Aqueous gels of mixtures of ionic surfactant SDS with pluronic copolymers P123 or F127

Gel diagrams based on tube inversion and oscillatory rheometry are reported for Pluronic copolymers F127 (E(98)P(67)E(98)) and P123 (E(21)P(67)E(21)) in mixtures with anionic surfactant sodium dodecyl sulfate (SDS). Total concentrations (c, SDS+copolymer) were as high as 50 wt % with mole ratios SDS/copolymer (mr) in the ranges 1-5 (F127) and 1-7 (P123). Temperatures were as high as 90 degrees C. Determination of the temperature dependences of the dynamic moduli served to confirm the gel boundaries from tube inversion and to reveal the high elastic moduli of the gels, e.g., compared at comparable positions in the gel phase, a 50 wt % SDS/P123 with mr = 7 had G' three times that of a corresponding gel of P123 alone. Small-angle X-ray scattering (SAXS) was used to show that the structures of all the SDS/F127 gels were bcc and that the structures of the SDS/P123 gels with mr = 1 were either fcc (c = 30 wt %) or hex (c = 40 wt %). Assignment of structures to SDS/P123 gels with values of mr in the range 3-7 was more difficult, as high-order scattering peaks could be very weak, and at the higher values of c and mr, the SAXS peaks included multiple reflections.