Advanced Functional Spiropyran‐Based Smart Materials with Rapid and Reversible Photochromic Response for Optical Sensing Applications

Abstract Stimuli‐responsive materials with optical adaptibility to external triggers are versatile for diverse applications. Among these, smart chromic materials with molecular photoswitching enable real‐time absorption changes indications, crucial for optical sensing, security, sensors, authentication, and anti‐counterfeiting applications. This current study presents an intriguing approach to develop spiropyran (SP)‐based molecular switches with rapid and reversible photochromism. Three dual‐responsive functional SPs (f‐SPs) dyes with varying SP moieties (1–3) are synthesized using straightforward chemical method. The responsiveness of f‐SPs to dual stimuli, such as organic solvents with varying polarity and light sources of different wavelengths (365 and 530 nm), is investigated. The increasing polarity of solvents (non‐polar to polar) facilitated stabilization of SP to merocyanine (MC) isomer. On contrary, upon irradiation with light sources, functional dyes exhibited significant, real‐time, and highly reversible changes in absorption and color. The rapid photochromic reversibility is facilitated within 20 s with increased SP moieties. Furthermore, f‐SPs are incorporated into Polydimethylsiloxane (PDMS) polymer matrix. The resulting composite films displayed exceptional photostability, rapid reversible photochromic responses, and reduced photo fatigue. Additionally, versatility of optical sensing approach is demonstrated by tailoring structural isomerization of these materials for photo‐patterning applications. This work paves way for advanced photochromic materials with cutting‐edge applications.