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

Abstract

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.

Effects of Spacer Chain Length of Amino Acid-Based Gemini Surfactants on Wormlike Micelle Formation

“…Hence, the resulting rheological data suggest that anionic wormlike micelles were formed at low HTAB concentrations including the composition where the maximum η 0 value was obtained , and were subsequently transformed into cationic wormlike micelles at relatively high HTAB concentrations. This behavior is very similar to that observed for the cocoyl glutamate that was partially neutralized by the triethanol amine/ HTAB/water system 13 .…”

Wormlike Micelle Formation by Acylglutamic Acid with Alkylamines

“…The other chemicals including NaBr, HCl, NaOH, ethanol, acetone, and ethyl acetate were of analytical grade and used without further purification. CDCl 3 including tetramethylsilane as an interior reference (Wako), D 2 O (Wako), NaOD (Cambridge Isotope Laboratories, Inc.), and sodium (3-trimethylsilyl)-1-propanesulfonate (Aldrich) were used for 1 H-and 13 C NMR measurements. The water used in this study was deionized with a Barnstead NANO Pure Diamond UV system and filtered with a Millipore membrane filter (0.22 μm pore size).…”

Coacervation in Cationic Polyelectrolyte Solutions with Anionic Amino Acid Surfactants

“…1. The carbon number n in the cocoyl group varied in the range 7-17, and the average n was 11.3 22 . Deionized water, obtained from an Elix 3 Nihon Millipore water purification system, was used as the solvent.…”