pH-Tunable wormlike micelles based on an ultra-long-chain "pseudo" gemini surfactant.

Smart surfactant wormlike micelles (SWLMs), responsive to external stimuli, are a particularly recent area of development, yet highly promising, given the versatility of the materials but simplicity of the design. Here, we developed a pH-switchable wormlike micellar system based on a "pseudo" gemini surfactant (named as EAMA) formed by a mixture of N-erucamido-N,N-dimethylamine (UC22AMPM) and maleic acid with a molar ratio of 2 : 1, and compared the "pseudo" gemini worm system with UC22AMPM in the presence of hydrochloric acid (EAHCl). It was found that both maleic acid and hydrochloric acid can protonate the ultra-long-chain tertiary amine into a quaternary ammonium surfactant, thereby forming wormlike micelles; however, much stronger viscoelastic behavior was evidenced in the maleic acid system because one protonated maleic acid molecule can "bridge" two quaternized UC22AMPM molecules via electrostatic attraction. In contrast, the EAHCl system just shows a "mono" quaternary ammonium feature with a weak viscosity buildup. In addition, the maleic acid-based worm system was found to be more thermo-sensitive than conventional wormlike micelles, which also originates due to its "pseudo" gemini architecture.