Downward Bound for Upward Leap in Surface Energy: A Strategic Approach to Crafting Durable, Adhesive, All-Purpose,...

In this work, we successfully transformed poly(vinyl alcohol) (PVA) thin films into all-purpose, self-cleaning coatings with unprecedented mechanical durability by using dimethyl sulfoxide (DMSO) as a casting or wetting solvent, followed by high-temperature curing. These coatings effectively cleanse themselves not only of liquid oil and solidified wax upon simple water action but also of ice with gentle airflow within several seconds, even after 100 cycles of destructive surface scratching. Surface-specific spectroscopic analysis revealed that, owing to DMSO acting as a hydrogen-bond-accepting capping agent, nearly all of the OH groups in the PVA coatings─both in the bulk phase and on the surfaces─were effectively prevented from forming hydrogen bonds and, simultaneously, thermodynamically driven to orient outward, minimizing surface energy in air. This resulted in a remarkably high surface coverage of free hydroxyl groups on the PVA coating (estimated as 0.84, dimensionless), thereby ensuring maximal surface hydration efficiency and a near-theoretical surface energy (∼69 mN/m) approaching that of water (72 mN/m). Furthermore, by casting fully and partially hydrolyzed PVA layers into bilayers on PTFE substrates, we successfully fabricated free-standing, self-cleaning adhesive films, extending the exceptional self-cleaning function of the PVA layers to a wide range of solid surfaces with varied surface energy and topography.