High-performance Hydrochromic Cotton Fabric Fabricated With CoCl2/waterborne Polyurethane for Air Humidity Detection

Abstract Hydrochromic materials has been a novel topic in the research of stimuli-responsive sensors and anticounterfeiting encryption. A high-performance hydrochromic cotton fabric is fabricated with CoCl2/waterborne polyurethane via hot-press method. Moisture sensing metal salt cobalt chloride is introduced into waterborne polyurethane via physical doping to induce hydrochromic phenomenon. The hydrochromic cotton fabric possess superior fastness due to the hydrogen bonds formed by hydroxyl group on cotton fabric and carbonyl group, urethane bond, ether bond in waterborne polyurethane. Meanwhile, the hydroxyl group on cotton fabric and waterborne polyurethane endow hydrochromic cotton fabric with excellent hydrophilicity and high humidity sensitivity. Air humidity could be easily detected by hydrochromic cotton fabric. The absorption of humidity in rainy days led to pink color, resulting in a blue shift at 512 nm. In contrast, hydrochromic cotton fabric turn to blue color below RH 59% in sunny days, leading to a red shift for up to 674 nm. Moreover, the hydrochromic cotton fabric exhibited eminent stability and cyclicity in response to either dry state or wet condition. Based on these excellent properties, hydrochromic cotton fabric fabricated with CoCl2/waterborne polyurethane are promising as smart sensors with potential application in sensitive RH detector, anti-counterfeiting technology and decorative coatings.