Hygroscopic and pH indicator-based polymer coating for fabrics with responsive discoloration

Humidity-induced discoloration from surface coating is promising, but the surface suffers from low stability, due to the lack of covalent interactions between pH indicator, hygroscopic components and fabrics. Here, we report a strategy to fabricate all-polymer-based, highly hygroscopic fabrics with humidity-induced discoloration and pH-induced discoloration simply by covalently coating/polymerizing a reactive pH indicator and a hygroscopic monomer onto fabrics. The resulting fabrics show remarkable and reversible discoloration from blue to yellow, upon increasing relative humidity. The high reusability of the discoloration has been verified by repeating moisture adsorption and desorption over 20 cycles, without obvious deterioration in the discoloration behavior. Moreover, the fabrics display discoloration behaviors upon contacting aqueous solutions and vapors at different pHs. The simple coating, significant and reversible color transition, and the high reusability enable the all-polymer-based, hygroscopic fabrics to be excellent candidates for humidity indication and pH indication.