The Design, Synthesis, and Characterization of Photochromic and Mechanochromic Functional Fibers

Mechanically responsive polymer materials have garnered significant interest due to their unique ability to respond to external forces, leading to groundbreaking applications in visual stress mapping and damage detection. However, their use in fibers remains relatively unexplored. In this study, a mechanoresponsive polymer is synthesized by incorporating a spiropyran (SP) mechanophore into a polyurethane backbone. Based on this mechanoresponsive polyurethane, mechanochromic fibers are fabricated via solution spinning. The fibers exhibits a clear color change from colorless to blue when subjected to external tensile stress or ultraviolet irradiation, triggered by the activation of the SP mechanophore. Furthermore, the mechanical sensitivity of the fibers can be tailored by adjusting the orientation of the polymer chains through hot stretching. Fibers subjected to higher pre-stretching during post-processing displayed a mechanochromic response at lower strain levels. Various pre-stretched fibers are then made into a barcode, which exhibits distinct dynamic information via color change during stretching. The innovative application of function fibers, capable of storing information through mechanochromic response, offers a novel approach to the development of anti-counterfeit fibers.