Smart <scp>pH</scp>‐responsive visual hydrophobic‐hydrophilic flexible switch based on branched polymer microcapsules

Abstract The integration of hydrophilic‐hydrophobic switching and color‐changing functionalities into textile materials creates a synergistic effect, meeting the demands of complex application environments. This paper presents an innovative and cost‐effective approach to generating a proton‐driven smart textile with dual‐functionality, capable of switchable wettability and color modulation, by combining pH‐responsive branched polymer microcapsules (PRBMs) with conventional textile materials. The prepared PRBMs are spherical with a rough surface, exhibiting dynamic swelling (diameter of 110 nm) in acidic aqueous solutions and reversible contraction (diameter of 70 nm) in neutral or alkaline aqueous solutions. Depositing PRBMs onto polyester fabric imparts pH‐responsive wettability to the fabric surface. As a result, the fabric displays hydrophobic in neutral or alkaline aqueous solutions (pH 7), exhibiting a contact angle greater than 140°, and becomes superhydrophilic when exposed to acidic aqueous solutions (pH 3), with a contact angle of 25° within 120 s. Notably, the fabric also undergoes significant reversible color changes under different pH levels while maintaining good water vapor permeability and breathability, suitable for the pH range of human skin. This one‐step strategy achieves a flexible, visible hydrophobic‐hydrophilic switch, marking a significant advancement in the field of smart textiles and promoting their further development.