Thermally Activated Swelling and Wetting Transition of Frozen Polymer Brushes:a New Concept for Surface Functionalization.

Functional polymer brush coatings have great potential for various industrial applications thanks to their ability to adapt to environmental stimuli, providing tunable surface properties. While existing approaches rely on polymer-solvent interactions and their response to external stimuli, changes in the intrinsic physical properties of the polymer also play a critical role in modulating brush behavior. In this context, the melting transition of a semicrystalline oleophilic poly-octadecylmethacrylate (P18MA) brush coating is shown to drive a swelling and wetting transition upon exposure to various liquid alkanes. The top surface of this polymer displays a somewhat higher melting temperature than the bulk, enabling separate control of the bulk-driven swelling and surface-driven wetting transitions. Laser-induced heating enables reversible on-demand activation of both transitions with micrometer lateral resolution. These findings suggest a new concept of polymer brush-based functional surfaces that allow for controlled fluid transport via separately switchable surface barriers and bulk transport layers based on a suitable choice of polymer-polymer and polymer-solvent interactions.