…”

Section: Introductionmentioning

confidence: 99%

Wormlike micellar solutions: III. VCM model predictions in steady and transient shearing flows

Zhou

McKinley

Cook

2014

Journal of Non-Newtonian Fluid Mechanics

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“…Further progress was recently made by Germann et al using non-equilibrium thermodynamical models, which described the shear-induced breaking of rod-shaped micelles [17,18]. These improved models could explain many rheological features which were observed in steady-state flow, small-amplitude oscillatory shear, and step strain experiments [17,18].…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical investigations of the non-linear rheological properties of viscoelastic surfactant solutions: application and failing of the one-mode Giesekus model

Rehage

Fuchs

2015

Colloid Polym Sci

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In a series of experiments, we investigated the non-linear rheological properties of aqueous solutions of entangled wormlike micelles (WLMs) in steady-state shear flow and in large amplitude oscillating shear (LAOS) experiments. On grounds of their monoexponential stress relaxation properties, we studied semi-dilute solutions of the cationic surfactants cetylpyridinium chloride (CPyCl) or cetyltrimethylammonium bromide (CTAB) after addition of different amounts of sodium salicylate. The rheological data of these networks of WLMs were systematically compared with the numerically calculated results of the one-mode Giesekus constitutive equation. It turned out that the viscous resistance and the first normal stress difference, measured in steady-state shear flow, start-up, and relaxation experiments, were accurately predicted by the one-mode Giesekus model. In rheological tests, where we applied large oscillating shear amplitudes (LAOS), the transient shear stress could also approximately be described by means of the Giesekus model. The non-linear oscillating first normal stress difference, however, showed large deviations in respect to the theoretical predictions. These discrepancies between different rheological experiments, which we observed in oscillating and stationary flow, pointed to the existence of flow instabilities, which occurred in the LAOS regime. These, more complicated rheological processes, were induced by shear-banding and/or the presence of flow-induced phase transitions, which can occur in oscillatory and stationary shear. The non-linear phenomena, discussed in this article, are of general importance, and they can be equally observed in entangled solutions of flexible macromolecules.

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Nonequilibrium thermodynamic modeling of the structure and rheology of concentrated wormlike micellar solutions

Cited by 66 publications

References 17 publications

Elongational deformation of wormlike micellar solutions

Elongational deformation of wormlike micellar solutions

Wormlike micellar solutions: III. VCM model predictions in steady and transient shearing flows

Experimental and numerical investigations of the non-linear rheological properties of viscoelastic surfactant solutions: application and failing of the one-mode Giesekus model

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