Gelation properties of amino-acid-based bis-urea compounds in organic solvents and in the presence of surfactants

Self-assembled systems based on low-molecular-weight gelators (LMWGs) and micelle-forming surfactants are stabilized by non-covalent and non-interfering interactions. The simultaneous self-assembly of LMWGs and surfactants in a solution could lead to the formation of fibrillar networks with encapsulated surfactant micelles. In this study, the gelation properties of amino-acid-derived low-molecular-weight bis-urea compounds in water, various organic solvents, and surfactant solutions, including anionic surfactants sodium dodecyl sulfate and dodecylbenzene sulfonic acid, cationic surfactant cetrimonium bromide, and nonionic surfactants polysorbate 80 and octyl-β-d-glucopyranoside, were investigated. In the presence of surfactants, the nature of the linker of the bis-urea compounds influences the aggregation between gelator molecules. Compounds with cyclic and aromatic linkers effectively form gels at surfactant concentrations above a critical micelle concentration (CMC). The different fiber morphologies observed for surfactant gels based on imaging analysis suggest that the structure of the bis-urea compounds influences self-assembly. Rheological measurements revealed the solid-like nature of the gels and their high thermal stability. The viscoelastic nature of the surfactant gels offers potential use in various commercial applications, including home care products.