Thermally Stable Hydrogels From Cetylpyridinium Chloride‐Menthol System: Structure, Phase Evolution, and Mechanism

ABSTRACT A two‐component hydrogel was developed utilizing the cationic surfactant cetylpyridinium chloride (CPC) in a structure forming terpenoid alcohol menthol, which was realized and studied. At a critical concentration of 8 wt % in a 1:1 CPC:Menthol ratio, a stable hydrogel was formed. The gelation method, gel phase development, and its microstructure were investigated using spectroscopy, microscopy, and small‐angle x‐ray scattering techniques. UV–visible transmittance measurements revealed the phase development. The gel formed a lamellar organization with loosely packed bilayers stabilized by hydrogen bonding and hydrophobic interactions between CPC and menthol molecules. The SAXS pattern revealed a distinct crystalline form of the lamellar gel, indicating a stable phase characterized by alternating layers of crystalline and amorphous structures. Rheological studies highlighted the viscoelastic properties of the gel, while dynamic light scattering showed a mean vesicle diameter of approximately 70 nm before gel phase transformation. DSC and TGA revealed the thermal stability, phase transitions, and decomposition profile of the CPC:Menthol hydrogel.