Cryogenic wormlike micellar solutions with a freezing point far below 0 °C and unique rheological behavior are fabricated from the self-assembly of a C22-tailed zwitterionic surfactant in a mixed solvent of ethylene glycol and water. Such fluids could find applications in areas where viscoelasticity is highly desired at subfreezing temperatures.

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Rheological measurements were performed to understand the effect of benzyltrimethyl ammonium bromide (BTAB) and NaBr on the growth of wormlike micelles formed by sodium oleate (NaOA). Both salts can make the micellar solution viscoelastic, and the rheological responses verify the formation of wormlike micelles. The viscoelastic solution follows the Maxwell model of a single stress relaxation mode in the low‐frequency region. In comparison, the BTAB system exhibits stronger viscoelasticity than the NaBr system at constant salt concentration, but the critical overlapping concentration shows no significant difference; less BTAB can induce the solution to be more viscous than NaBr, but the viscosity maximum of the BTAB system is remarkably lower than that of NaBr at fixed NaOA content. The puzzling result is attributed to the effect of the composition on the packing parameter. In addition, it is shown that the zero‐shear viscosity of the two salt systems decreases upon heating, following the Arrhenius mode well.

The electrostatic effects on the synergism between wormlike micelles and hydrophobically modified polyacrylic acid (HMPA) have been investigated by rheological measurements and dissipative particle dynamics molecular simulation (DPD). Both cationic surfactants, cetyltrimethylammonium bromide (CTAB), and anionic surfactant, sodium oleate (NaOA), were employed to construct wormlike micelles, and the influences of both simple salts, NaBr or NaAc, and hydrophobic salts, sodium benzoate (NaBen) and benzyltrimethyl ammonium bromide (BTAB), were discussed. The synergistic effects vary with the headgroup charge and the counterions property of surfactants. For the NaOA system, the obvious viscosity maximum was observed only at low NaAc content, while a monotonous viscosity increase appeared at a high content of BTAB. However, the optimal synergism can be only observed in the presence of concentrated NaBen in CTAB system. DPD molecular simulation provides a support and favorable illustration for the synergism mechanism. It suggests that not only the hydrophobic interaction but also the electrostatic interaction has an important impact on the synergism between ionic wormlike micelles and HMPA.