Wormlike micelles constructed by a highly water-soluble carboxylate surfactant containing a phenoxy and nonionic surfactant

Limited wormlike micelles were formed from anionic surfactants, especially for carboxylate surfactants due to their poor solubility. As we all know sodium hexadecanoate (C16Na) has a higher Krafft point (60 °C). Introducing a phenoxy at α-position of C16Na, a new carboxylate surfactant, sodium 2-phenoxyhexadecanoate (C16phNa), was synthesized. And the aqueous solution of C16phNa could keep water-like even at a concentration of 2 M at 25 °C. Wormlike micelles were successfully constructed by adding tri(oxyethylene) monododecyl ether (C12EO3) into the dilute solution of C16phNa. Steady state and dynamic rheological measurements were used to investigate the viscoelasticity of C16phNa/C12EO3 wormlike micellar solution. The results show zero shear viscosity (η0) and relaxation time (τRmax) increase at first and then decrease with the increasing concentration of C16phNa or ratio of C12EO3 and C16phNa. The value of η0 in the system could reach 2194.4 Pa·s. In addition, η0 is extremely dependent upon the concentration of C16phNa. And the value of exponents between the η0 and concentration is 13.1, 20.2 and 18.3 for a 1:1, 1:1.5 and 1:1.8 system of C16phNa and C12EO3, respectively, which is rather large. Cyro-TEM gave a direct image of wormlike micelles of the system. The present systems enrich the contents of anionic wormlike micelles systems.