In Situ Interfacial Assembly of Dynamic Semi‐Interpenetrating Biopolymer Networks for Robust and Mechanically Adaptive Droplet Interfaces

ABSTRACT Mechanically robust yet rapidly adaptive interfacial films are difficult to construct from naturally derived polymers because of their limited structural programmability. Herein, we report an in situ stepwise interfacial assembly strategy that transforms β‐sheet‐rich silk fibroin (SF) and rhamnolipid‐modified chitosan (CS‐RL) into a strong, dynamic oil‐water interfacial network. The resulting interfacial film rapidly transforms from a spherical droplet geometry to distorted tubular shape within seconds without rupture, and exhibiting markedly enhanced dilational rheological properties. Abundant β‐sheet provides rigid hydrophobic nanodomains, while flexible SF chains and positively charged CS‐RL form a semi‐interpenetrating network through electrostatic attractions. Additionally, the hydrophobic interactions between β‐sheet domains and CS‐RL create load‐bearing reinforcing nodes and dynamic polymer junctions, enabling coherent network remodeling and efficient stress dissipation under deformation. This unique interfacial network contributes to stable interface and controllable interfacial releasing and transportation. Emulsions stabilized by this network remain stable after 15 months and show pH‐responsive drug release even under acidic conditions. The network also enables reversible transport of 200 nm nanoplastics across both oil‐water and oil‐oil interfaces. This work establishes a molecular‐topological design principle for creating strong, adaptive, and functional natural‐polymer interfacial films, offering broad opportunities for advanced soft matter systems with programmable properties.