Reversible formation/disruption of dynamic double-tailed surfactants in a binary mixture: effects on interfacial properties and aggregation behavior

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 636; p. 128141
• Main Authors: Zhang, Yongmin, Mu, Meng, Lu, Pingping, Zhao, Shanjuan, Fan, Ye, Liu, Xuefeng, Fang, Yinjun
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.03.2022
• Subjects: Double-tailed surfactant; Dynamic covalent; Imine bond; Micelles; Symmetry; Vesicles; Vesicles; Double-tailed surfactant; Micelles; Dynamic covalent; Imine bond; Symmetry
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2021.128141

Dynamic covalent chemistry provides numerous possibilities to develop various amphiphiles. However, the design of responsive amphiphiles bearing tunable symmetry based on dynamic covalent bonds is still a challenge. Herein, a dynamic double-tailed surfactant (DDTS) was produced in situ by mixing aldehyde-type amphiphile (N-hexadecyl-N,N-dimethyl-N-(2-(4-formyl-phenoxy)ethyl) ammonium bromide, HOBAB) and commercial octylamine (OA) with a stoichiometric ratio of 1:1. After equilibrium (pH = 10.0), the composition were 68% DDTS, 16% HOBAB and 16% OA. The predominant surfactant in the solution can be reversibly tuned between highly asymmetrical HOBAB and approximately symmetrical DDTS by alternately adding acid (pH = 5.0) and base (pH = 10.0) due to the pH sensitivity of imine bonds. The presence of DDTS significantly decreased the critical micelle concentration, enhanced the adsorption efficiency at the interface and the effectiveness in surface tension reduction, and thermodynamically facilitated the formation of aggregates. More importantly, the emergence of DDTS triggered a transformation from spherical micelles to vesicles, because of the increase in symmetry of the amphiphiles. Once DDTS was disrupted upon decreasing the pH, the opposite transformation ensued. Such a transformation between micelles and vesicles could also be triggered by altering the choice of alkylamine. The present work provides an alternative way to control the transformation between micelles and vesicles, which is favorable for the design of new responsive soft colloids and exploration of their potential applications. [Display omitted] •Dynamic double-tailed surfactant with tunable symmetry was developed by Schiff base reaction.•The symmetry can be tuned by changing pH or alkylamines.•The formation and extension of hybrid tail facilitated to enhance interfacial properties.•Approximately symmetrical double-tailed structure was thermodynamically favorable for micellization and stable interface.•The symmetry significantly impacted the aggregation behavior.