Spiropyran-based photochromic microcapsules as textile dyes: rapid color switching and stability

This research presents a comprehensive study on the development of high-performance photochromic textiles through microencapsulation of spiropyran dyes. The photochromic compound 1′,3′,3′-Trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-indolin] was successfully encapsulated within a melamine-formaldehyde resin shell via in-situ polymerization and applied to 100% cotton fabric using a screen-printing technique. The microencapsulated fabric demonstrated excellent photochromic properties, showing rapid and reversible color switching from colorless to intense purple upon UV irradiation (365 nm). Kinetic analysis revealed a coloration time of 85 ± 12 ms and a bleaching time of 45 ± 6 seconds. Most significantly, the microencapsulation strategy drastically improved photostability, with the material retaining 94.2 ± 3.1% of its initial optical performance after 100 accelerated UV-visible fatigue cycles, compared to only 32.5 ± 7.8% retention for non-encapsulated spiropyran. The developed system offers exceptional resistance to environmental degradation while maintaining efficient photochromic response, making it highly suitable for advanced applications in dynamic camouflage, adaptive fashion, wearable sensors, and responsive protective textiles. This work provides a robust framework for enhancing the durability and functionality of smart textile systems.