Simultaneous self-assembly of the biosurfactant di-rhamnolipid and a low molecular weight gelator

Abstract

Gelled lyotropic liquid crystals (G-LLCs) and gelled micellar solutions (G-MS) are promising soft materials for biomedical applications, combining mechanical stability with functional nanostructures capable of encapsulation and delivery. In such systems, the interactions between the gel network and the self-assembled surfactant structures significantly influence their properties. We investigated the simultaneous self-assembly of the biosurfactant di-rhamnolipid (Rha2C10C10) and the low molecular weight gelator 12-hydroxyoctadecanoic acid (12-HOA). We showed the dual role of 12-HOA as both gelator and co-surfactant at two different pH-values. Rheological measurements confirmed successful gelation, with enhanced elastic properties observed in both isotropic and liquid crystalline phases. SAXS and FFEM analyses reveal the coexistence of the gel network and the respective surfactant structure (LLCs or micelles). Furthermore, pH-dependent variations in fibre morphology suggest interactions between protonated rhamnolipid molecules and growing gel fibres, leading to structural defects and altered chirality. These findings highlight the complex interplay between surfactant self-assembly and gelation, providing design principles for tunable hybrid soft materials.