1-butanol and 3,3-dimethyl-1-butanol as cosurfactants of the laurylsulfobetaine/water system

Phase and theological behaviors for laurylsulfobetaine with 1-butanol and with 3,3-dimethyl-1-butanol at 30.0 +/- 0.1 degreesC are presented. Both systems show three liquid crystal phases: lamellar, hexagonal and cubic. Only one micellar phase appears with l-butanol while two different micellar phases (L-1 and L-2) appear with the branched alcohol. For the system with 1-butanol, the transition from normal to reverse micelles goes through bicontinuous structures without phase separation. The shape of the mixed laurylsulfobetaine/1-butanol micelles in water change from spherical to large cylindrical micelles with the surfactant content. For the system with 3,3-dimethyl-1-butanol, the normal micelles in water solution are small and spherical and they exist in a narrow range of alcohol content. The reverse micelles in l-butanol are larger than in 3,3-dimethyl-1-butanol. The extension of the cubic phase is the same for both systems. This phase is the most viscous phase with elastic properties which fits to the Maxwell model at low frequencies. On the contrary, the extension of lamellar and hexagonal phases is different depending of the alcohol structure. The formation of lamellar phase is favoring for the branched alcohol while the hexagonal region is larger for the system with the linear alcohol. Both phases show also viscoelastic properties but they do no fit to Maxwell model. (C) 2001 Elsevier Science B.V. All rights reserved.