Fabrication of photochromic spiropyran-based coatings for smart color-tunable textiles

Photochromic materials have gained broad attention in a wide variety of fields due to their dynamic color transition properties. However, the high sensitivity and fast response of these materials still require further exploration. To address this challenge, a new photochromic spiropyran compound (SP-Br) was developed and successfully synthesized by incorporating a long alkyl chain into the spiropyran structure, achieving an optimal hydrophilic-lipophilic balance (HLB). The resulting SP-Br was applied to cotton fabric substrates through a simple screen-printing process, yielding a photochromic cotton fabric (SP-CF) with a functional coating capable of reversible color transitions. It is reported that SP-Br undergoes a reversible ring-opening/ring-closing isomerization when exposed to UV radiation at 365 nm. And with the color of the SP-CF reaching its maximum intensity within 30 s of UV exposure. After 10 color transition cycles, a slight reduction in the absorbance of the photochromic coated cotton fabric was observed; while its fatigue resistance remained virtually unaffected. Moreover, the screen-printed photochromic cotton fabric fabricated through this method exhibits several notable advantages, including rapid response time, excellent reversibility, significant color-changing ability, superior tunability in coloration, and reusability. These characteristics render the material especially promising for applications in fields like anti-counterfeiting printing, UV protection, information encryption, pattern switching, and other related domains.