Shape-Changing Core-Shell Bottlebrush Polymers as Stimuli-Responsive Interface Stabilizers

Abstract Shape-changing core-shell molecular bottlebrushes (CS-MBBs) are shown to be efficient, robust, responsive, and multifunctional interface stabilizers. MBBs homografted with poly(2-(N,N-diethylamino)ethyl methacrylate)-b-poly(N,N-dimethylacrylamide) (PDEAEMA-b-PDMA) side chains of sufficient lengths for both blocks exhibited reversible wormlike-to-stable globular shape transitions upon pH changes. Highly stable emulsions were formed by vortexing toluene and basic aqueous solutions of globular CS-MBBs even with rather low polymer concentrations (e.g., 0.01 wt %). Upon vortexing, CS-MBBs adsorbed onto the toluene–water interface, transforming into a Janus structure with PDEAEMA residing in toluene and PDMA extending into water. This mechanism was supported by interfacial tension measurements, PDMA partitioning between toluene and water phases, and interfacial wrinkling upon reducing the interfacial area. The emulsions were readily disrupted and re-generated by changing the pH. Using Nile Red as a model compound, we further demonstrated that globular CS-MBBs can also act as delivery vehicles. Consequently, we showed that CS-MBBs are responsive and multifunctional emulsifiers, capable of on-demand switching between strong interfacial binding and stimuli-triggered detachment from interfaces while serving as delivery vehicles, thereby opening fresh opportunities for MBBs in interface-related applications.