Effect of C 12EO n mixed surfactant systems on the formation of viscoelastic worm-like micellar solutions in sucrose alkanoate– and CTAB–water systems

Abstract

With successive addition of mixed polyoxyethylene dodecylether (C 12EO n ) surfactant with an average EO number of 3 to the aqueous solution of hexadecyltrimethylammonium bromide (CTAB) and sucrose monohexadecanoate (P1695), one-dimensional micellar growth occurs and the viscosity increases sharply leading to the formation of viscoelastic solutions of worm-like micelles. Steady and oscillatory shear rheological measurements show that in the aqueous CTAB system, the extent of micellar growth decreases with increasing the dispersion in EO chain in the mixture in following order C 12EO 3 > C 12EO 2 + C 12EO 4 > C 12EO 0 + C 12EO 4 > C 12EO 1 + C 12EO 5. With C 12EO 0 + C 12EO 6 no micellar growth occurs but a phase separation is observed. In P1695 system, the viscoelastic solution is formed at relatively lower concentration of mixed C 12EO n and the extent of micellar growth decreases in the following order: C 12EO 3 ≈ C 12EO 2 + C 12EO 4 > C 12EO 1 + C 12EO 5 > C 12EO 0 + C 12EO 6. The effect of the dispersion of EO chain length on the micellar growth is also discussed.