The partial phase behavior of CTAT/water is investigated here as a function of temperature by WAXS, DSC, polarizing microscopy, conductometry, 1H-NMR, and FTIR spectroscopy. Oscillatory strain and temperature sweeps are also reported. The Krafft temperature (7k) of CTAT/water is 23 °C. Below this value, triclinic crystals of CTAT coexist with an isotropic solution. Above 7k and at low concentrations, spherical micellar solutions are Newtonian and exhibit low viscosities. At higher concentrations (ct), cylindrical micelles form and viscosity increases dramatically with CTAT concentration, but no elastic effects are noticed. When micelles are long enough to entangle (0.9-27 wt % at 25 °C), clear viscoelastic solutions form. At higher concentrations and up to 47 wt %, an hexagonal phase appears. This phase exhibits yield stress and viscoelasticity. At higher concentrations, a nonelastic, viscous solid paste forms. Micellar solutions and hexagonal phase depicts three regimes of viscoelasticity with temperature. These regimes are bounded by T\ and by the temperature (TV) at which the system exhibits its main relaxation time. 77 moves to lower temperatures as CTAT concentration increases indicating that the main relaxation time decreases upon increasing concentration.

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Ascorbyl palmitate (ASC(16)) is a molecule of potential pharmacological interest due to its antioxidant properties and amphiphilic nature. The surface behavior of ASC(16) was studied using Langmuir monolayers and Brewster angle microscopy. This molecule formed stable monolayers at room temperature that showed phase transition from a liquid-expanded to liquid-condensed or crystalline phase, depending on the subphase conditions. Using a theoretical approach, we were able to explain the behavior of the ASC(16) film at different bulk pH values and salt conditions based on the surface pH and the dissociation fraction of the film. Both condensed phases corresponded to highly packed conditions with the crystalline phase occurring at a low charge density, showing molecular tilting and preferential growth at characteristic angles, while the liquid-condensed phase formed in highly charged surfaces revealed small flowerlike domains probably as a consequence of internal dipole repulsion. A smaller perpendicular dipole moment was observed for the crystalline than the liquid-condensed phase which may explain the domain features. In conclusion, ASC(16) showed a complex surface behavior that was highly sensitive to subphase conditions.