Interaction between Zwitterionic Surface Activity Ionic Liquid and Anionic Surfactant: Na+-Driven Wormlike Micelles

The physicochemical properties of the mixed zwitterionic surface activity ionic liquid/anionic surfactant (N-alkyl-N'-carboxymethyl imidazolium inner salts/sodium dodecyl sulfate, [N-C-12, N'-CO2-Im]/SDS) at various molar ratios (R-I = C-[N-C12,C-N'-CO2-Im]/(C-[N-C12,C-N'-CO2-Im] + C-SDS) were investigated by surface tension and steady-state fluorescence measurements. The results show that the mixed [N-C-12, N'-CO2-Im]/SDS system has a much lower cmc value and higher surface activity than individual surfactant. Compared with the mixed zwitterionic betaine surfactant/SDS system, the mixture studied exhibits a stronger synergism, i.e., more negative interaction parameters (beta(m) and beta(sigma)). Through addition of NaCl, the wormlike micelles (WMs) could be formed in a [N-C-12, N'-CO2-Im]/SDS system. Steady and dynamic rheology was employed to characterize the WMs with different surfactant ratio (R1), NaCl concentration, and temperature. An optimal composition, viz., C-T = 60 mM, R, = 0.45, and C-NaCl = 0.10 M, was detected to form the strongest and longest wormlike micelles. Compared with the WIsAs formed by a traditional zwitterionic C-12 betaine/anionic surfactant mixture (e.g., laurylamidopropyl betaine/SDS), the WMs studied have a stronger network structure, which is expected to have potential applications in some fields, such as in nanomaterials synthesis, personal care products, and flooding liquid for tertiary oil recovery.