Synthesis and Surface Properties of Novel Carboxylic Ester-Containing Imidazolium-Based Zwitterionic Surfactants: Monoalkyl 2-(3-Methylimidazolium-1-yl) Succinate Inner Salts

A series of carboxylic ester-containing imidazolium-based zwitterionic surfactants, namely, monoalkyl 2-(3-methylimidazolium-1-yl) succinate inner salts (C n MimSU, n = 8, 10, 12 and 14), have been synthesized. Their structures were confirmed by 1 H NMR, 13 C NMR and FTIR. The typical physicochemical properties parameters such as isoelectric point, critical micelle concentration (CMC), surface tension at CMC ( γ CMC ), surface pressure at CMC (Π CMC ), adsorption efficiency (p C 20 ), the maximum surface excess ( Γ m ), the minimum molecular cross-sectional area ( A min ) and the value of CMC/ C 20 were determined. The effect of the long-chain length on the important physicochemical properties of C n MimSU was studied. It is found that the surface activity of C n MimSU is enhanced with the long-chain length increases.