Solutions viscoelastic micellar

Perhaps the most important distinction between classical solids and classical liquids is that the latter quickly shape themselves to the container in which they reside, while the former maintain their shape indefinitely. Many complex fluids are intermediate between solid and liquid in that while they maintain their shape for a time, they eventually flowr They are solids at short times and liquids at long times hence, they are viscoelastic. The characteristic time required for them to change from solid to liquid varies from fractions of a second to days, or even years, depending on the fluid. Examples of complex fluids with long structural or molecular relaxation times include glass-forming liquids, polymer melts and solutions, and micellar solutions. 

As remarked earlier, the nonlinear viscoelastic behavior of entangled wormy micellar solutions is similar to that of entangled flexible polymer molecules. Cates and coworkers (Cates 1990 Spenley et al. 1993, 1996) derived a full constitutive equation for entangled wormy micellar solutions, based on suitably modified reptation ideas. The stress tensor obtained from this theory is (Spenley et al. 1993)... 

Many surfactant solutions are normal Newtonian liquids even up to rather high concentrations. Their viscosities are very small as compared with the viscosity of the solvent water. This is particulary the case for micellar solutions with concentrations up to 20% W/W in which spherical micelles are present. Even in the presence of rodlike micelles the viscosities can be rather low. Systems with rodlike micelles have recently been studied extensively. Missel et al. (1-2) studied alkylsulfate solutions and showed how the lengths of the rods can be varied by the addition of salt or by the detergent concentration. Under all these conditions the solutions are of rather low viscosity. On the other hand, we have studied a number of cationic detergent solutions in which rodlike micelles were formed and which all became quite viscous at rather low concentrations. In addition some of these solutions had elastic properties. The phenomenon of viscoelasticity in detergent solutions is not new. Exten-... 

Kunieda s group reported numerous viscoelastic worm-like micellar systems in the salt-free condition when a lipophilic nonionic surfactant such as short hydrophilic chain poly(oxyethylene) alkyl ether, C EOni, or N-hydroxyethyl-N-methylaUcanolamide, NMEA-n, was added to the dilute micellar solution of hydrophilic cationic (dodecyltrimethylammonium bromide, DTAB and hexade-cyltrimethylammonium bromide, CTAB) [12-14], anionic (sodium dodecyl sulfate, SDS [15, 16], sodium dodecyl trioxyethylene sulfate, SDES [17], and Gemini-type [18]) or nonionic (sucrose alkanoates, C SE [9, 19], polyoxyethylene cholesteryl ethers, ChEO [10, 20], polyoxyethylene phytosterol, PhyEO [11, 21] and polyoxyethylene sorbitan monooleate, Tween-80 [22]) surfactants. The mechanism of formation of these worm-Hke stmctures and the resulting rheological behavior of micellar solutions is discussed in this section based in some actual published and unpublished results, but conclusions can qualitatively be extended to aU the systems studied by Kunieda s group. 

As already stated, several studies have been pubUshed using nonionic surfactant systems. The formation of viscoelastic micellar solutions in mixed nonionic systems is interesting in basic research-as the relation between packing constraints of hydrophobic chains and micellar growth would be clarified since the complicated interaction between the counterion and headgroup does not occur-as well as in applications such as cosmetics or pharmacy, where the avoidance of ionic additives is often desirable. 

Acharya, D.P., and Kunieda, H. (2003) Formation of viscoelastic wormlike micellar solutions in mixed nonionic surfactant systems. J. Phys. Chem. B, 107, 10168-10175. 

Effect of C12EOn mixed-surfactant systems on the formation of viscoelastic wormlike micellar solutions in sucrose alkanoate- and CTAB-water systems. Colloid Surf A, 279,113-120. 

Clausen TM, Vinson PK, Minter JR et al (1992) Viscoelastic micellar solutions microscopy and rheology. J Phys Chem 96 474 84... 

Oda R, Narayanan J, Hassan P, Manohar C, Salkar R, Kern F, Candau S (1998) Effect of the lipophUicity of the counterion on the viscoelasticity of micellar solutions of cationic surfactant. Langmuir 14 4364 372... 

Cappelaere E, Cressely R (1997) Shear banding stmeture in viscoelastic micellar solutions. CoUoid Polym Sd 275(5) 407- 18... 

Raghavan SR, Kaler EW (2001) Highly viscoelastic wormlike micellar solutions formed by cationic surfactants with long unsaturated tails. Langmuir 17(2) 300-306... 

Qausen T, 56nson P, Minter J, Davis H, Talmon Y and Miller W. 1993 Viscoelastic micellar solutions -microscopy and theology. Journal of Physical Chemistry 474-484. 

Imai, S.-i., Shikata, T. Viscoelastic behavior of surfactant threadlike micellar solutions effect of additives 3. J. Colloid Interface Sci. 2001, 244(2), 399-404. Olsson, U., Soderman, O., Guering, P. Characterization of micellar aggregates in viscoelastic surfactant solutions a nuclear magnetic resonance and hght scattering study. J. Phys. Chem. 1986, 90(21), 5223-5232. 

A Simple Model to Predict Nonlinear Viscoelasticity and Shear Banding Flow of Wormlike Micellar Solutions... 

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