Synthesis of anionic carboxylate dimeric surfactants and their interactions with electrolytes

The present work was a systematic study of the carboxylate anionic dimerics (CAD) N-methyldodecylamine and ethylene diaminetetraacetic acid dianhydride to investigate their synthesis, characterization, surface and salt behaviour. CAD were synthesized with two solvents at various temperatures. Fourier transform infrared spectroscopy was used to identify the functional groups of CAD, and 1H and 13C nuclear magnetic resonance were used to determine the type of proton and for carbon atom confirmation in the synthesized moiety, respectively. The effects of inorganic (NaCl, KCl) and organic salts (sodium salicylate and sodium benzoate) on surface activity were estimated by tensiometric methods. All the salts lowered the critical micelle concentration of the synthesized dimeric surfactant, the organic salts to a greater extent than the inorganic salts, in the sequence sodium salicylate > sodium benzoate > KCl > NaCl.