Design and Surface/Interfacial Properties of Asymmetric Triazine Carboxyl Betaine Surfactants

The design, synthesis and interfacial behaviors of six asymmetric carboxyl betaine surfactants (BC_m?n, m, n = 8, 10, 12, or 14, m ≠ n) derived from s‐triazine, which were prepared from cyanuric chloride, aliphatic amines, N,N‐dimethylpropane‐1,3‐diamine, followed by the reaction with sodium chloroacetate, are reported. The structures were confirmed by MS, ¹H NMR and FT‐IR. Compared with symmetric surfactants (BC_n?n, n = 8, 10, 12, or 14) we previously synthesized, the asymmetric series show superior surface activity. The γ_CMC of surfactants BC_10?8, BC_12?8, BC_14?8 and BC_12?10 is all below 30 mN/m. The minimum alkane carbon number of these ten surfactants is determined to be between 10 and 14. The interfacial behaviors between the alkanes and the solutions of triazine carboxyl betaine surfactants show that surfactants with a total carbon number in hydrophobic chains between 16 and 22 exhibit the ability to reduce the interfacial tension to an ultra‐low value (10^?3 mN/m). The surfactants with longer hydrocarbon chains display strong affinity to the alkanes with longer chains.