HIERARCHICAL ORGANIZATION IN THE HYDROGELATION OF SURFACTANTS WITH UREA

Recently, a new self-assembly system based on surfactant and urea in water was discovered. Clinckspoor et al. 2022 were the first to describe that when mixing 37% urea and 200 mM cationic surfactant in water, a gel forms at room temperature¹. We expand this universe to anionic, zwitterionic and non-ionic surfactants, showing that the behavior is universal for different classes of surfactants. We show the formation of a rare lamellar hydrogel composed of lamellae arising from host-guest interactions between urea and the surfactant tail generating an inclusion compound. This organization presents long- and short-range ordering, which we show through SAXS and WAXS curves. We identified that the polar head of surfactant molecules significantly affects the interlamellar distance, the hydrogel formation kinetics, as well as its rheological parameters and the liquid-gel transition temperature.