Droplets Self-Born in the Dynamic Polymer for Generating Functional Coatings.

Droplet-embedded structures are useful in functionalizing polymer composites but difficult to prepare. Herein, we report a facile self-born method for creating droplets in supramolecular gels to mediate the material's functions. This method is based on the amplification of the defects of polymer matrices generated in curing by swelling-driving reconfiguration of supramolecular polymer networks. The system of poly(urea-co-polydimethylsiloxane) that can cross-link via hydrogen-bond interaction is used to demonstrate our concept. The elastomer matrices are prepared via a casting method and exhibit a heterogeneous structure with both strong- and weak-cross-linking domains. When these materials are swelled in solvents, solvent molecules concentrate in the weak-cross-linking domains to nucleate. With the reconfiguration of the matrices, the nuclei grow into pure droplets, leading to the formation of droplet-embedded structures. This method is applicable to different material systems. We also show that obtained coatings with such droplet-embedded structures exhibit various interesting properties including self-replenishment of the surface liquid, mechanoresponsiveness, and self-healing ability. Moreover, after the droplets are consumed, this method can be used to regenerate the droplet-embedded structure for refunctionalizing the materials. Therefore, we envision its applications in preparation of many useful polymer composites.