Injectable gel emulsions stabilized by tubular–fibrous networks self-assembled from an ursolic acid-based amphiphile

Gel emulsions stabilized by low-molecular-weight gelators (LMWGs) exhibit distinctive properties owing to the dynamic supramolecular networks self-assembled in the continuous phase. Innovating the molecular structure of LMWGs offers a promising strategy to endow gel emulsions with new functionalities. Herein, a novel ursolic acid-based amine oxide amphiphile (abbreviated as UA-6-AO) was synthesized, which acts as a highly efficient LMWG with a critical gelation concentration of 10 mmol·L −1 . At concentrations above this threshold, UA-6-AO stabilized gel emulsions by gelling the aqueous continuous phase, enabling adjustable oil volume fractions from 5 % to 70 %. Cryogenic transmission electron microscopy revealed that UA-6-AO self-assembled into a unique dual supramolecular network comprising hollow tubular structures approximately 25 nm in cross-sectional diameter, interwoven with flexible fibrous filaments about 5 nm wide and over 2 μm long, which are rarely observed in previously reported supramolecular hydrogels. This tubular – fibrous co-network imparted excellent viscoelastic and mechanical properties to both hydrogels and gel emulsions. Rheological analysis further demonstrated that the UA-6-AO-based systems exhibited rapid gel-sol-gel transitions under shear and complete recovery of the storage modulus upon strain removal, confirming self-healing behavior and injectability. This work highlights the potential of ursolic acid-based amphiphiles in constructing multifunctional gel emulsions, providing new insights into the application of natural triterpenoids in stimuli-responsive soft materials.