The pH-responsive aggregates transition from spherical micelles to WLMs induced by hydrotropes based on dynamic imine bond
In recent years, the use of dynamic chemical bonds to construct stimulus-responsive micelle systems has received increasing attention. However, the current reports are all achieved by using dynamic chemical bonds to construct dynamic covalent bond surfactants, and the method of applying dynamic covalent bonds to hydrotropes has not been reported. In this study, a novel pH-responsive worm-like micelle system was constructed by mixing Cetyltrimethylammonium bromide (CTAB), 4-Hydroxybenzaldehyde (HB) and p-Toluidine (MB) at the molar ratio of 60 mM:40 mM:40 mM. The formation mechanism of the dynamic covalent bond hydrotropes and the rheological behaviors of the micelles system were investigated by rheometer, 1H NMR and Cryo-TEM. The results show that, as increasing the pH, the viscosity of the solution firstly decreases and then increases rapidly, the microscopic aggregates in the solution transform from spherical micelles to worm-like micelles (WLMs), and the solution behaves as a water-like fluid without viscosity to a gel system, which can withstand its own weight. The transformation of aggregates and rheology can be attributed by the formation of MB-HB-, which is one kind of dynamic covalent bonds hydrotropes. Moreover, the transition from spherical micelles to worm-like micelles in this WLMs system is reversible.