Abstract:

The worm-like micelles formed by the mixture of an anionic surfactant （sodium α-olefin sulfonate, AOS） and a zwitterionic surfactant （lauramidopropyl hydroxysulfobetaine, LHSB） as induced by Mn²⁺ ions were studied. The influencing factors studied included the mass ratio between the two surfactants, the mass fraction of Mn²⁺, the mass fraction of surfactants, and the temperature. The results showed that, the viscosity of the surfactant solution first increased and then decreased as the mass ratio of AOS:LHSB was increased and the mass fraction of Mn²⁺ was increased. The zero-shear viscosity of the system exhibited an exponential increase with increasing mass fraction of surfactants. The viscosity measurement was conducted at 25 ℃. The maximum viscosity was obtained when the mass ratio of AOS:LHSB was 3:7, and the optimal Mn²⁺ content was 0.5% when the mass fraction of surfactants was 2% （the zero-shear viscosity at this optimal condition was measured to be 9 030.9 mPa·s）. The morphology of the micelles in solution was observed using Cryo-TEM, revealing long worm-like micelles with a tight network structure and good linear viscoelasticity. The mass fraction of surfactants and the presence of Mn²⁺were found to have significant influence on the formation of worm-like micelles. This study could provide important additional information for the preparation of worm-like micelles using mixed anionic-zwitterionic surfactant system.

Key words: anionic surfactant, zwitterionic surfactant, worm-like micelle, metal ion regulation