Spherical-to-Wormlike Micelle Transition in CTAB Solutions

Lin, Zhibin; Cai, J.; Scriven, L. E.; Davis, H. T.

doi:10.1021/j100074a027

Cited by 375 publications

(363 citation statements)

References 18 publications

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“…Surfactant concentrations are near their respective critical micelle concentrations so that micelles formed are spherical and monodisperse. 1,20,25,26,38 ODRB in its ground state is a singly charged positive ion with an 18-carbon chain that tethers it into the micelle so that the rhodamine B portion is in the headgroup region of the micelle. 60 ODRB is the molecule which is photoexcited, and its concentration is low enough that there is at most one ODRB molecule per micelle.…”

Section: Experimental Systemsmentioning

confidence: 99%

Solvent Reorganization Energy and Free Energy Change for Donor/Acceptor Electron Transfer at Micelle Surfaces: Theory and Experiment

et al. 1998

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Theories are presented for calculating the solvent reorganization energy and the free energy change which occur in photoinduced donor/acceptor electron transfer at the surface of micelles. The theories are based on the Marcus theory for spherical reactants in a dielectric continuum. The micelle is modeled with regions of differing dielectric properties, representing the micelle core, the headgroup region, and the surrounding water. The free energy change accompanying electron transfer can be calculated from redox measurements made in bulk liquids. The theories are applied to previously published photoinduced intermolecular electron-transfer data between octadecylrhodamine B (ODRB) and N,N-dimethylaniline (DMA) molecules.1 The ODRB and DMA molecules are located in the surface region of three different types of surfactant micelles: dodecyl-, tetradecyl-, and cetyl-trimethylammonium bromide (DTAB, TTAB, and CTAB, respectively). The data show an increased rate of electron transfer with increasing micelle radius. Application of the new theory to the electron-transfer data along with information provided by neutron scattering experiments show that the headgroup regions of the three micelles have different dielectric constants because water penetration into the headgroup regions decreases as the surfactant length increases.

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Section: Experimental Systemsmentioning

confidence: 99%

Solvent Reorganization Energy and Free Energy Change for Donor/Acceptor Electron Transfer at Micelle Surfaces: Theory and Experiment

et al. 1998

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“…Under certain conditions such rod-like micelles grow further and long flexible aggregates called "worm-like" or "thread-like" micelles are formed. At above a critical concentration, called the overlapping concentration (c * ), the wormlike micelles are sufficiently close to each other and because of occurring hydrodynamic interaction between the aggregates, solution viscosity becomes very high and the solution exhibits viscoelastic properties 1) that is similar to those observed in flexible polymer solutions. It is known that the worm-like micelles are formed in cationic surfactant solutions with inorganic or organic salt such as sodium bromide and sodium salicylate .…”

Section: Introductionmentioning

confidence: 99%

Composition-Insensitive Highly Viscous Wormlike Micellar Solutions Formed in Anionic and Cationic Surfactant Systems

et al. 2010

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We investigated phase behavior and rheological properties of aqueous micellar phase formed in water/cocoyl glutamate neutralized with triethanol amine (CGT-n)/hexadecyl trimethylammonium salt (CTAB or CTAC) systems, where n is a degree of neutralization. Micellar phase appears in wide composition range with respect to the surfactant mixing fraction in ternary phase diagrams at 25˚C. At high mixing fraction of cationic surfactant in the water/CGT-n/CTAB systems, one can observe a highly viscous micellar phase in which worm-like micelles are expected to form. Contrary to conventional systems in which worm-like micelles are formed, the zero-shear viscosity of the micellar solution in the water/CGTn/CTAB system with n=1.2 increases with the addition of cationic cosurfactant and once decreases after a maximum, then increases again and decreases after the second maximum. At n=1.5 and 2, highly viscous solution is observed in the relatively wide range of surfactant mixing fraction instead of two maxima of the viscosity curve observed at n=1.2. In the case of CTAC instead of CTAB we can observe narrow composition range for the maximum viscosity. Frequency sweep measurements were performed on the highly viscous samples in the water/CGT-1.5/CTAB system. Typical viscoelastic behavior of worm-like micellar solutions is observed; i.e. the curves of storage (G') and loss (G") moduli make a crossover and the data points of G' and G" can be fitted to the Maxwell model. Relaxation time against the mixing fraction of two surfactants behaves similarly to the zero-shear viscosity change, whereas the plateau modulus continuously increases in the plateau region for the zero-shear viscosity curve.

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“…For a fixed surfactant concentration C D , micelles extend from spherical to wormlike micelles with increasing co-solute concentration C S . Lin et al (1994) also showed that at low C S there is no micelle entanglement, and the solution behaved as a Newtonian fluid in Couette cell tests. Above a critical C S value, the solution had a ''Newtonian plateau" at low shear rates and then shear thickened within a higher discrete shear-rate range and at much higher shear rates the solution thinned and plateaued at the low-shear viscosity.…”

Section: Application Potentialmentioning

confidence: 89%

“…Numerous authors have investigated FIVE systems and CTAB/ NaSal specifically mostly in the context of material properties in a Couette cell (Lin et al, 1994;Vasudevan et al, 2008). For a fixed surfactant concentration C D , micelles extend from spherical to wormlike micelles with increasing co-solute concentration C S .…”

Section: Application Potentialmentioning

confidence: 99%