Synthesis, Characterization and Surface Properties of Amidosulfobetaine Surfactants Bearing Odd-Number Hydrophobic Tail

Abstract

Three amidosulfobetaine surfactants were synthesized namely: 3‐(N‐pentadecanamidopropyl‐N,N‐dimethyl ammonium) propanesulfonate (2a); 3‐(N‐heptadecanamidopropyl‐N,N‐dimethyl ammonium) propanesulfonate (2b), and 3‐(N‐nonadecanamidopropyl‐N,N‐dimethyl ammonium) propanesulfonate (2c). These surfactants were prepared by direct amidation of commercially available fatty acids with 3‐(dimethylamino)‐1‐propylamine and subsequent reaction with 1,3‐propanesultone to obtain quaternary ammonium salts. The synthesized surfactants were characterized by IR, NMR and mass spectrometry. Thermogravimetric analysis (TGA) results showed that the synthesized surfactants have excellent thermal stability with no major thermal degradation below 300 °C. The critical micelle concentration (CMC) values of the surfactants 2a and 2b were found to be 2.2 × 10−4 and 1.04 × 10−4 mol/L, and the corresponding surface tension (γCMC) values were 33.14 and 34.89 mN m−1, respectively. The surfactants exhibit excellent surface properties, which are comparable with conventional surfactants. The intrinsic viscosity of surfactant (2b) was studied at various temperatures and concentrations of multi‐component brine solution. The plot of natural logarithm of relative viscosity versus surfactant concentration obtained from Higiro et al. model best fit the surfactant behavior. Due to good salt resistance, excellent surface properties and thermal stability, the synthesized surfactant has potential to be used in various oil field applications such as enhanced oil recovery, fracturing, acid diversion, and well stimulation.