Crystallinity‐Governed Liquid Wettability and Mobility on Solid Surface

ABSTRACT Control over liquid wettability and droplet mobility is essential for several emerging applications including open microfluidics, anti‐icing, self‐cleaning, and heat transfer. Existing strategies generally rely on permanent chemical modification or continuous external stimuli to regulate droplet spreading, pinning, and sliding. Here, we report a unified approach for reconfiguring wettability states and droplet mobility by regulating crystalline packing of a semicrystalline polymer. A phase‐transitioning polymer, poly(octadecyl acrylate) (PODAc), was incorporated into a porous polymeric coating, where melting and subsequent cooling pathways determine the extent of alkyl‐chain crystallization and interfacial polar functionality. Cooling in air or underwater generates reversibly switchable hydrophilic ( θ W ∼ 85°), hydrophobic ( θ W ∼ 104°), and amphiphobic slippery states across liquids with surface tensions of 22–72 mN m −1 . These distinct regimes enable programmable droplet spreading, pinning, and low‐friction transport without post‐synthetic chemical treatment or sustained external stimulation. Furthermore, reconfigurable wettability patterns enable guided liquid transport through spatially selective complete wetting or customized contact line frictional force.