Self-Assembly of Cinnamic Acid-Modified Chitosan Surfactants: Synthesis, Characterization, and Applications in Emulsification

Surfactants are extensively utilized in food, pharmaceutical, and industrial fields owing to their distinct interfacial properties. Nonetheless, their defects of poor biocompatibility and biodegradability impose a significant burden on the natural environment and on human health. Herein, we design cinnamic acid-functionalized chitosan (CC) as a biobased surfactant by substituting certain hydrophilic amino groups in chitosan molecular chains with the hydrophobic benzene rings of cinnamic acid. CC, exhibiting a surface contact angle close to 90°, demonstrates exceptional emulsification capabilities. Molecular simulations suggest that there is substantial interaction energy between CC and water, oil, and CC molecules. CC can be self-assembled into a gel network or stably distributed at the oil–water interface based on the interaction of polar groups with water and between hydrophobic groups with oil. Leveraging these interfacial characteristics, CC can be employed in the preparation of high internal phase emulsions (HIPEs), cell scaffolds with adjustable pore sizes, and aerogels for oil–water separation and dye adsorption. Notably, HIPEs loaded with curcumin and quercetin exhibit robust stability in gastric juice, intestinal targeted release, noncytotoxicity, and resistance to bacterial and mold growth even after 90 days. This work provides some references for the development of new biobased surfactants.