Synthesis and Surface Active Properties of a Gemini Imidazoline Amphoteric Surfactant

The gemini imidazoline amphoteric surfactant was prepared in two steps. We first reacted lauric acid and triethylenetetramine to obtain the intermediate called bisalkyl-bis-imidazoline. We analyzed it by H-1 NMR, and the yield was 82.45 % according to perchloric acid non-aqueous titration. The intermediate was then quaternized using sodium 2-chloroethanesulfonic acid in a mixture of isopropyl alcohol and water, during which we controlled the pH between 8 and 9 and the temperature between 80 and 90 A degrees C to prepare C12-bis-imi. The air-liquid surface tension was measured by a tensiometer at 298 +/- 0.1 K. The results show that the critical micelle concentration (CMC) was 2.25 x 10(-3) mol/L and the surface tension at the CMC (gamma (CMC)) was 30.42 mN/m. C12-bis-imi showed a synergistic effect in combination with lauric alcohol with nine ethylene oxide groups (AEO9). The synergistic effect is most striking when the mole ratio of C12-bis-imi/AEO9 was 1/1, and the corresponding CMC was 9.79 x 10(-5) mol/L and the gamma (CMC) was 37.61 mN/m.