Photosensitivity Enhancement of Spiropyran-Containing Functional Molecules by Introducing Flexible Spacers and Their Application in Smart Color-Changing Textiles

Designing photochromic molecules to improve color sensitivity and reversibility of functional materials in the solidified state is still a major challenge. In this work, a series of photochromic molecules containing-spiropyran with different free volume groups have been designed and synthesized by introducing flexible spacers. The relationship of the photosensitivity and molecular free volume was investigated and the excellent reversible photoswitching molecules in both solution and solid state were obtained. The photosensitivity of the molecules increased with the increase of molecular free volume. The photochromic equilibrium time of the molecule with longer alkyl chain reduced from the 330 s to 60 s, and the recovering equilibrium time reduced from the 480 s to 40 s. The photosensitivity enhancement mechanism was explained by density functional theory and molecular volume calculations. The designed photochromic molecules were applied to polyester fabrics. The photochromic materials with excellent photosensitivity and good reversibility were obtained, which exhibited high contrast and sensitive reversible color changes. The photochromic materials have potential applications in the field of smart textiles, optical devices, anti-counterfeiting, etc.