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 w ith 3,3-dimethyl-1-butanol at 30.0 +/- 0.1 degreesC are presented. Both sys tems show three liquid crystal phases: lamellar, hexagonal and cubic. Only one micellar phase appears with l-butanol while two different micellar phas es (L-1 and L-2) appear with the branched alcohol. For the system with 1-bu tanol, the transition from normal to reverse micelles goes through bicontin uous structures without phase separation. The shape of the mixed laurylsulf obetaine/1-butanol micelles in water change from spherical to large cylindr ical micelles with the surfactant content. For the system with 3,3-dimethyl -1-butanol, the normal micelles in water solution are small and spherical a nd 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 ph ase with elastic properties which fits to the Maxwell model at low frequenc ies. On the contrary, the extension of lamellar and hexagonal phases is dif ferent depending of the alcohol structure. The formation of lamellar phase is favoring for the branched alcohol while the hexagonal region is larger f or the system with the linear alcohol. Both phases show also viscoelastic p roperties but they do no fit to Maxwell model. (C) 2001 Elsevier Science B. V. All rights reserved.