Effect of electrolytes on the interfacial rheological behaviors of N-cocoyl glycinate

Amino acid surfactants have been applied to numerous areas of science and are often used in the presence of electrolytes. In this study, the interfacial rheological behaviors of potassium N-cocoyl glycinate (KCGl), an amino acid surfactant, with three kinds of electrolytes (KCl, CaCl2 and tetrabutylammonium bromide (TBABr)) have been investigated using the oscillating drop method. The interfacial tensions (IFTs) and dilational rheological parameters show that KCGl in conjunction with electrolytes has enhanced interfacial activity and stronger intermolecular interaction than pure KCGl, indicating that electrolytes contribute to denser molecular packing at the oil-aqueous interface. Interestingly, the butyl groups of TBA(+) hinder closer arrangement of molecules at the interface, hindering KCGl ability to form a tightly packed layer compared with K+ and Ca2+ electrolytes. The relaxation processes, such as diffusion exchange of surfactant molecules between the aqueous phase and interface, are more probable to occur. Therefore, more viscoelastic films are formed in the presence of TBABr. [GRAPHICS] .