Dynamic interfacial properties and tuning aqueous foamability stabilized by cationic surfactants in terms of their structural hydrophobicity, free drainage and bubble extent

This work reports the aqueous foaming behavior of the synthesized quaternary ammonium-based conventional and Gemini surfactants (GS) varying in degree of hydrophobicity. Foamability and its stability results revealed the significance of the surfactant's hydrocarbon chain length in tuning its interfacial performance. The micellization breakpoint i.e., the critical micelle concentration (CMC), the surface activity descriptors of each surfactant were evaluated from tensiometry method at 303.15 K. Microscopic studies revealed the time dependency on the foam stability of 12-2-12 as a utility of its concentration greater than its CMC i.e., 1*CMC and 5*CMC. In addition, the dynamic rheological properties like viscosity and viscoelasticity (storage modulus, G' and loss modulus, G") of 12-2-12 were measured as a function of its concentration (1*CMC, 3*CMC, and 5*CMC) which depicted pseudo-plastic behavior. To explore the influence of shear rate, the Power-law model for foam viscosity was employed and observed to be a strong function of GS concentration. Furthermore, the oil-in-water study demonstrated the improved stabilization in the presence of GS, more evident from increasing zeta potential values of 12-2-12 than 12-2-16 and 16-2-16. The interfacial tension (IFT) study of GS for 5*CMC at the oil-aqueous interface was also commenced using several n-alkanes (n-heptane, n-decane, n-dodecane, and n-tetradecane) to make it more practicable for the industrial applications.