Synthesis and Interfacial Properties of Imidazoline Surfactants

Quaternary ammonium salts of 2‐undecyl (heptadecyl)‐1‐dithioureido‐ethyl‐imidazoline (SUDEI/SHDEI) have been synthesized, and their interfacial properties are investigated. The effects of temperature, alkyl chain R length, and polarity of solvents on the surface tension are discussed. The results show that surface tension of SUDEI and SHDEI in water solutions decreases with increasing of temperature, and SHDEI shows lower cmc value than SUDEI at constant temperature, indicating that it is easier for SHDEI to form micelles in water. SUDEI and SHDEI show much higher cmc in ethanol‐water (1∶4, v/v) than that in pure water. The molecular structure of SUDEI/SHDEI is composed of lipophilic group R and hydrophilic group comprising active elements S, N and imidazoline ring and the two groups are of similar length, which is similar to that of bi‐block copolymer. Thus, interesting results have been found in the preparation of nanomaterials in the presence of imidazoline surfactants. The corresponding mechanisms are still under investigation.

Keywords:

• Imidazoline surfactants
• synthesis
• interfacial properties
• nanomaterials

The authors wish to acknowledge the financial support from the foundation of Ph.D. subjects 2005 (Grant No. 20050426003) and the State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Science (Grant No. 0402).