Urea as hydrogelator of surfactants

• Published in: Journal of colloid and interface science Vol. 669; pp. 1015 - 1021
• Main Authors: Peçanha, Elaynne Rohem, Sabadini, Edvaldo
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2024
• Subjects: Adducts of urea; Hierarchical organization; Lamellar phase; Thermal transition; Thermal transition; Lamellar phase; Hierarchical organization; Adducts of urea
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2024.04.217

[Display omitted] The formation of adducts via urea interaction with distinct classes of surfactants (cationic, anionic, nonionic, and zwitterionic), leading to their assembly into lamellar structures and subsequent formation of hydrogels. The characteristics of these hydrogels are associated with both, the length of the alkyl chain, and the specific head group of the surfactant molecules. Characterization of adduct formation was conducted using Wide-Angle X-ray Scattering (WAXS), while Small-Angle X-ray Scattering (SAXS) was employed to probe the subsequent assembly into lamellar structures. The kinetics of hydrogel formation were assessed through rheological measurements and observed thermal transitions utilizing Differential Scanning Calorimetry (DSC). The investigation revealed a universal propensity for hydrogel formation across all surfactant classes. The formation arises from the interactions between urea molecules via hydrogen bonding, forming adducts around the surfactant chains. In sequence, the adducts self-assemble in lamellae. This process constructs the intricate three-dimensional network characteristic of the hydrogel. Furthermore, the kinetics of hydrogel formation, and their rheological properties under equilibrated conditions, were found to be significantly influenced by the nature of the polar head group of the surfactant molecules. This is the first evidence on the formation of adducts of urea with classes of surfactants. As they are common components in cosmetic, supramolecular hydrogels have high potential to be used in formulations.