AGGREGATION OF TETRADECYLTRIMETHYLAMMONIUM SALICYLATE

In the scientific context of molecular aggregation of surfactants, it is established that the first aggregation state of an ionic surfactant corresponds to spherical micelles.¹ In this work, we studied the micellization of the surfactant tetradecyltrimethylammonium salicylate (TTASal) using electrical conductivity (EC), isothermal titration calorimetry (ITC), and cryo-transmission electron microscopy (Cryo-TEM) at 298.2 K, to monitor how the counterion can alter the aggregate's curvature, forming wormlike micelles in the first aggregation state instead of spherical micelles. Our results highlight the atypical aggregation behavior of TTASal compared to classic cationic surfactants, such as TTAB. The EC results indicate that the degree of micellar dissociation reveals that only 10% of the counterions remain free in solution, and that the critical micelle concentration (CMC) occurs at 0.6 mM, with the process being driven by both enthalpy and entropy. Additionally, Cryo-TEM was used to monitor the morphological evolution of the aggregate during the transition between pre-micellization, micellization, and post-micellization states. This study reveals the complexity arising from nature's choice between forming spherical micelles or wormlike micelles.