Ex Situ pH‐Induced Reversible Wettability Switching for an Environmentally Robust and High‐Efficiency Stain‐Proof Coating

Abstract Developing superwetting coatings with environmental adaptability is critical for sustainable industrial applications. However, traditional anti‐wetting coatings often fall short due to their susceptibility to environmental factors (UV light, temperature, mold growth, and abrasion) and inadequate stain resistance in complex media. Herein, a durable ex situ pH‐responsive coating with reversible wettability switching, engineered by integrating hydrophobic polydimethylsiloxane and tertiary amine structures is presented. The resulting hierarchical micro‐nano surface structure, combined with a trapped air cushion, ensures low water adhesion and stable superhydrophobicity. Notably, after ex situ pH treatment, the modulation of surface N + content synergistically interacts with polydimethylsiloxane chains, enabling a controlled transition in surface wettability from 150° to 68.5°, which can spontaneously revert to a hydrophobic state upon heating and drying. This transition enhances stain resistance in both air and underwater environments, resulting in a 17.2% increase in detergency compared to superhydrophobic controls. Moreover, the coating demonstrates remarkable durability, with no staining, peeling, or mildew growth (grade 0) even after 1500 h of UV radiation and 28 days of mildew resistance testing. This work offers a highly adaptable and stain‐resistant coating for applications in building and infrastructure protection, as well as in smart textiles designed for multi‐media decontamination.