Interfacial Dilational Rheology of Sodium Lauryl Glycine and Mixtures with Conventional Surfactants.

Amino acid‐based surfactants are environmentally friendly surfactants, which have aroused increasing interest. In the application of amino acid‐based surfactants, they are often compounded with other kinds of surfactants to obtain formulations that meet certain requirements. Herein, sodium lauroyl glycinate (C12‐Gly‐Na) was selected as a representative amino acid‐based surfactant to compound with an anionic surfactant (sodium dodecyl sulfate [SDS]), a cationic surfactant (dodecyl trimethyl ammonium Bromide), and a nonionic surfactant (Triton X‐100: p‐octyl polyethylene glycol phenyl ether). Surface tension measurements and interfacial dilational rheological experiments were performed to study the interfacial behaviors of C12‐Gly‐Na and its mixtures. The results show that mixture systems have better interfacial activity than individual C12‐Gly‐Na and there is an obvious synergy between C12‐Gly‐Na and C12TAB under strong electrostatic attraction. Thus, the C12‐Gly‐Na/C12TAB mixture shows lower critical micelle concentration (CMC) and γCMC and higher dilational modulus than the individual surfactants. Besides, the film formed by the C12‐Gly‐Na/C12TAB mixture has higher viscoelasticity than single C12‐Gly‐Na and its mixtures with SDS and TX‐100. With the increase of bulk concentration, the dilational moduli of C12‐Gly‐Na, C12‐Gly‐Na/SDS, and C12‐Gly‐Na/TX‐100 run through two maxima, while, due to stronger electrostatic attraction, only one maximum appears in the C12‐Gly‐Na/C12TAB system. The study of the interfacial properties of amino acid surfactant and its mixtures with other surfactants provides a theoretical foundation for potential applications in cosmetic, food processing, and daily chemical industries. [ABSTRACT FROM AUTHOR]