A systematic study of equilibrium structure, thermodynamics, and rheology of aqueous CTAB/NaNO3 wormlike micelles

Helgeson, Matthew E.; Hodgdon, Travis K.; Kaler, Eric W.; Wagner, Norman J.

doi:10.1016/j.jcis.2010.05.045

Cited by 72 publications

(74 citation statements)

References 40 publications

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“…Fig.7(b) plots L vs. 1/RT and confirms the Arrhenius dependence as predicted in Refs. [14,15]. From the slope of this plot we estimate an E c of ≈ 10k B T , consistent with experiments [13,14,20].…”

supporting

confidence: 88%

“…Figure 7(a) shows the tangent to tangent correlations n(s) · n(s + s ) = exp (−s /l p ), and the calculated l p at different T . It is remarkable that the predicted value l p ≈ 20nm, and κ ≈ 200k B TÅ are both consistent with experiments [14,28,30]. Additionally, the inset shows that l p is a constant over the temperature range of 280 − 315K.…”

supporting

confidence: 85%

“…It has long been known that the emerging superstructures can range from spherical and elongated cylindrical to very long, flexible wormlike micelles with or without branches [1][2][3][4][5][6][7][8][9] and topologically rich knotted structures [7,8]. The diversity in microstructure and rheological properties make micellar solutions beneficial to numerous applications [10] as hydrofracking fluids in oil industry, turbulent friction drag reducing agents [8], thickening agents in consumer products, drug carriers in targeted delivery [11], and templates to create functional nanofluids with tunable mechanical or optical properties [12][13][14].Since the early work of Debye [1], the microstructural transitions in micellar solutions have been investigated both theoretically [4,[15][16][17][18] and experimentally [1,2,19,20]. It is now well-recognized that the molecular structure of co-surfactant or salt has a spectacular effect on the morphology.…”

mentioning

confidence: 99%

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Topology, length scales, and energetics of surfactant micelles

Dhakal

Sureshkumar

2015

The Journal of Chemical Physics

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We investigate the morphology and energetics of a self-associating model cationic surfactant in water using coarse-grained molecular dynamics simulations. We develop an algorithm to track micelle contours and quantify various microstructural features, such as contour length, persistence length, and mesh size. We demonstrate that branched and multiconnected structures govern the anomalous dependence of zero-shear viscosity on salt concentration. We predict reliably the end-cap energy of micelles, for the first time, directly from the simulations.In aqueous solutions, surfactant molecules spontaneously self-assemble into diverse geometrically complex and dynamically fluctuating morphologies. It has long been known that the emerging superstructures can range from spherical and elongated cylindrical to very long, flexible wormlike micelles with or without branches [1][2][3][4][5][6][7][8][9] and topologically rich knotted structures [7,8]. The diversity in microstructure and rheological properties make micellar solutions beneficial to numerous applications [10] as hydrofracking fluids in oil industry, turbulent friction drag reducing agents [8], thickening agents in consumer products, drug carriers in targeted delivery [11], and templates to create functional nanofluids with tunable mechanical or optical properties [12][13][14].Since the early work of Debye [1], the microstructural transitions in micellar solutions have been investigated both theoretically [4,[15][16][17][18] and experimentally [1,2,19,20]. It is now well-recognized that the molecular structure of co-surfactant or salt has a spectacular effect on the morphology. In particular, aromatic organic salts have stronger binding affinity to the micelles and induce enormous growth. Consequently, micelles become very long, flexible and entangle even at relatively low surfactant concentration c D . Dilute solutions with spherical or short cylindrical structures exhibit Newtonian fluid rheology [19][20][21]. In contrast, solutions above the overlap concentration φ * consist of very long-thread like structures with contour lengths that span from a few 10s of nm to several µm, and show viscoelastic behavior reminiscent of flexible polymer solutions [4,19,20]. However, unlike polymers, WLMs can merge and undergo reversible breaking at time scales that are detectable both in scattering experiments and simulations. Under non-equilibrium conditions, such as, under shear flow, the structure, dynamics, and the resultant rheological properties could change dramatically: two notable examples are the shear induced structure (SIS) formation, and shear banding [19][20][21][22][23][24][25][26][27]. Due to such dynamical complexities, a quantitative description of the microstructure of micellar fluids is incomplete. In this paper, we present a comprehensive simulation study of self-assembly, emerging structures, length scales, and the energetics of a model surfactant solution with explicit solvent, electrostatic and hydrodynamic interactions.Despite decades of research aimed ...

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supporting

confidence: 88%

supporting

confidence: 85%

mentioning

confidence: 99%

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Topology, length scales, and energetics of surfactant micelles

Dhakal

Sureshkumar

2015

The Journal of Chemical Physics

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“…7(b)], the scaling exponent t fil / g a 0 decreases from a ¼ 1:3 to a ¼ 0:9 at a critical salt/surfactant value R ¼ 5.7 indicating a linear to branched micelles transition. This hypothesis is further supported by cryo-TEM images [Helgeson et al (2010)] and by Oelschlaeger et al [Oelschlaeger et al (2010)] who observed a characteristic increase of the plateau modulus G 0 at R % 5:0 for a 350 mM CTAB/NaNO 3 solution.…”

Section: E Low Salt Regimementioning

confidence: 59%

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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“…The zeta potential of HA changes from positive to negative when the GN is adsorbed, and it reaches the maximum absolute value for 0.5 wt% addition. The maximum of zeta potential implies that the HA surface is completely covered with GN at this pH (7-8) [51]. Fig.…”

Section: Ha/gn Layer Prepared By Epdmentioning

confidence: 84%