Synthesis, Micellization, and Surface Activity of Novel Linear‐Dendritic Carboxylate Surfactants

Abstract Two generations of novel linear‐dendritic carboxylate surfactants C 18 ‐G 1 ‐(COONa) 2 and C 18 ‐G 2 ‐(COONa) 4 have been synthesized by the divergent method and their structures are characterized by 1 H Nuclear Magnetic Resonance and Infrared analysis. The electrical conductivity measurement is used to measure the Krafft temperatures of C 18 ‐G 1 ‐(COONa) 2 and C 18 ‐G 2 ‐(COONa) 4 , which are much smaller than those of the corresponding conventional surfactant sodium stearate. The markedly enhanced solubility of two linear‐dendritic surfactants is ascribed to the high hydrophilicity of surfactant headgroups induced by the carboxylate and ester groups. The critical micelle concentration (CMC) values obtained from both the electrical conductivity and surface tension measurements indicate that the micellizations of linear‐dendritic surfactants become favorable with the increase in the number of the surfactant headgroup. However, the surface activity parameters including the surface tension at the CMC, maximum surface excess, and minimum surface area reveal that C 18 ‐G 1 ‐(COONa) 2 exhibits greater efficiency in absorbing at the air/water interface compared to C 18 ‐G 2 ‐(COONa) 4 , owing to their different steric repulsions of the surfactant headgroups. In addition, C 18 ‐G 1 ‐(COONa) 2 and C 18 ‐G 2 ‐(COONa) 4 have higher emulsifying ability than the conventional surfactants sodium stearate and sodium octadecyl sulfate.