Synthesis of a New Zwitterionic Surfactant Containing an Imidazolium Ring. Evaluating the Chameleon-like Behavior of Zwitterionic Micelles

Synthesis of a new zwitterionic surfactant containing the imidazolium ring 3-(1-tetradecyl-3-imidazolio)propane-sulfonate (ImS3-14) is described. The solubility of ImS3-14 is very low but increases on addition of a salt which helps to stabilize the micellized surfactant. Fluorescence quenching and electrophoretic evidence for ImS3-14 shows that the micellar aggregation number is only slightly sensitive to added salts, as is the critical micelle concentration, but NaClO4 markedly increases zeta potentials of ImS3-14 in a similar way as in N-tetradecyl-N,N-dimethylammonio-1-propane-sulfonate (SB3-14) micelles. The rate of specific hydrogen ion catalyzed hydrolysis of 2-(p-heptoxyphenyl)-1,3-dioxolane and equilibrium protonation of 1-hydroxy-2-naphthoate ion in zwitterionic micelles of ImS3-14 and SB3-14 are increased markedly by NaClO4 which induces anionoid character and uptake of H3O+, but NaCl is much less effective in this respect. Comparison of ImS3-14 with SB3-14 is based on experimental evidence, and computational calculations indicate similarities and differences in structures of both compounds.